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How to measure with an electronic tester (multimeter)

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Learning to read measurement data from a multimeter is easy when you understand how the device works. This article will teach you to read data from analog and digital multimeters.

Set the range on your analog multimeter. You must set the range above the maximum limit set for the device or outlet you are checking.

  • Determine if you want to test resistance or voltage. Typically, analog multimeters are not used to test current. Set the drive to the appropriate setting.
  • Set range. Your analog multimeter has several preset ranges on the scale you use. Set a range that is higher than the output of the circuit you are testing.
  • For example, standard household sockets have (in different countries) a standard output of 120 Volts (in Russia 220 Volts).
  • Your measurement should not exceed 120 Volts (220 Volts in Russia), but you should set a larger range just in case.

Multimeter

Multimeter (from the English multimeter), tester (from the English test - test), auto meter (from an ampervoltmeter) - a combined electrical measuring device that combines several functions.

The minimum set includes the functions of a voltmeter, ammeter and ohmmeter. Sometimes a multimeter is made in the form of clamp meters. There are digital and analog multimeters.

A multimeter can be either a lightweight portable device used for basic measurements and troubleshooting, or a complex stationary device with many features.

The name “multimeter” was first assigned specifically to digital meters, while analog devices are often referred to as “tester”, “avometer”, and sometimes simply “Tseshka” (domestic).

Content

The simplest digital multimeters are portable. Their bit depth is 2.5 digital digits (the error is usually about 10%). The most common devices with a resolution of 3.5 (the error is usually about 1.0%). A bit more expensive instruments with a resolution of 4.5 (usually accuracy of about 0.1%) and significantly more expensive devices with a resolution of 5 bits and higher (for example, the precision multimeter 3458A manufactured by Keysight Technologies (until November 3, 2014 Agilent Technologies) are also available. has 8.5 bits). Among such multimeters there are both portable devices powered by galvanic cells and stationary devices powered by AC power. The accuracy of multimeters with a resolution of more than 5 strongly depends on the measuring range and the type of measured value, therefore, it is agreed separately for each sub-range. In general, the accuracy of such devices may exceed 0.01% (even with portable models).

Many digital voltmeters (for example, V7-22A, V7-40, V7-78 / 1, etc.) are also essentially multimeters, since they are capable of measuring, in addition to direct and alternating voltage, also resistance, direct and alternating current, and A number of models also provide for measuring capacitance, frequency, period, etc.). Also to a variety of multimeters can be attributed scopmeters (oscilloscopes-multimeters), combining in one case a digital (usually two-channel) oscilloscope and a fairly accurate multimeter. Typical representatives of scopmeters are AKIP-4113, AKIP-4125, hand-held oscilloscopes of the U1600 series from Keysight Technologies, etc.).

The digit capacity of a digital measuring device, for example, “3.5” means that the display of the device shows 3 full digits, with a range from 0 to 9, and 1 digit - with a limited range. So, a device of the “3.5 category” type can, for example, give readings ranging from 0,000 before 1,999, when the measured value goes beyond these limits, switching to another range (manual or automatic) is required.

Indicators of digital multimeters (as well as voltmeters and scopmeters) are made on the basis of liquid crystals (both monochrome and color) - APPA-62, V7-78 / 2, AKIP-4113, U1600, etc., LED indicators - V7- 40, gas-discharge indicators - V7-22A, electroluminescent displays (ELD) - 3458A, and also vacuum-luminescent indicators (VFD) (including color) - V7-78 / 1.

The typical error of digital multimeters when measuring resistances, direct voltage and current is less than ± (0.2% +1 unit of the least significant bit). When measuring AC voltage and current in the frequency range of 20 Hz ... 5 kHz, the measurement error is ± (0.3% + 1 unit of the least significant bit). In the high frequency range up to 20 kHz, when measuring in the range from 0.1 of the measurement limit and higher, the error increases significantly, up to 2.5% of the measured value, at a frequency of 50 kHz it is already 10%. With increasing frequency, the measurement error increases.

The input resistance of a digital voltmeter is about 10 MΩ (it does not depend on the measurement limit, unlike analog ones), the capacitance is 100 pF, the voltage drop when measuring current is not more than 0.2 V. Portable multimeters are usually powered by a 9V battery. The current consumption does not exceed 2 mA when measuring direct voltages and currents, and 7 mA when measuring resistances and alternating voltages and currents. The multimeter is usually operational when the battery is discharged to a voltage of 7.5 V.

The number of discharges does not determine the accuracy of the device. The accuracy of measurements depends on the accuracy of the ADC, on the accuracy, thermal and temporal stability of the applied radio elements, on the quality of protection against external interference, on the quality of the calibration performed.

Typical measuring ranges, for example for the common M832 multimeter:

  • DC voltage: 0..200 mV, 2 V, 20 V, 200 V, 1000 V
  • AC voltage: 0..200 V, 750 V
  • DC: 0..2 mA, 20 mA, 200 mA, 10 A (usually via a separate input)
  • alternating current: no
  • Resistance: 0..200 Ohm, 2 kOhm, 20 kOhm, 200 kOhm, 2 MOhm.

Device Edit

An analog multimeter consists of a pointer magnetoelectric measuring device (microammeter), a set of additional resistors for measuring voltage, and a set of shunts for measuring current. In the mode of measuring alternating voltages and currents, the microammeter is connected to the resistors through rectifier diodes. Resistance is measured using the built-in power supply, and resistance measurement is greater than 1..10 MΩ from an external source.

Features and disadvantages Edit

  • Insufficient input impedance in voltmeter mode.
The technical characteristics of an analog multimeter are largely determined by the sensitivity of the magnetoelectric measuring device. The higher the sensitivity (less than the total deviation current) of the microammeter, the more high-resistance additional resistors and lower-resistance shunts can be used. This means that 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 device on the measured electrical circuit. Nevertheless, even when using a microammeter with a total deviation current of 50 μA in the multimeter, the input resistance of the multimeter in the voltmeter mode is only 20 kOhm / V. This leads to large errors in measuring voltage in high-resistance circuits (the results are underestimated), for example, when measuring voltages at the terminals of transistors and microcircuits, and low-power sources of high voltage. In turn, a multimeter with insufficiently low-resistance shunts introduces a large error in measuring current in low-voltage circuits.
  • Non-linear scale in some modes.
Analog multimeters have a non-linear scale in the resistance measurement mode. In addition, it is the opposite (zero resistance corresponds to the extreme right position of the arrow of the device). Before starting the resistance measurement, it is necessary to perform zeroing with a special controller on the front panel with the input terminals of the device closed, since the accuracy of the resistance measurement depends on the voltage of the internal power source. Small Scale Scale alternating voltage and current can also be nonlinear.
  • Correct polarity is required.
Analog multimeters, unlike digital ones, do not automatically detect voltage polarity, which limits their usability and scope: they require
  • the correct polarity of the connection in the mode of measuring direct voltage / current, and practically unsuitable for measuring
  • alternating voltages / currents.
    • ACV (English alternating current voltage) - measurement of alternating voltage.
    • DCV (English direct current voltage) - DC voltage measurement.
    • DCA (English direct current amperage - direct current strength) - measurement of direct current.
    • Ω - measurement of electrical resistance.

    Some multimeters also have the following functions:

    • AC current measurement.
    • Calling is a measurement of electrical resistance with an audible (sometimes light) signaling of a low resistance circuit (usually less than 50 ohms).
    • Generation of a test signal of the simplest form (harmonic or pulsed) for operational verification of the functioning of amplification paths and transmission lines (Ts4323 Prize, 43104).
    • Diode Test - Check the integrity of semiconductor diodes and determine their polarity.
    • Transistor test - checking semiconductor transistors and, as a rule, determining the static current transfer coefficient h21e (for example, testers TL-4M, Ts4341).
    • Measurement of electric capacitance (Ts4315, 43101, etc.).
    • Inductance measurement (rare).
    • Temperature measurement using an external sensor (as a rule, a K (XA) calibration thermocouple).
    • Voltage frequency measurement.
    • Measurement of high resistance (usually up to hundreds of megohms, an external power supply is required).
    • High current measurement (using plug-in / built-in current clamps).

    • Protection of the input circuits of the tester in the resistance measurement mode when the external voltage is accidentally applied to the input
    • Protection of the tester when the measurement limit is incorrectly selected (can cause damage to the measuring mechanism of the analog tester), and when connected to a voltage source in the current measurement mode (leads to leakage of short circuit currents, and can cause the ignition of current shunts and the entire multimeter). Protection is based on fuses and high-speed circuit breakers.
    • Auto power off
    • Display backlight
    • Recording of measurement results (displayed value and / or maximum)
    • Automatic selection of measuring limits
    • Low Battery Indication
    • Overload indication
    • Relative measurement mode
    • Recording and storage of measurement results

    Method 1 Read Data from an Analog Multimeter

    1. 1 Set the range on your analog multimeter. You must set the range above the maximum limit set for the device or outlet you are checking.
      • Determine if you want to test resistance or voltage. Typically, analog multimeters are not used to test current. Set the drive to the appropriate setting.
      • Set range. Your analog multimeter has several preset ranges on the scale you use. Set a range that is higher than the output of the circuit you are testing.
      • For example, standard household sockets have (in different countries) a standard output of 120 Volts (in Russia 220 Volts).
      • Your measurement should not exceed 120 Volts (220 Volts in Russia), but you should set a larger range just in case.

  • 2 Determine the maximum reading. The maximum reading is equal to the range that you set on your watch face. If you set the disc to 200 volts, then the multimeter scale shows 200 volts.
  • 3 Calculate the reading on half the scale. The reading on half the scale is equal to the Volt range divided by 2. If your multimeter is set to 200 Volts, then this reading indicates 100 Volts.
  • 4 Calculate the reading at various points on the scale. If your range is 200 Volts, and the arrow points to 0.72, then the reading is 0.72 times 200, or 144 Volts.
  • 5 Perform the check in accordance with the manufacturer's instructions.
  • Method 2 Read Data from a Digital Multimeter

    1. 1 Decide what you want to test with your digital multimeter. You can check voltage, current, resistance, capacitance and frequency.
      • Set the drive for the appropriate test.
      • Select a range that is larger than the output of the circuit or battery that you plan to test.
    2. 2 Perform the check in accordance with the manufacturer's instructions. The data on the digital display will provide you with the units you are checking. If you are testing voltage, and the digital screen shows 196, then the circuit has 196 volts output.

    External structure and functions

    Recently, experts and hams mainly use electronic models of multimeters. This does not mean that switches are not used at all. They are indispensable when, due to strong interference, electronic just do not work. But in most cases we are dealing with digital models.

    There are various modifications of these measuring devices with different measurement accuracy, different functionality. There are automatic multimeters in which the switch has only a few positions - they select the nature of the measurement (voltage, resistance, current) and the device selects the limits of measurement. There are models that can be connected to a computer. They transmit the measurement data directly to the computer, where they can be saved.

    Automatic multimeters on the scale have only types of measurements

    But most home masters use inexpensive mid-range accuracy models (with a bit depth of 3.5, which ensures an accuracy of 1%). These are common dt 830, 831, 832, 833 multimeters. 834, etc. The last figure shows the “freshness” of the modification. Later models have wider functionality, but for home use, these new features are not critical. Working with all of these models is not much different, so we will talk generally about techniques and procedures.

    The structure of the electronic multimeter

    Before using the multimeter, we will study its structure. Electronic models have a small LCD screen on which the measurement results are displayed. Below the screen there is a range switch. It rotates around its axis. The part on which the red dot or arrow is marked, it indicates the current type and range of measurements. Around the switch are marked on which the type of measurements and their range are set.

    Common multimeter device

    Below on the case there are slots for connecting probes. Depending on the model of nests, there are two or three; there are always two probes. One positive (red), the second negative - black. The black probe is always connected to a connector labeled “COM” or COMMON or which is labeled “ground”. Red - in one of the free nests. If there are always two sockets, there are no problems; if there are three sockets, you should read in the manual what measurements to insert a “positive” probe into into which socket. In most cases, the red probe is connected to the middle socket. This is how most of the measurements are made. The upper connector is necessary, if the current collected up to 10 A is measured (if more, then also in the middle socket).

    Where to connect the multimeter probes

    There are models of testers in which the sockets are located not on the right, but at the bottom (for example, Resanta multimeter DT 181 or Hama 00081700 EM393 in the photo). In this case, there is no difference when connecting: black to the socket labeled "COM", and red according to the situation - when measuring currents from 200 mA to 10 A - to the rightmost socket, in all other situations - to the middle.

    Sockets for connecting probes on multimeters can be located below

    There are models with four connectors. In this case, there are two sockets for measuring current - one for microcurrents (less than 200 mA), the second for current strengths from 200 mA to 10 A. Having understood what and why there is in the device, you can begin to figure out how to use the multimeter.

    Switch position

    The measurement mode depends on the position of the switch. There is a dot at one of its ends; it is usually tinted with white or red. This end also indicates the current mode of operation. In some models, the switch is made in the form of a truncated cone or has one pointed edge. This sharp edge is also a pointer. To make it easier to work, you can apply bright paint to this pointing edge. It can be nail polish or some kind of abrasion resistant paint.

    Position of the switch of ranges of measurements on a multimeter

    By turning this switch you change the operating mode of the device. If it stands upright, the appliance is turned off. In addition, there are the following provisions:

    • V with a wavy line or ACV (to the right of the “off” position) - AC voltage measurement mode,
    • A with a straight line - direct current measurement,
    • A с волнистой чертой — определение переменного тока (этот режим есть не на всех мультиметрах, на представленных выше фото его нет),
    • V с прямой чертой или надпись DCV (слева от положения выключено) — для измерения постоянного напряжения,
    • Ω — измерение сопротивлений.

    Также есть положения для определения коэффициента усиления транзисторов и определения полярности диодов. There may be others, but their purpose must be sought in the instructions for a particular device.

    Using an electronic tester is convenient in that you do not need to look for the desired scale, count the divisions, determining the readings. They will be displayed on the screen with an accuracy of two decimal places. If the measured value has a polarity, then the minus sign will also be displayed. If there is no minus, the measurement value is positive.

    How to measure resistance with a multimeter

    To measure resistance, move the switch to the zone indicated by the letter Ω. Choose any of the ranges. We apply one probe to one input, the second to another. Those numbers that appear on the display are the resistance of the element you are measuring.

    How to use a multimeter to measure resistance

    Sometimes the screen does not display numbers. If "jumped" 0, then you need to change the measurement range to a smaller one. If the words "ol" or "over" are highlighted, it costs "1", the range is too small and should be increased. That's all the tricks of measuring resistance with a multimeter.

    How to measure current

    To select a measurement mode, you must first determine the direct current or alternating current. There may be problems with measuring AC parameters - this mode is far from being available on all models. But the procedure, regardless of the type of current, is the same - only the position of the switch changes.

    D.C

    So, having decided on the type of current, set the switch. Next, you need to decide which socket to connect the red probe to. If you don’t even know approximately what values ​​to expect in order not to accidentally burn the device, it is better to first install the probe in the upper (leftmost in other models) socket, which is labeled “10 A”. If the readings are small - less than 200 mA, move the probe to the middle position.

    The situation is the same with the choice of the measuring range: first set the maximum range, if it turns out to be too large, switch to the next smaller one. So until you see the testimony.

    How to connect a multimeter to measure DC

    To measure the current strength, the device must be included in the open circuit. The connection diagram is given in the figure. In this case, it is important to install the red probe on the “+” power source and black touch the next element of the circuit. Do not forget when measuring that there is power, work carefully. Do not touch the bare ends of the probe or circuit elements with your hands.

    Alternating current

    You can try the AC current measurement mode at any load connected to the household power supply and determine the current consumption in this way. As in this mode, the device must be included in the open circuit, this may cause difficulties. You can, as in the photo below, make a special cord for measurements. At one end of the cord is a plug, at the other is a socket, cut one of the wires, attach two WAGO connectors to the ends. They are good in that they also allow you to clamp the probes. After the measuring circuit is assembled, we proceed to the measurements.

    AC current measurement with an electronic multimeter

    Turn the switch to the "AC" position, select the measurement limit. Please note that exceeding the limits may damage the device. In the best case, the fuse will burn out, in the worst case, the “filling” will be damaged. Therefore, we act according to the scheme proposed above: first we set the maximum limit, then gradually reduce it. (do not forget about the permutation of the probes in the sockets).

    AC measurement circuit

    Now everything is ready. First, we connect the load to the outlet. Can a table lamp. We insert the plug into the network. Numbers appear on the screen. This will be the current consumed by the lamp. In the same way, current consumption can be measured for any device.

    Voltage measurement

    The voltage can also be variable or constant, respectively, select the desired position. The approach to choosing a range here is the same: if you do not know what to expect, set the maximum, gradually switching to a smaller scale. Do not forget to check if the probes are connected correctly to the slots.

    In this case, the measuring device is connected in parallel. For example, you can measure the voltage of a battery or a conventional battery. We set the switch to the constant voltage measurement mode, because we know the expected value, select the appropriate scale. Next, touch the batteries on both sides with probes. The numbers on the screen will be the voltage that this battery gives out.

    How to use a multimeter to measure voltage

    How to use a multimeter to measure ac voltage? Yes, exactly the same. Only choose the correct measurement limit.

    Wire tapping with a multimeter

    This operation allows you to check the integrity of the wires. On the scale we find the sign of the calls - a schematic representation of the sound (look at the photo, but there is a double mode, and maybe only the sign of the calls). Such an image was chosen because if the wire is intact, the device makes a sound.

    The dialing mode on the multimeter measurement scale

    We put the switch in the desired position, the probes are connected as usual - in the lower and middle jacks. We touch one probe to one edge of the conductor, the other to the other. If we hear a sound, the wire is whole. In general, as you can see, using a multimeter is not difficult. Everything is easy to remember.

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