The measurement of various parameters of electrical circuits and their elements is performed by a specialized device, due to its versatility, the name - a multimeter.
The simplest models for functionality are comparable to autometers (abbreviated from the ampervoltometter), that is, the resistance and voltage strength are capable of measuring.
Modern advanced devices in addition can measure the parameters of radio components, such as capacitors, transistor performance, apply to determine the temperature and many other purposes.
Given that this is a common device among domestic masters and specialists engaged in the repair of electrical and electronic equipment, manufacturers produce increasingly functional models that combine more than 10 different measuring instruments in one case.
The multimeter is designed primarily for measuring the voltage, current and resistance force in the electrical circuit and on its separate nodes.
That is, the device in one housing combines a voltmeter, an ammeter and an ohmmeter.
Depending on the design and number of additional functions, it is used to check the integrity of the chain, control and determining the parameters of its elements.
Also a multimeter can measure the values of constant and alternating current.
Device and characteristics
In the standard version, the multimeter is a rectangular collapsible case with a control panel that protects the entire stuffing, including the power source (most often the Crohn type battery), from environmental impacts.
On its front side is a scale or a digital indicator, designed to display the measurement results.
Usually in the center there is a switch of modes of operation and measurement ranges.
For convenience on the case there are several holes of the sockets (more often than 3 or 4), intended for connecting two probe that are included in the kit.
One of the nests is designated as "COM", and it is connected to it by a minus probe, usually painted black.
The remaining nests are designed for the second probe, painted in red.
Depending on the specific range of measurements or type, the latter plug is inserted into the corresponding socket, each of which is signed by the symbol.
The incorrect connection of the probe leads to a breakdown of the multimeter right during measurements.
Modes and functions of multimeters
The multimeter has the following main operating modes:
- ACV - AC voltage measurement mode.
- DCV - DC voltage measurement mode.
- DCA - DC power measurement mode.
- Ω - measurement mode of the electrical resistance of the chain and its individual elements.
In addition to standard functions, the device can have one or more of the following additional modes:
- Measurement: AC power, electrical capacity and voltage frequency. Some models are able to measure high current values (by special current ticks), resistance. In the latter case, the multimeter requires connecting an external power source and is able to measure resistance with values of up to several hundred IOM. If the device supports working with an external thermocouple or other similar sensor, the owner appears the ability to measure the temperature. In rare cases, the device can determine inductance.
- A call is a mode designed to measure resistance, and in the case of its low value (most instruments, the threshold is 50 ohms) is triggered by the light or more often sound alarm. The integrity of the electrical circuit is checked.
- Test: transistors, diodes. Using the first function, you can determine the static current transmission coefficient, check the semiconductor transistor. The second function allows you to determine the polarity of the semiconductor diode and check its integrity in general.
- The generation of the test signal - allows you to check the functioning of transmission lines and amplifying paths.
As for additional features, the design of some models of multimeters can be provided:
- Overload protection - Provides automatic shutdown of the device and terminals of the circuit when measuring the voltage, the value of which exceeds the allowable. Also, multimeters are equipped with an overload indicator that is notified of exceeding the values of the measured voltage in a specific range.
- Protecting input circuits In the case when the multimeter is in resistance measurement mode, but voltage was applied to the probe.
- Protection against short-circuit current when trying to measure the voltage by a multimeter with an activated current force measurement mode. As a rule, such protection is implemented through circuit breakers or fuses.
- Battery discharge indicator.
- Built-in memory for recording and storing measurement results.
- AutoClug - increases the duration of the built-in power supply. The multimeter is independently disconnected after the expiry of a certain time in case it has not been used.
- Data registration - to detect episodic and hard malfunctions.
- Backlight of the scale or display - to work in conditions with an insufficient level of external lighting.
- Fixing results - for continuous display of the current or maximum value.
- Automatic installation of measurement limits. Unlike the manual selection of limits, where the master must independently control the position of the range of the range, the device independently selects the most suitable limit.
- Real-time clock is designed to automatically turn on the multimeter, to remove the testimony at a certain time.
Some modern professional digital multimeters, to all other, can boast the multilinguality of the interface.
Case material and shape
As a rule, the body of the portable multimeter is made of durable plastic that does not support combustion, often having rubberized inserts on the sides.
To protect against shock, the device can be placed in a rubber case.
In most cases, the housing has a pronounced rectangular shape with clear or rounded edges.
The housing of stationary multimeters is made of metal and plastic, its shape and appearance resemble a car radio, especially the front panel, where the display is located with all adjusting handles and control buttons.
Dimensions and weight of multimeters
For the convenience of using portable multimeters, their housing has an average size:
- Height: 100 - 200 mm
- Width: 60 - 100 mm
- Thickness: 20 - 40 mm
The weight of such devices is about 110 - 700 g.
The better the device is fulfilled, the more functions, the more he weighs.
Stationary multimeters feed from the household network 220 V.
Portable options have a built-in battery or batteries, such as AA or Krone type.
There are also models with connecting to an external power supply.
The duration of the multimeter operation of the batteries during its intensive operation leaves much to be desired (2 - 3 months), and therefore radio amateurs do not refuse to finalize the device, collecting a network power source independently to it.
Some models have the ability to pick up the power supply or batteries, in such cases the power supply is included in the kit.
The case of some models, especially Chinese production, is required to replace the batteries to fully disassemble, that is, remove the rear lid.
It is no secret that after such actions for the multimeter no longer applies to the warranty, which is worth considering when buying and clarifying this moment from the seller or manufacturer.
Test methods of digital multimeters, as well as general technical requirements are fully described in GOST 14014-91.
Each device must necessarily have a passport, which certifies the manufacturer's guaranteed technical characteristics and parameters.
In addition, the measurement funds (SI) registered in the State Racener correspond to all standards for them in the territory of the Russian Federation, and are officially applied to use.
To confirm registration in the registry, such multimeters receive an appropriate certificate.
Metric System and Error
Digital multimeters output the measurement results on the screen in the metric system.
At the same time, for instruments, there is such a concept as a bit, indicating how many full-fledged and limited discharges can be displayed on the screen.
This indicator is closely associated with the meter error, and for most simple models is 2.5 (error of about 10%).
For the discharge, 3.5 error is usually 1.0%, for 4.5 - 0.1%.
The latter value of the bit indicates that the display displays 4 full discharge (numbers 0 - 9) and 1 in a limited range (0 - 1), and this is the indications in the range of 0.0000 - 1,9999.
There are models with bit above 5.
In addition to a simple recording, where the amount of complete discharges is indicated, and then the limited range in the range of 0 - 1, there is another, the species X ^ Y / Z, for example, 4 ^ 5/6. Here 4 (x) indicates the amount of complete discharges, 5 (y) - the maximum incomplete discharge value, 6 (z) the number of values that can be taken incomplete category (0, 1, 2, 3, 4, 5 is 6 digits) .
Precision multimeters are found, the display of which has 8.5 discharges, but their error is strongly dependent both from the most measured parameter and from the particular subband. In the middle, the error for 5 or more discharge is 0.01% and lower.
Verification and calibration
Multimeters listed in the State Register are undergoing a mandatory primary and periodic verification with an interval of 1 year, which includes the metrological control of each measuring channel.
Primary multimeter calibration is still performed at the factory, while in the passport manufacturer specifies the maximum allowable range of deviations.
However, two identical instruments can be calibrated with different accuracy.
For multimeters, there is a calibration technique that requires the installation of the original parameter of the exemplary voltage - the VREF.
The most accurate measurement results are obtained under the condition that the exemplary voltage is ideal.
For the source of exemplary voltage at home, you can take the REF5050 chip by 5 V, the error of which is only 0.05%.
That is, the calibration of the readings of each value is carried out by connecting the instrument to the source of the same value with its known parameters and a small source error.
Types of multimeters and their price
On the principle of operation and the method of output of measurement results, the multimeter happens:
It is used mainly in conditions of severe radio.
This is a classic arrow autometer with a graded scale.
Recently, such devices have been practically ousted from the market due to sufficiently low measurement accuracy.
However, such a multimeter in work is extremely reliable and continued to be used to solve specific tasks, for example, to track smooth changes of the measured values.
It has high measurement accuracy, equipped with compact electronic components and a liquid crystal screen.
The base of the instrument is an analog-to-digital converter as part of the controller.
The microcircuit has a block for voltage analysis.
Small sizes, ease of use and the smallest error - the main advantages of such a multimeter, however, its filling is extremely sensitive to electromagnetic radiation, in particular, radio interference.
In one package, both of the instrument described above are combined.
The measurement result is displayed both on the LCD display and by an ordinary scale with an arrow.
The electronic multimeter requires a power source for its work, and therefore in turn happens:
With the connection to the external power supply or directly to the household network.
A network multimeter intended for professional activity is a high-precision multifunctional device capable of performing standard measurements, has a REL mode (relative measurements).
Desktop layout of the device in most cases implies its use also together with autonomous power sources, making such a multimeter mobile.
The cost is about 100 thousand rubles.
This niche occupies the absolute majority of multimeters.
Compact sizes, power is carried out by means of batteries or built-in batteries, which makes them mobile.
By the way, the low charge of the power supply leads to an increase in the error of the instrument.
This includes a pocket multimeter, characterized by extremely compact sizes (with palm).
Such a mini-multimeter is powered by AAA batteries, has accuracy in the range of 0.5% - 2.0%, depending on the measured value, and the display of maximum 3 ^ 1/2 (1999).
The cost is about 200 - 500 rubles.
The price of a full-size multifunctional professional model may exceed 50 thousand rubles, depending on accuracy.
According to constructive features and features, a portable multimeter happens:
Designed to work in explosive areas, for example, in pharmaceutical, refinery, chemical industries.
These are dust-absorbing and impassable models.
The cost is almost always exceeded 50 thousand rubles.
High-precision device for working in difficult conditions, often comes with a removable display, which improves its use in production facilities.
Price average 15 - 25 thousand rubles.
Allows you to determine the presence of voltage remotely.
For example, a multimeter with contactless voltage detection is suitable for checking the current in any wire, searching for the placement of wiring in the wall of the apartment.
Price - from 1900 rubles.
Combines the functions of an ordinary multimeter and cable tester.
The latter connects to the device through a special connector, serves for remote transversions without removing the insulation of cable lives and telephone lines.
The price is about 5 thousand rubles.
Another name is the current mites.
Designed to measure the electrical current values by contactless way without breaking and disruption of the circuit's performance.
At the top of the device there are ticks magnetic cable, which, closing around the cable, work on the principle of the simply transformer.
Price - from 600 rubles.
With thermal imager
Designed to find electrical equipment malfunctions, in particular, to detect heated zones and elements indicating the incorrect work of the latter.
The cost of the multimeter-thermal imager is about 30 thousand rubles and higher.
About thermal imagers Read here
With LCR-meter function
Devices that allow measuring resistance, capacity, inductance, goodness, attenuation coefficient equivalent to parallel and consistent resistance, tangent angle of dielectric losses.
Cost - from 8 thousand rubles.
In addition to standard functions, it is capable of measuring the angle of the closed state of the trimmer interrupter contacts and the number of crankshaft revolutions.
The price average is 2.5 thousand rubles.
With the measurement function of true SCZ
Devices with the function of the standard value (SCZ) allow you to determine the real efficient variable current values independently of the pulse distortion, and have a "True RMS" label.
Cost - from 1.5 thousand rubles.
When working independently defines the measured value and the measurement range.
Cost - 5 thousand rubles and higher.
It is capable of measuring resistance with large values, up to Gom.
The price for high-quality models - from 50 thousand rubles, depends on the upper limit of insulation resistance measurements.
As a rule, this device intended for installation in switchgear measures various variables of the three-phase AC network.
Price - from 3 thousand rubles.
Some portable and almost all stationary multimeters go with a USB interface.
These are devices with a connection to a PC, which, together with the program that comes in the kit, is displayed on the computer screen in real time the measurement results for registration, processing, analysis and printing.
What kind of multimeter to choose?
Choosing a multimeter for the house, there is no need to pay attention to the models made to the State Registry, as it affects their cost.
With domestic needs, a simple device will cope with the autometer functions worth 300 - 500 rubles.
The main thing is that his body is protected from dust and moisture (IP67), and the accuracy was not lower than 1%.
Some models are not equipped with a sound ring, namely, this feature is used by domestic masters most often, which should be considered.
Such a multimeter is also suitable for the repair of the car, and specialists engaged in professional vehicle power grids, it is better to purchase a special automotive option.
For professional activities, you need to choose a multimeter with minimal measurement errors.
It is important to pay attention to the presence of the required functions and not overpay, for example, for the built-in oscilloscope.
Each additional feature is a significant increase in the apparatus.
What you need to know about multimeters?
When operating a multimeter, until the start of each measurement, the measured value (measurement type) and the range is pre-installed.
In the case when the value of the measurement value is unknown, the device is installed on the maximum range, which is adjusted (decreases) after the first measurement.
The adjustment is performed in such a way that the range has been minimal for the resulting value.
Among the manufacturers of multimeters, attention deserve:
- Foreign - Elitech, Testboy, Fluke, Testo, Haupa, Top Tools, Jtc, Topex, Mastech, Trisco, Neo, Sturm, Ridgid, Proskit, EXTECH.
- Domestic - kW, tech, Megeon, Sez, Aktakak, Reante, FAZA.
What is a multimeter and what characteristics are important when choosing it
When creating or repairing electrical circuits, various measuring instruments are used that allow you to track all the necessary parameters. Multimeter This is a universal device, combines at least three of them - a voltmeter, an ammeter and an ohmmeter, to measure the voltage, current and resistance force, respectively. This already allows you to obtain a significant amount of information about the electrical path both in working condition and when the power is turned off.
What are the multimeters
Different generations of electricians can each explain to their own way what is a multimeter, since these devices are improved all the time. Some think that this is a fairly large and heavy box, while others are accustomed to miniature devices that are easily placed in the palm of palm.
First of all, all multimeters are divided into instruments on the principle of action - they are analog and digital. They are easy to distinguish between appearance - at the analog arrow dial, and in the digital - liquid crystal screen. Make a choice between them is quite simple - the digital are the next stage of the development of these devices and benefit from the analog in most indicators.
When only the first digital multimeters appeared, then they, of course, had certain design shortcomings, allowing you to say that this is a toy for lovers, but even then it was clear that digital devices have a huge potential and over time they will force themselves analog appliances.
In some cases, the use of analog multimeters is justified and now - they still have a number of advantages that are due to the design of the measuring instrument. Its main part is the frame with an arrow attached on it. The frame can rotate from the effects on the electromagnetic field - than it is stronger, the greater the angle of rotation.
Based on this, the main plus of an analog device is allocated - the inertia of the display of measurement results.
Similar words, this is displayed in the following properties:
- If you need not linear, but variable data (V, a or ω), then the arrow in real time will show their changes, visually demonstrating the entire amplitude of the signal oscillations. H, "Digit" In this case, the result will be shown stepwise - its value will be changed once in 2-3 seconds (it depends on the sensitivity of the device and its data processing rate).
- The shooter multimeter is able to identify the parasitic pulsation of the voltage or current. For example, if there is a permanent current value in one amp, but every few seconds it can briefly increase / decrease by 1/10 or 1/5, and then returns to the nominal. In this case, the digital tester may not show any signal changes at all, and the analog arrow will at least "slide" at these moments. The same will occur if there are persistent interference - if voltage fluctuations are already tangible - the digital multimeter will constantly show various data, and the analog simply averaged average - "integrated" value.
- To work a digital multimeter, you must need a power source, and the analog battery will only be needed if you turn on the module mode.
- For different devices there may be different extreme conditions. If digital protection cannot work without proper protection, for example, in a high-frequency electrical field, then for analog it is not a serious test - they can even serve as indicators of its presence.
All of the above refers not only to multimeters, but also to each analog measuring device individually - an ammeter, voltmeter or an ohmmeter.
Their main trump card is simplicity and functionality that is reflected in the distinctive properties of such devices:
- For the manufacture of such a device, it is not necessary to carry out a filigree work on the manufacture of electromagnetic coils and consolidate them in the housing, debugging and subsequent adjustment during operation.
The digital multimeter is simply an electric board in which contacts and control elements are depressed.
- The values that are displayed on the screen do not require "decryption" or interpretation, which is often with analog devices, which can be incomprehensible to a non-specialist.
- Resistance to vibration. If there is simply the same action on the digital devices of the shaking, then it affects the analog arrow very noticeably, and in some cases it can lead to a damage of the device.
- Unlike analog devices, the digital multimeter is independently calibrated each time it is turned on, so there is no need to constantly exhibit zero on the dial, which is a disease of any direction device.
This is not the entire list of possible benefits of a digital multimeter - only those that are clearly distinguished from an analog device.
As a result - if it is seriously engaged in electrical work, it is preferably in its arsenal to have devices of both varieties, since some possibilities are diametrically opposed.
How to measure digital and analog devices - in the following video:
What can be measured by a multimeter
The very first analog devices combined 3 instruments and it was possible to check the voltage (V), the current strength (A) and the resistance values of the conductors. At the same time, if there was no special problem in measuring the voltage for direct and alternating currents, then combine measuring instruments in one case to test the current and constant and alternating force - it turned out not immediately. It would seem, what's the matter of the days of the past days, but the fact is that there is still not all budget devices include such a functionality. As a result is a mandatory minimum that includes a multimeter today, it is a voltmeter for alternating and constant currents, measurement of resistance and strength of AC or DC.
Further, based on the class of the device, except for the voltmeter, an ammeter and an ohmmeter, there can also be frequency meters, temperature, diagrams for checking diodes (often combined with a sound signal - very convenient for use as a conventional transverse), transistors, capacitors and Other functions.
Not everyone and not always need all the functions listed, so the choice of such a device is an individual task that is solved on the basis of the planned front of work and the budget, which can be allocated to the purchase of the device.
Legend on the scale and front panel of the multimeter
It is not necessary to read the instructions for the multimeter to determine what it is capable - this information will be available if you simply look at its facial part with the installation of the use modes.
Since the functionality of the analog devices is smaller than that of digital, then as an example should consider exactly the last device.
On the overwhelming majority of models, the modes are set by means of a turning disk on which there is a label pointing to the scale of the scale deposited on the body.
The scale itself is divided into sectors, tags in which visually differ in color or visually divided into zones. Each of them indicates the parameter that measures the tester and allows you to set it sensitivity.
Review of the digital tester functional on video:
Standing and alternating current
The device's ability to measure the values of the AC and DC is visible by graphic marks or alphabetic notation. Since the overwhelming majority of testers are produced by foreign manufacturers, then the labels are affixed with Latin letters.
Alternating current is a wavy line or AC litera, which are decrypted as "Alternating Current". Permanent, in turn, marked with two horizontal lines, the top of which is solid, and the lower dotted. The letter designation is written as DC, which is decrypted as "Direct Current". These marks are set near the sectors, including current measurement modes (denoted by the literary "A" - ampere) or voltage (denoted by the Litera "V" - volt). Accordingly, for the constant voltage, the notation will look like the letter V with dashes near it or letters DCV. A variable voltage is indicated as a letter V with a wavy line or ACV letters.
Similarly, sectors are marked for measuring the current force - if the variable, then this is a liner A with a wavy line or ACA, and if the constant, then the letter A with dashes or litera ADA.
Metric system prefixes and measurement range
The sensitivity of the device can be configured to measure not only entire units, because of the electrical stakes are used by hundredths or even thousands of volt or amperes.
To correctly display the results, the circuit contains switches on shunts of various resistance and the device shows integer values with the following prefixes:
- 1μ (micro) - (1 * 10 -6 = 0.000001 from one)
- 1m (Milli) - (1 * 10 -3. = 0.001 from one)
- 1K (kilo) - (1 * 10 3= 1000 units)
- 1m (mega) - (1 * 10 6= 1000000 units)
If the device is set to the DC strength measurement (DCA) - a pointer, for example, will be deployed to 200 MA, which means:
- Maximum current, which can be measured in this position is 0.2 amps. If the measured value is greater, the device will show the output permissible limits.
- 1 unit shown by the tester equals 0.001 amps. Accordingly, if the device shows the figure, for example, 53, then it should be read as the current of the current in 53 milliamperes, which will look like 0.053 amps in a fractional decimal. Similarly, the KILO and MEGA prefix is used - if the regulator is set on them, the unit on the display of the device is a thousand or a million (these prefixes are mainly used when measuring the resistance).
If the device shows a unit, then for measurement accuracy, it is worth trying to reduce the range - instead of the value on the scale with the prefix "M", set the figure with the "μ" prefix.
Designations of various functions
Other functions of the multimeter can also be denoted by different signs or letters. At the same time, evaluating the functionality of the device, it must be remembered that the designations on the multimeter can relate to different sectors and carefully look at each icon:
- 01. Display Illumination - Light (Light)
- 02. DC-AC - This switch "reports" to the device which current will freeze - permanent (DC) or variable (AC).
- 03. HOLD - Key to fix on the screen of the last measurement result. Mostly such a function is in demand if the multimeter is combined with measuring ticks.
- 04. The switch tells the device that will be measured - inductance (LX) or capacity (CX).
- 05. Turning on the power. In many models there are no testers - instead, the power turns off the transfer of the pointer to the extreme top position - "12 hours"
- 06. HFE - a nest for testing transistors.
- 07. LX sector for selecting inductance measurement limits.
- 08. TEMP (C) - temperature measurement. To use this feature, you need to connect an external temperature sensor.
- 09. HFE - Enabling the testing function of transistors.
- 10. Enabling diodes check. Often, this feature is combined with a sound signal for electrocups - if the wire is intact, then the tester "beats".
- 11. A beep - in this case it is combined with the smallest resistance measurement limit.
- 12. Ω - When the switch in this sector, the device works in an ohmmeter mode.
- 13. CX sector - capacitors check mode.
- 14. Sector A - ammeter mode. The device is connected to the chain sequentially. In this case, the sector itself is aligned for constant or alternating currents, and which is measured depending on the switch "2".
- 15. FRIC (HZ) - AC frequency measurement function - from 1 to 20,000 hertz.
- 16. Sector V - to select the limits for measuring the voltage of the electric current. In this case, the sector itself is aligned for constant or alternating currents, and which is measured depending on the switch "2".
In addition to the swivel handle, there are sockets on the multimeter to connect the probe - by the master and touches the points in which the testimony should be taken.
Depending on the multimeter model, there may be 3 or 4 such sockets.
- 17. A red probe is connected here, if necessary, measure the current strength of up to 10 amps.
- 18. Nest for red probe. Used when measuring the temperature (the switch at this time is set to division 8), the current force is up to 200 mA (switch in the sector 14) or inductance (switch in sector 7).
- 19. "Earth", "Minus", "Common" wire - Black dipstick connects to this terminal.
- 20. The nest for the red probe when measuring the voltage of the electric current, its frequency and resistance of the wiring (plus a dial).
Conclusion - what to choose
It is difficult for a professional electrician to advise what functionality is needed from the multimeter to work, and even more so it makes no sense to recommend any particular model of the device - everyone will select the device, or even a few, under their needs. Well, for home use, oddly enough, but it is better to take the device close to "faded", but within reasonable limits in terms of cost. Read more on video:
The fact is that in this case it is difficult to predict which of the functions can come in handy over time. At least they will definitely need a call and a voltmeter, and if it is necessary to check the power of any device, then the ammeter. Further, in descending order, you can position the temperature, capacitors, transistors, field strength and electrical current frequency. In addition to the thermometer, these are all specific functions that are interesting only to the fans of radio electronics, and for the usual alignment they will simply increase the cost of the device.
What is a multimeter
Multimeter - This is an electrical device that can measure various parameters of electric current and radio elements. This is mainly voltage, resistance, current strength, capacitance capacitors, and also has some functions, such as conducting transversions, diodes and transistors. Some multimeter models may even measure the temperature of the radio elements using a thermocouple.
Digital multimeters Almost ousted analog multimeters due to their cheapness, convenience, as well as multitasking. Therefore, in this article we will talk about digital multimeters and their functions.
The digital multimeter consists of a display, the function selection switch (I simply call it a twist), nits where the probe is inserted, and the probes themselves.
In cheap multimeters, when measuring any value, you need to choose a measured range, therefore, you can often see the numbers as 2, 20, 200, and so on, which indicate the maximum measurement range.
Instruction on multimeter
On the front part we see the switch, with which we can choose the functions we need. Let's figure it out with the designations that are on the multimeter. Each function I marked the number for the convenience of perception.
one) Resistance Ω. This icon tells us that we are going to measure the resistance of a conductor or resistor.
2) Constant voltage = v. Having placed the switch to this icon, we can measure constant voltage.
3) AC voltage ~ V. Using this feature, we can measure the variable voltage value.
four) Measuring the gain coefficient of HFE transistors. I don't use it, because I have a special transistor device for this. In more detail about the gain, you can read in this article.
5) Capacitance Capacitors F. Everything is obvious. You can measure the container.
6) Measurement of current voltage current = a. We can measure the current voltage current.
7) Measure сAlternating voltage yels ~ a. With this feature, we can measure the strength of the voltage current. For example, this feature is useful when we need to know what the current flow flows into the chain when we connect the incandescent lamp or some other load to the 220 volt network.
eight ) Diode diode testing and sound integrity of conductors. Shows resistance if you measure the integrity of the conductors. When checking diodes shows the voltage drop on the PN transition. The charm of this feature is that if the resistance is laid less than 100 ohms (for different models it is different), the operating signal comes from the multimeter. A very convenient feature for checking diodes, as well as the integrity of wires and fuses. If you buy a multimeter, then take surely with a diode ring, otherwise such a multimeter will dramatically lose its functionality.
How to check the voltage multimeter
Measurement of constant voltage
As you know, the voltage is two types: variable and constant. Any multimeter we have at its disposal the functions of measuring constant and alternating voltage. To measure the voltage, we must touch the ties of the power source. As you can see, minus the power supply is desirable to connect with a minus multimeter (COM-black probe), and plus - with a red dipstick multimeter.
In order to measure the constant voltage, we must set the switch to the "= V" icon or the like. Let me measure the voltage on the battery, as the battery gives constant voltage.
For this, the switch on the multimeter is set to the DC measurement. For more accurate measurement, I put a range of up to 20 volts. We touch the shutters to the battery and see the value on the display. 1.28 volts, which for nickel-manganese batteries is considered normal.
In order to measure the voltage on any chemical current source, simply exhibit the range we need, then we look at the probe in their places (black on COM, red on V) and then touch the battery, battery or any other source.
Here, for example, I measure the voltage on the automotive battery.
You can also measure the voltage from the laboratory power supply unit, which gives constant current. Let's demonstrate how it all looks. I exhibit a 10 volt voltage on the power supply and measure this voltage by a multimeter.
But what will happen if we confuse polarity? That is, the red multimeter probe is connected with a minus, and a black probe with a plus? The digital multimeter in this case will simply show the "minus" sign.
In modern multimeters, this icon is already combined with the AC icon and looks like this:
Here, with the help of the function key, we ourselves choose which current will be measured: permanent or variable. Permanent current is denoted DC - Direct Current that in the literal translation from English - "Direct Tok".
Under the example below, I measured the voltage on the lithium-ion battery.
Measurement of alternating voltage
To check the voltage, we must set the functional selection switch to the "~ V" icon. I think you know that the voltage in the outlets of your home variable. Let's measure its meaning. As you can see, the multimeter showed 215 volts, although there should be something about 220 volts. This voltage still stacked in the working range, so everything is fine.
For a multimeter with an automatic range of ranges, we need to select the AC icon on the display of your device using the FUNC key. AC - Alternating Current, which is in the literal translation into English - alternating current.
In this way, the voltage is measured in the outlet. 228 volts, which is also quite normal.
How to measure current current multimeter
Measurement of current force in DC circuit
In order to measure the current strength in the chain, we must connect the multimeter into the chain rupture.
On simple digital multimeters it is necessary to transfer the red probe into the nest A or MA, which means amperes. You have not forgotten that the current is measured in amperes?
In order to measure Current strength in DC circuit We must set the switch to "= a". So, in our case, we will feed the voltage from the power supply to the computer fan.
We collect all this matter in our scheme, but instead of the incandescent lamp we will have this fan.
Since my power supply already has a built-in ammeter, you can compare the readings on the multimeter and on the power supply. As you can see, they completely coincide. The value of the current in the circuit is 0.18 amps.
On the coolest multimeter, we set some of these icons.
If you do not know how about the current strength in your chain should be about it, then you always put the switch to the largest range. In this case, at A. Let's check the current strength that can consume 12 volts incandescent lamp. To do this, set a voltage 12 volt on the power supply and put a multimeter into the chain break. That is, we do everything as it is for this scheme.
As you can see, the current in the circuit is 0.707 amps. This means that incandescent lamp at 12 volts consumes a current of 0.707 amps.
Measurement of current force in AC circuit
In order to measure the current strength in the AC circuit, we need to set the switch to the "~ A" icon. In steep multimeters, we put the function switch on some of these icons
And then we already choose using the "AC" function key, which indicates that we are going to measure the current strength in the AC circuit.
In order to demonstrate it, I will need a laboratory autotransformer (LATER).
This autotransformer allows you to obtain a variable voltage of a smaller value than in the 220 volt home network. I exhibit 12 volts voltage at the Latr output. Do not forget that these 12 volts are alternating voltage. I connect all this case according to the same scheme. By the way, the incandescent lamp is more powerful here, therefore, it will consume more current.
How to check the condenser multimeter
In order to Check the integrity of the condenser Multimeter, its container should be from 1 μF and higher. This trick is obtained only with analog multimeters, as well as with digital multimeters for selecting bands, such as such.
As you know, capacitors are polar and non-polar. Read more here. Polar capacitors have a large capacity, so they are easier to check for performance. How to do it? Let's look at the example below.
We have an electrolytic capacitor.
Multimeter put on the transverse mode and adapt to the leads to the condenser conclusions. Carefully watch the numbers on the scoreboard. They should increase as a capacitor charge.
As soon as I touched before the conclusions, the multimeter immediately showed this value.
In half a second
And then the value came out beyond the range of the range, and the multimeter showed a single one.
That is what can be said? At the most initial moment of time, a fully discharged capacitor behaves like a conductor. As it is charged with a current from the multimeter, its resistance grows until it becomes very large. Since the capacitor is charged, it means it is a worker. Everything is logical.
Capacitors of a smaller capacity and non-polar capacitors with a call can only be called for a short circuit between its plates. Therefore, another iron method is used here. Just measure the capacitor capacity). Here I measured the capacitance of the condenser on which 47 μF was written. Multimeter showed 48 μF. Or the error of the condenser, or a multimeter. Since Mastech multimeters are considered pretty good, then you will be spoken on the error of the condenser).
How to measure the resistance to the multimeter
So, we have a favorite digital multimeter
In order to measure resistance, we need to rotate the function selection switch to "measure resistance". This is our entire top row of green with the letter Ω. The letter "K" tells us that we are going to measure kiloma, and Bukovka "M" means that we are going to measure megaoms. Before the letter shows the measurement limit. If we have a unit on the display of the multimeter when measuring the resistance, then we switch to a larger limit.
How to check the permanent resistor
So, we have such a resistor.
We see on it the inscription "82R". It means that its resistance should be 82 Ohm. You can read more details about the marking of resistors in this article. To do this, apply one probe to one end of the resistor, and the other probe to another end.
As you see, the multimeter almost accurately showed the resistance value of this resistor.
How to check the variable resistor
Let me measure the resistance of the variable resistor. As you know, a variable resistor can change resistance to manually. The same applies to both trimming resistors - this is one of the variables of variable resistors.
This is his bottom view. Here we see the inscription 47 km. It means its resistance should be 47 kilomes between two extreme contacts.
With the help of the handle, we can turn it clockwise, or counterclockwise, thereby changing the resistance between the middle contact and two extreme contacts
Here is its schematic designation:
We put the probe on extreme contacts. Measure the full resistance of the variable resistor.
Hmm ... a little other resistance. Our variable resistor is too old, maybe therefore its resistance does not match the written on it. In order to check whether it works, turn the handle of the variable resistor until it stops counterclockwise and measure the resistance between the left and middle contact. It should turn out close to zero.
Turn the handle clockwise, but not to the end. We measure again resistance between the middle and left contact.
Measure the resistance between the middle and right contact.
In total, the result of the resistance of two extreme contacts should be. 12.2 + 27.6 = 39.8 almost everything is true. Consequently, the variable resistor is working.
Rules for measuring resistance
- Cress the probe with some force to the conclusions of the resistor. Thus, you eliminate the appearance of contact resistance, which, with a weak press, will be summed with the measured resistance.
- Do not measure stress resistance! Thus, you can damage the multimeter or get a blow to an electric shock!
- When measuring the resistance of the resistor on the printed circuit board, make sure that the board is de-energized. Then disappear one end of the resistor and then measure it resistance.
- Do not touch the conclusions of the resistor when measuring its resistance! The human body on average has a resistance of about 1 kiloma and depends on many factors. Therefore, touching the resistor conclusions when measuring the resistance, you make an error in measurement.
- If you want to measure the resistor resistance as accurately as possible, to clean it with the conclusions either by means of a knife or using the delicate sandpaper. In this case, you will remove the oxide layer, which in some cases makes a tangible error in measuring resistance.
How to nick multimeter
All modern digital multimeters have a call function. The transvelon is the same feature "Measurement of resistance", but only in this case the multimeter makes a squeak if the resistance is less than 100 ohms.
What is this feature required for? In order to check the integrity of wires, fuses, incandescent lamps, printed conductors, and so on. Very convenient and indispensable function in any multimeter. Most often, the call icon is combined with a diode ring. It looks like this:
For example, I want to sound the light bulb and find out if she is? To do this, I put the switch to the corresponding icon and touch the lamps to the lamp. The multimeter makes a treasure "piyip", and the indication of the resistance of the gas thread is displayed on the display of the multimeter. This means that the light bulb is alive, since the tungsten thread is not torn.
With your many years of experience in the field of electronics, I changed a lot of multimeters. I want to stop on two brands that I am very pleased and still happy in my difficult act.
Large display, convenient functionality, automatic shutdown function, inexpensive cost. If you are picked up by my site, you will see that I used these models of multimeters in your practice. They are very comfortable and durable. Yes, they have large dimensions, but it is worth it. Such a multimeter is very comfortable in hand.
Here is the link on Aliexpress. Try to take exactly the one in the photo above. Its cost in the range of 700-800 rubles.
Mastech, on my subjective look, makes decent multimeters for the price, quality and functionality. Yes, such multimeters are 2-3 times more expensive than the specimen above, but it really is worth it if you wish to dive into the world of electronics. Automatic range selection, many functions, small dimensions, convenient battery replacement and so on. The advantages of such a multimeter can be listed and listed.
As you saw, I have such a multimeter from this company. I can not not rejoice).
You can also watch it on Aliexpress Under this reference . There are many fakes, so be vigilant.
What is a multimeter?
Multimeter It is a multifunctional device that combines the functions of the ammeter, an ohmmeter and a voltmeter.
The shooting devices have almost ceased to be issued due to complexity in the measurement process, large errors, limited functions.
The device is widely used not only to solve professional tasks by electricians, but at home.
Combined models are on sale: digital with an additional shooting scale.
See also: Megaommeter - Device for measuring insulation resistance
All models, regardless of the type and cost, can measure the current, resistance and voltage. In addition to the standard set of functions, modern digital devices can measure:
- electrical capacity;
- voltage frequency;
- Electrical resistance with sound signals of low chain resistance, the so-called transvelon.
Also, using this apparatus, you can conduct tests of diodes, transistors.
ACV - alternating voltage;
DCV - constant voltage;
DCA - permanent current;
Ω - electrical resistance.
In the digital multimeter, the values are displayed on the LCD display.
See also: How to clean the wires from isolation
How to choose a multimeter
The modern market presents a wide range of devices of various price categories: from cheap Chinese to expensive American and German. The cost depends on:
- species - analog or digital;
If you are interested in inexpensive models, we recommend paying attention to the multimeters of Reante and Elitech. They can be purchased for 400-1500 rubles.
Similar main functionality, but the best assembly quality and additional features for comfortable work (for example, screen illumination) offer firms and Mastech.
The rating of appliances for professionals, in our opinion, is headed by the Fluke multimeters. Their cost at the time of writing article varies from 6800 to 96,000 rubles. The most fiscal option - Fluke 107. It has light weight - only 200 grams, memory function, a large display with backlight, runs from 3 AAA batteries. Basic error - 0.5%. In addition to standard measurements, with Fluke 107, you can check the integrity of the chain and diodes.
When buying should be focused on how often you plan to use the device and for what purposes. Cheap portable devices are designed for basic measurements at home and in the car.
By security class (CAT), we determine which networks are permissible to use:
I - low-voltage networks;
II - power supply;
III - distribution chains indoors;
IV - distribution chains on the street.
For ease of use, some models are equipped with a display illumination, an automatic shutdown timer, a battery indicator, protection with incorrect measurement limit, automatic selection of measurement limits, recording and storing measurement results.
How to use a multimeter
Before starting work, it is necessary to check the efficiency of the device itself. To do this, knock the ends of the probe among themselves. If the multimeter is working, there will be 0 on the display, or small thousandths of Ohm (00.1). When the probe is blurred, the value on the screen should be changed per unit.
Home Resistance is measured to verify the health of the electrical appliances. For a correct check, you need to know the reference indicator from the documentation for the device.
The measurement sector Ω is usually divided into several ranges (as a rule, 5-7), depending on the model:
- 200 ohms;
- 2000 Ohm;
- 20 com;
- 200 com;
To begin with, we choose the smallest range. Touch the arrows to both leaving the details and look at the display. If a unit is specified on the left side of the scale on the screen, it means that the incorrect range is selected and it must be switched to step forward and make me out again.
To read the readings are the most accurate:
- clean out the outputs;
The remnants of varnish or paint can affect the correct measurements.
- Perform measurements on a dry dielectric surface.
IMPORTANT: If you work in the range from 20 kΩ, then you can not touch the metal ends of the probes.
See also: How to choose a multimeter
Measurement of alternating voltage
Select the ACV sector and set the maximum value. If the upper limit of the previous range is less than the instrument reading, you can switch to a lower range. This will make more clear indications.
With this dimension, the polarity observance is not fundamentally.
Measurement of constant voltage
Select the DCV sector on the multimeter, set the largest range and in the measurement process gradually decrease it. Failure to follow this rule can lead to a breakdown of the multimeter.
If you confuse the probe, then the display will be a value with a minus sign. Therefore, it is important to observe polarity.
Measurement of current strength
We switch the device to the DCA sector, the scale, as a rule, has 4 bands:
- 200 μa;
- 2000 μa;
- 20 mA;
- 200 mA.
Using this function, the current is measured in the battery. To measure the probe, it is necessary to include in the rupture of the electrical circuit. Black dipsticks connect to a COM inscription connector (can be marked with the ground icon), red to the vΩma jack.
Properties for multimeters
Included with the instrument always provide proves that are metal rods with an isolated handle. Properties are needed to establish contact between the device and the subject for measurements.
The wires connect the probe and the device among themselves. When failure, the probes can be made independently. To do this, you should purchase metal pins, probes and wires in the market of radiostics or on the market. For convenience, you can make an additional set of probe with elongated wires or Crocodile connectors.
Digital multimeter with frequency measurement functions, checking bipolar transistors, temperature measurements and automatic measurement limit.
Combined Device C4324.
High accuracy multimeter Gossen Metra Hit 23s. Basic error 0.05% measured value + 3 youngest discharge
Pocket ampervoltmeter of the 1920s
Multimeter (from English. Multimeter. ), tester (from English. Test - test), Autometer (from the ampervoltimeter) - a combined electrical measuring device that combines several functions.
The minimum set includes the functions of the voltmeter, an ammeter and an ohmmeter. Sometimes a multimeter is performed in the form of toko-measuring ticks. There are digital and analog multimeters.
The multimeter can be like a light portable device used for basic measurements and troubleshooting, as well as a complex stationary device with a variety of features.
The name "Multimeter" first fixed precisely for digital meters, while the analog devices in everyday life are often referred to as "tester", "avometer", and sometimes "Tsheshka" (from the name of domestic devices of the series "TCHXX).
The most simple digital multimeters have a portable performance. Their discharge of 2.5 digital discharge (error is usually about 10%). The most common devices with a bit 3.5 (error usually about 1.0%). Also, a little more expensive devices with a bit 4.5 are also produced (accuracy usually about 0.1%) and significantly more expensive devices with a bit of 5 discharges and above (so, the precision multimeter 3458a produced by Keysight Technologies (until November 3, 2014. Agilent Technologies It has 8.5 discharges). Among such multimeters are found both portable devices that feed on electroplating elements and stationary devices operating from the AC network. The accuracy of multimeters with a bit of more than 5 strongly depends on the range of measurement and type of measured value, therefore stipulates separately for each subadapazone. In general, the accuracy of such devices may exceed 0.01% (even in portable models).
Many digital voltmeters (for example, B7-22a, B7-40, B7-78 / 1, etc.) are also multimeters, since it is capable of measuring other constant and alternating current voltage also resistance, power constant and alternating current, and A number of models also provides for measuring the capacity, frequency, period, etc.). Also, the varieties of multimeters include scopmers (oscilloscopes-multimeters), combining digital in one case (usually two-channel) oscilloscope and a fairly accurate multimeter. Typical representatives of Skopmers - Akip-4113, Akip-4125, Hand Oscilloscopes of the U1600 Series of Keysight Technologies Firms, etc.).
The discharge of a digital measuring instrument, for example, "3.5" means that the instrument display shows 3 full-fledged discharge, with a range from 0 to 9, and 1 discharge with a limited range. Thus, a device of type "3.5 discharge" can, for example, testify within 0,000 before 1,9999 When the measured value is released during these limits, switching to another range (manual or automatic) is required.
Indicators of digital multimeters (as well as voltmeters and scopmers) are made on the basis of liquid crystals (both monochrome and color) - Appa-62, B7-78 / 2, AKIP-4113, U1600, etc., LED indicators - B7- 40, gas-discharge indicators - B7-22A, electrolumine displays (ELD) - 3458A, as well as vacuum-luminescent indicators (VFD) (including color) - B7-78 / 1.
A typical error of digital multimeters when measuring resistance, constant voltage and current less than ± (0.2% +1 units of junior discharge). When measuring alternating voltage and current in the frequency range of 20 Hz ... 5 kHz measurement error ± (0.3% + 1 unit of junior discharge). In the range of high frequencies up to 20 kHz, when measured in the range from 0.1, the measurement limit and the above error increases, up to 2.5% of the measured value, at a frequency of 50 kHz, already 10%. With increasing frequency, measurement error increases.
The input resistance of the digital voltmeter of about 10 MΩ (independent of the measurement limit, in contrast to the analog), the capacity is 100 PF, the voltage drop when measuring the current is not more than 0.2 V. The power of portable multimeters is usually carried out from the battery with a voltage 9V. Current consumed does not exceed 2 mA when measuring constant stresses and currents, and 7 mA when measuring resistance and voltage variables and currents. Multimeter is usually operational when the battery is discharged to the voltage of 7.5 V [one] .
The number of discharges does not define the accuracy of the device. The accuracy of measurements depends on the accuracy of the ADC, on the accuracy, the thermo- and temporal stability of the radio elements used, from the quality of protection against external pressures, from the quality of calibration.
Typical measurement ranges, such as a common M832 multimeter:
- constant voltage: 0..200 mV, 2 V, 20 V, 200 V, 1000 V
- AC voltage: 0..200 V, 750 V
- Permanent current: 0..2 Ma, 20 mA, 200 mA, 10 A (usually through a separate entrance)
- Alternating current: no
- Resistance: 0..200 Ohm, 2 com, 20 com, 200 com, 2 mΩ.
Analog multimeter consists of a switch magnetoelectric measuring device (micro-vetermeter), a set of additional resistors for measuring voltage and a set of shunt for measuring the current. In the measurement mode of voltage variables and currents, the microammeter connects to resistors through rectifier diodes  . Resistance measurement is performed using a built-in power source, and the measurement of resistance is more than 1..10 MΩ from an external source.
- Insufficiently high input resistance in Voltmeter mode.
- The technical characteristics of the analog multimeter are largely determined by the sensitivity of the magnetoelectric measuring instrument. The higher the sensitivity (less current of the complete deviation) of the microammeter, the more high-level addition resistors and lower-level shunts can be applied. So, the input resistance of the device in the voltage measurement mode will be higher, the voltage drop in the current measurement mode will be lower, which reduces the effect of the instrument on the measured electrical circuit. However, even when using a microammetter in the multimeter with a current of complete deviation of 50 μA  The input resistance of the multimeter in the voltmeter mode is only. This leads to large stress measurement errors in high-level circuits (results are obtained), for example, when measuring stresses on transistors and chips, and low voltage sources.
- In turn, the multimeter with insufficiently low-voltage shunts makes a greater measurement error in low-voltage circuits.
- Nonlinear scale in some modes.
- Analog multimeters have a nonlinear scale in resistance measurement mode. In addition, it is reverse (zero resistance value corresponds to the extreme right position of the arrow of the device). Before starting the measurement of the resistance, it is necessary to install zero by a special regulator on the front panel at a closed input terminal terminals, since the accuracy of measuring the resistance depends on the voltage of the internal power supply.
- Loose measurement scale variable Voltages and current can also be non-linear.
- Requires the correct polarity of the connection.
- Analog multimeters, in contrast to digital, do not have the automatic determination of the polarity of the voltage, which limits the convenience of their use and scope: they require constant stress / currents in measurement mode, and practically unusable for measuring .
- ACV (eng. Alternating Current Voltage. - AC voltage) - measurement of alternating voltage.
- DCV (eng. Direct Current Voltage. - DC voltage) - measurement of constant voltage.
- DCA (eng. Direct Current Amperage. - DC strength) - DC measurement.
- Ω - measurement of electrical resistance.
Device 43104 with built-in frequency generator 1 and 465 kHz
Released from 1958 to the mid-1980s.
Some multimeters also features functions:
- Measurement of alternating current.
- Corresponds - Measurement of electrical resistance with sound (sometimes light) Low resistance signaling (usually less than 50 ohms).
- Generation of the test signal of the simplest form (harmonic or impulse) for the operational check of the functioning of amplifying paths and transmission lines (C4323 "Prize", 43104).
- Test diodes - checking the integrity of semiconductor diodes and determining their polarity.
- Test transistors - checking semiconductor transistors and, as a rule, determination of a static current transmission coefficient H 21E. (for example, TL-4M testers, C4341).
- Measurement of electric container (C4315, 43101, etc.).
- Inductance measurement (rarely).
- Measurement of temperature, using an external sensor (as a rule, thermocouple graduation to (ha)).
- Voltage frequency measurement.
- Measurement of greater resistance (usually up to hundreds of IOM; require an external power supply).
- Measurement of high current (using plug-in / built-in current ticks).
- Protection of the input circuits of the tester in the measurement mode of the resistance when the external voltage is random
- Tester protection If the measurement limit is wrongly selected (it may cause damage to the analog tester measuring mechanism), and when connecting to the voltage source in the current measurement mode (leads to the flow of short circuit currents, and can cause heat shunts and the entire multimeter). Protection is based on fuses and high-speed circuit breakers.
- Auto power supply
- Display backlight
- Fixing measurement results (displayed value and / or maximum)
- Automatic Selection of Measurement Limits (Auto-Ranging)
- Battery discharge indication
- Overload indication
- Real measurement mode
- Record and Storing Measurement Results
- ↑ Theoretical foundations of electrical engineering and electronics
- ↑ The direction of deviation of the frame of the magnetoelectric microammeter depends on the direction of the flowing current, so the direct measurement of alternating voltage and current is not possible: the arrow will tremble near the zero value.
- ↑ Egon Penker. UNIGOR 4P TYPE 226224 Equipment Metrawatt, BBC Goerz (eng.) . Radiomuseum.org. . - Typical values in mass domestic devices - 50..200 μA. High precision multimeters brand Unigor Austria made in their composition a more sensitive microammeter with a current of the total deviation of 40 μA (UNIGOR 3S) and even 10 μA. Date of handling: June 4, 2017.
- Benzar V.K. Dictionary-directory for electrical engineering, industrial electronics and automation. - 2nd ed., Per. and add. - MN. : Ex-school, 1985. - S. 7. - 176 p.