Precision digital multimeter Mastech MS8218 (Hardware). Multimeters so the same and yet so different

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Precision (high-precision) digital multimeter Mastech MS8218 with automatic range selection and TrueRMS function.

A small photo review, delivery set, basic functions and work with the device.

The MS8218 multimeter allows you to measure the root mean square values \u200b\u200b(TrueRMS) of the magnitudes of the force of the constant and alternating current, DC and AC voltage, resistance, capacitance of capacitors, signal frequency and duty cycle.

Contents of delivery:

  • multimeter Mastech MS8218,
  • set of probes,
  • cable for connecting to a personal computer,
  • software on CD,
  • set of batteries,
  • instruction,
  • bag-case with a belt,
  • packaging.

Packaging. A box made of thick cardboard with color printing:

Device bag and its contents. The bag is well made, with compartments for cables, a multimeter and instructions with a CD. It closes with a zipper; a belt is provided for easy transportation. When using additional probes with the device, it is possible to store everything in one place, this bag allows:





The MS8218 multimeter has a shock-resistant design, its body is rubberized:


Stand multimeter:




The multimeter is powered by six AAA batteries. There are also two fuses under the cover that provide current protection. In the µA, mA measurement mode (µA, mA - COM sockets) the maximum DC or AC input signal is 500mA. Fuse 0.63A / 250V. In measurement mode A (A - COM sockets) the maximum input signal is DC or AC 10A. Fuse 12.5A / 500V.Battery compartment, cover and screws:



Multimeter probes (CATIII 1000V 10A). The probes are equipped with protective caps and plugs. The protective caps have small slots in the cone. With the cap on the probe, you can measure the parameters of the circuit under voltage, thus minimizing the likelihood of short-circuiting something:





RS232C optical prot and data cable:




Physical parameters:

  • Rubberized body 200x100x40mm
  • The weight of the device is 600g.
  • Display: LCD, size 44x77mm, five-digit with indication of the maximum value of the measurement value of 50,000, with a graphical fifty-segment scale for mnemonic display of measurement values \u200b\u200band with display of the unit of measurement. It is possible to turn on the backlight in poor visibility conditions.
  • Multi-position rotary switch for operating modes of the device,
  • Function selection and power on keys,
  • Connectors: four, male.

Controls indication connectors:


  1. Measurement socket dBm, Hz, V, mV, capacitance, resistance, continuity of circuits and diodes;
  2. Common output jack COM;
  3. Current socket µA, mA;
  4. Current socket A;
  5. Rotary switch;
  6. Power off key;
  7. Key RANGE (Press the RANGE button to activate the manual range selection mode, the AUTO symbol on the display will disappear. To manually switch the range, press the RANGE button. To return to the automatic range selection mode, press the RANGE button for more than 1 second. AUTO will reappear on the display.)
  8. Key SELEСT (Pressing the SELECT button switches the measurement modes);
  9. Key WAKE (if the device goes into sleep mode and there is a need to continue measurements, pressing the key wakes up the device);
  10. Key MAX / MIN;
  11. Key REL ∆ (The relative measurement mode allows the user to measure the input values \u200b\u200bagainst a certain fixed value, called the reference. Almost any value of the input signal shown on the display can be taken as a reference, including signals in the MAX / MIN modes. To turn on / off the relative measurement mode, press the button REL∆ .);
  12. Key DATA HOLD (Hold the readings on the display. When you press the HOLD button, the readings on the display freeze and do not change when the input signal changes. The symbol appears on the display. To continue measurements, press the HOLD button again, the symbol disappears);
  13. Key LIGHT (Turns on the backlight of the device display for five seconds.);
  14. Key ~ Hz (Measurement of the frequency of sinusoidal signals when the measurement mode switch is set to one of the positions mV, V, μA, mA or A... Pressing the key again turns off the frequency measurement mode.);
  15. Display.

Display segments:

Display: LCD, size 44x77mm, five-digit with indication of the maximum value of the measurement value of 50,000, with a graphical fifty-segment scale for mnemonic display of measurement values \u200b\u200band with display of the unit of measurement.



  1. and). Capacity measurement indicator µF or nF;
    b). Current measurement indicator µA, mA or A;
    in). Measurement indicator dBm (unit of measurement of power in relation to the level of 1 mW, convenient way presentation in a compact form and very large and very small values \u200b\u200bof power, dBm is related to a watt and does not depend on impedance (impedance), serves to measure absolute power) or voltage in mV or V;
    d). Resistance measurement indicator MΩ, kΩ and Ω or frequency measurement MHz, kHz and Hz;
  2. Indicator for measuring the frequency of logical signals or measuring the relative duty cycle of pulses;
  3. Indication of modes of maximum, minimum and difference of measurements;
  4. Indicator for automatic selection of the measurement range;
  5. Indicator for manual selection of the measurement range;
  6. Manual measuring range indicator 5 , 50 , 500 , 1000 and 5000 ;
  7. Low battery indicator;
  8. Relative measurement indicator;
  9. Continuity indicator;
  10. AC voltage and current indicator;
  11. Negative polarity indicator;
  12. Constant voltage and current indicator;
  13. Indicator HOLD;
  14. Standby indicator (message “ Please Wait … "Is displayed when measuring the capacity in the range from 50 to 5000 µF causes of this phenomenon low speed measurement of containers of large quantities);
  15. Analog scale of measurements.Analogue scale provides visual indication of measurements, like an analogue instrument;
  16. Optical port activity indicator for data transmission over the interface RS-232C on a PC;
  17. Basic digital set of segments.

Working with the device.

When the probes are plugged into the current measuring terminals while the rotary switch is set to a mode other than the current measuring mode, the buzzer sounds and the display turns off.

Mode of root mean square measurements (True RMS).

In rms measurements of the input signal, the instrument calculates the RMS value of the input signal, which determines its power, and thus provides a more accurate measurement of signals than simply averaging the detected signal. This mode calculates both the variable and the constant components of the input signal, calculations are made according to the formula: v (DC2 + AC2), the result is accurate measurements.

ACV / dBm measurement. Maximum input voltage: 1000V AC!

Application area:

  • ACV Measurement of sinusoidal mains voltage in the range from 5.0000V to 1000V,
  • dBm Measurement in decibels measuring ranges from -11.76dBm to 54.25dBm.

The measurement accuracy depends on the frequency: 40Hz - 1kHz ± 0.5%, 1kHz - 10kHz ± 1.0%, 10kHz - 20kHz ± 2.5%.

Measurement procedure. Connect the black test lead to the COM connector and the red test lead to the V connector of the multimeter. Set the measurement mode switch to V ~ / dBm. Use the SELECT button to switch between V and dBm measurement modes.

When the device is turned on in dBm mode, its impedance value is shown on the display for one second. To change the impedance value in dBm mode, press the dBm- buttonΩ , while the impedance value changes in the sequence 4, 8, 16, 32, 50, 75, 93, 110, 125, 135, 150, 200, 250, 300, 500, 600, 800, 900, 1000, 1200 Ohm. The newly selected impedance is stored in the non-volatile memory of the multimeter, and will be turned on by default.

DCV / (AC + DC) V measurements. Maximum input voltage: 1000V DC voltage or DC / AC voltage !

Application area:

  • DCV DC voltage measurements in circuits and batteries,
  • (AC + DC) V Measurement of total (AC and DC) voltage in circuits.

Measurement range from 5.0000V to 1000V, accuracy ± 0.03%.

Measurement Procedure Connect the black test lead to the COM connector and the red test lead to the V connector of the multimeter. Set the measurement mode switch to DCV / (AC + DC) V position. Use the SELECT button to switch between measurement modes.

ACmV / DCmV / (AC + DC) mV measurements. Maximum input voltage: 500mV DC or DC / AC voltage !

Application area:

  • ACmV Measurement of low alternating voltages in circuits,
  • DCmV Measurement of small DC voltages in circuits,
  • (AC + DC) mV Measurement of low total voltages in circuits.

The measurement range is from 1.0mV to 500.00mV, the measurement accuracy for DC voltage is ± 0.05% and for AC measurements at a frequency of 40Hz - 1kHz ± 0.5%, at a frequency of 1kHz - 10kHz ± 1.0%, at a frequency of 10kHz - 20kHz ± 2.5%.

Measurement procedure. Connect the black test lead to the COM connector and the red test lead to the V connector of the multimeter. Set the measurement mode switch to mV position To switch between measurement modes, use the SELECT button.

Measuring the frequency of sinusoidal signals.

Applications: Frequency measurement of sinusoidal signals.

Measurement ranges from 5Hz to 2MHz (measurement range depends on the set measurement range).

Measurement procedure. Connect the black test lead to the COM connector and the red test lead to the Hz connector of the multimeter. Set the measurement mode switch to the mV, V position,μ A, mA or A. Press the ~ Hz button to turn the frequency measurement mode on or off.

Measuring the frequency of digital signals and measuring the relative duty cycle.

Caution: Never apply signals with a level that exceeds the limit values. When changing the measurement function, always disconnect the test leads from the circuit to be measured. Always keep your fingers behind the protective edges of the probes when taking measurements.

Application area:

  • Measuring the frequency of logic signals,
  • Measurement of the relative duty cycle.

Measuring ranges:

  • Frequency: 5.0000Hz - 2.0000MHz,
  • Relative duty cycle: 0.1% - 95%.

Measurement procedure. Connect the black test lead to the COM connector and the red test lead to the Hz connector of the multimeter. Set the measurement mode switch to Hz% position. Press the SELECT button to toggle between frequency and relative duty cycle.

Diode test.

Applications: quality control of diodes.

Measurement procedure. Connect the black test lead to the COM connector and the red test lead to the connector? multimeter.
Set the measurement mode switch to the diode test position:

  • Connect the black test lead to the cathode and the red test lead to the anode of the diode. Check the diode for good condition. Zero readings indicate a short-circuited diode. If the display shows OL, then the diode is open.
  • Connect the black test lead to the anode and the red test lead to the diode cathode. Check the diode for good condition. If the display shows OL, then the diode is good. Any other readings indicate a defective diode.

Resistance measurement.

Scope: measurement of resistance values \u200b\u200bof resistors and circuits.

Measurement range: from 0.01Ohm to 50.00MOhm, accuracy ± 0.1%,

Measurement procedure. Connect the black test lead to the COM connector and the red test lead to theΩ Ω and select the resistance measurement mode with the SELECT button.

To compensate for the resistance of the probes when measuring low resistances, use the relative measurement mode. If electrical noise interferes with the reading accuracy, shield the measurement object with a negative lead (COM). If your fingers touch the test leads during measurements, the electrical resistance of your body may affect the accuracy of your measurements.

Dial-up connections.

Applications: continuity of cables, harnesses, etc.

Dialing procedure. Connect the black test lead to the COM connector and the red test lead to theΩ multimeter. Set the mode switch to positionΩ and select the dialing mode with the SELECT button.

The response threshold is in the range from 0.01 to 60 Ohm.

Measuring the capacitance of capacitors.

Application: measurement of capacitance of capacitors.

Measurement range from 10.00nF to 5000mkF, accuracy: when measuring capacitance from 10.00nF to 500mkF ± 1.0%, when measuring capacitance from 500mkF to 5000mkF ± 2.0%.

Measurement procedure: connect the black test lead to the COM connector and the red test lead to the V connector of the multimeter. Set the mode switch to the position of measuring capacities.

When measuring the capacitance of capacitors in the range from 500 mkF to 5000 mkF, the operation time increases, the reasons for this phenomenon are low measurement speed of large capacities, while the message "Please Wait ..." is displayed on the display before the result is displayed.

Measurement of currents.

Warning:Never apply voltage to the input connectors. Make sure the multimeter is connected in series with the load. When making measurements on three-phase circuits, special precautions are necessary, since the voltage between phases is significantly higher than the voltage between any phase and earth. Do not apply currents to the input that exceed the maximum allowable values. Before connecting the meter to the measured circuit, turn off the power to the circuit.

Measuring currents in the rangeμ ANDand mA. Maximum input current: no more than 500mA.

Application area:

  • AC current: Measure current in AC circuits,
  • RMS current: Measurement of current in various circuits.

Measuring range: in modeμ A from 0.01 μ A to 5000.0 μ A, in mA mode from 1.0μ And up to 500.0mA. Measurement accuracy for direct current ± 0.15% and for AC measurements at a frequency of 40Hz - 1kHz ± 0.75%, at a frequency of 1kHz - 10kHz ± 1.0%, at a frequency of 10kHz - 20kHz ± 2.0%.

Measurement procedure. Connect the black test lead to the COM connector and the red test lead to the μ connector A / mA multimeter. Set the mode switch to positionμ А or mA and the SELECT button select the required current measurement mode. After turning off the power supply of the measured circuit, break the circuit and connect the multimeter probes to the open circuit. For DC current measurementμ A and DCmA connect the black test lead to the open point of the circuit with negative potential, and the red test lead to the point of the circuit with positive potential. To measure alternating voltage AC? A and ACmA, connect the black and red test leads to the open circuit of the measured circuit. For voltage measurement (AC + DC)μ A and (AC + DC) mA connect the black and red test leads to the open circuit of the measured circuit.

Measuring currentsin the range 10A. The maximum input current is no more than 10A.

Application area:

  • Direct current: Testing batteries and measuring currents in circuits,
  • AC Current: Measure current in AC circuits.

Measurement range: from 0.1mA to 10.00A Measurement accuracy for direct current ± 0.5% and for alternating current measurements at a frequency of 40Hz - 1kHz ± 0.75%, at a frequency of 1kHz - 10kHz ± 1.5%, at a frequency of 10kHz - 20kHz ± 5.0% ...

Measurement procedure. Connect the black test lead to the COM connector and the red test lead to the A multimeter connector. Set the mode switch to position A and select the current measurement mode with the SELECT button. After turning off the power supply of the measured circuit, break the circuit and connect the multimeter probes to the open circuit. To measure direct current DCA, connect the black test lead to an open circuit to a point of the circuit with a negative potential, and a red test lead to a point of the circuit with a positive potential. To measure alternating voltage ACA, connect the black and red test leads to the open circuit of the measured circuit. To measure voltage (AC + DC) A, connect the black and red test leads to the open circuit of the measured circuit.

Instrumentation publications

Some basics

Resolution, bit width and counts

The characteristic of a multimeter, called resolution, quantifies the degree of measurement accuracy that the instrument can make. By knowing the resolution of the measuring device, you can determine if it can detect a small change in the measured signal.

For example, if the digital multimeter has a resolution of 1 mV for a 4 V range, at 1 V, you can see a change of 1 mV (1/1000 of one volt). You would not buy a one-inch (or one-centimeter) scale when you need to measure to the nearest quarter inch (or one millimeter).

A thermometer that measures body temperature only in whole degrees will be of little use if we consider that normal temperature body is 36.6 ° C. You need a thermometer with a resolution of one tenth of a degree.

The terms "discharges" and "counts" are used to characterize the magnitude of the resolution of the meter. Digital multimeters are categorized by the number of counts or digits they display. A meter with 3 and 1⁄2 digit resolution displays three full digits ranging from 0 to 9 and one "half digit" which displays only "1" or remains blank.

Meter with 3 and 1⁄2 digit resolution displays up to 1999 counts of resolution. The meter with 4 and 1⁄2 digit resolution displays up to 19,999 counts of resolution.

The characteristic of the measuring device in the resolution counts is more accurate than in the digits. Modern 3-bit and 1⁄2-digit meters can be even higher resolutions up to 3200, 4000 or 6000 counts. For some measurements, instruments with 3200 counts provide higher resolution.

For example, a meter with 1999 counts will not be able to measure to one tenth of a volt if you are measuring 200 V or more. However, a 3200-count meter will display one tenth of a volt up to 320 V. If you are measuring up to 320 V, the resolution is no different from the more expensive 20,000-count meter.

Error

Uncertainty is the largest allowable error that occurs under certain operating conditions. In other words, it is a designation of how close the values \u200b\u200bdisplayed by the measuring device are to the actual value of the measured signal.

DMM accuracy is usually expressed as a percentage of the reading. An error of one percent of reading indicates that for a displayed value of 100 V, the actual voltage value can be anything between 99 and 101 V.

IN technical characteristics the range of digits can also be specified, which is added to the basic characteristic of the error. This value indicates the number of counts by which the rightmost digit on the display can change. Thus, the error from the previous example can be expressed as ± (1% + 2). Thus, for a displayed value of 100 V, the actual voltage will be between 98.8 and 101.2 V.

An analog meter is specified with an accuracy relative to full scale, not a displayed value. A typical analog meter error is ± 2% or ± 3% of full scale. An error of one tenth of full scale becomes an error of 20 to 30% of reading.

Typical basic error for a DMM is ± (0.7% + 1) to ± (0.1% + 1) of reading and below.

Ohm's law

Voltage, amperage and resistance in any area electrical circuit can be calculated using Ohm's law, which relates voltage, current, and resistance. It is known from the school physics course that voltage is equal to current strength multiplied by resistance (see Fig. 1).

Thus, if you know any two values \u200b\u200bin the formula, the third value can be determined. The digital multimeter uses Ohm's Law to directly measure and display resistance, current, or voltage values. Below you will learn how to use a DMM to get the information you need quickly.

Modern multimeters are multifunctional devices that allow you to quickly measure various electrical and radio quantities. In specialized retail outlets, there is a large selection of such devices, and the price for them can vary several times. To understand which multimeter is better to choose, you should decide on the requirements for it and understand what the differences are between different models.

Multimeter - a concept derived from the English multimeter (functional meter). It is an electrical measuring device that combines several functions. The multimeter can be produced as portable viewand stationary use. Portable instruments are designed for measuring and troubleshooting a wide range of measured values. Stationary devices, being highly specialized, are used for scientific and professional research. According to the principle of operation, multimeters are divided into two types:

  • analog;
  • digital.

Both types have advantages and disadvantages. But the digital tester is more popular. This is due to the more visual obtaining of the measurement result in comparison with the analog type and more comfortable work with him.

In their work, analog devices modify the received signal in terms of current strength, and then measure this value. Digital ones, using integrated amplifiers in circuitry, convert the signal into a potential difference, and only after that the parameters are measured.

Analog device type

The first instruments for measuring parameters were pointer devices. In their design, an electromechanical head was used, which is a frame located in an alternating magnetic field. A signal was applied to this head through a fixed value resistance. As a result, the arrow in the frame deflected to a certain position, depending on the current strength. The range of movement of the arrow was limited and graduated with numbers, which denoted the calculated values \u200b\u200bof one or another quantity.

The technical parameters of the switch device are largely related to the sensitivity of the electromechanical head. The main advantage of this type of tester is its ability to inertia and immunity to external interference, which is especially important for measuring DC voltage and resistance values. When measuring a constant voltage, the multimeter will integrate the result to the rms value. Additional resistances are used to expand the range.

When determining which multimeter to choose for a home or car, a small percentage of preference is given to pointer instruments. It's connected with main characteristic tester - accuracy class.

First of all, "switchmen" are used not for the sake of accuracy, but for the sake of convenience: it is more comfortable to observe a deflected arrow than to look closely at the numbers. Such measurements are needed for a specific type of operations that are little used in the everyday sense.

For analog devices, the accuracy class is indicated by a number - for example, 0.01 or 4.0. This number represents the greatest inaccuracy of the instrument. It is expressed as a percentage of the maximum indicator measured in the selected interval of work. In the voltmeter mode, which has a measurement interval from zero to thirty volts, an accuracy class equal to one indicates that the inaccuracy when the arrow is deflected anywhere on the scale will not exceed 0.3 volts. This means that the rms reading of the instrument is 0.1 V.

Such a value when measuring low voltages will be a very large number of probable calculation errors. For example, for a signal with an amplitude of 0.5 volts, it will not work to get an accurate result, since the error will be 60%.

You should also take into account the following point: manufacturers do not always indicate the error for all types of measurements. But it is not difficult to determine it yourself. The accuracy class of the instrument is always matched to the scale division. Therefore, if the magnitude of the error is unknown, then its value is calculated as half the price of the smallest division of its scale.

Digital view device

The digital multimeter device is based on the use of an analog-to-digital conversion (ADC) microcircuit. It is an unpackaged element (crystal) that is soldered directly to the device board. The combination of an ADC with a digital display makes it possible to achieve a high class of accuracy in testers of this type. The device works by comparing the received signal with a reference voltage. The stability and accuracy of the readings depend precisely on the setting of this reference voltage and the stability of the parameters used in the design of radioelements.

Unlike analog testers, the main characteristic of digital multimeters is their capacity. For example, when choosing a digital multimeter with a digit capacity of 2.5, the obtained accuracy of the instrument readings will lie within 10%. There are devices with a capacity of 3.5; 4.5; 5 or more. The price of devices grows depending on the bit class: the higher it is, the more expensive the price will be. In this case, the value of the bit depth depends not only on each type of measurement separately, but also on its sub-range.

So, the average inaccuracy of digital multimeters when measuring impedance, DC voltage and current is ± 0.2%. When measuring a sinusoidal signal in the frequency range from 18 Hz to 5 kHz, the measurement inaccuracy is ± 0.3%. In this case, with an increase in the signal frequency, the measurement inaccuracy increases. This means that for frequencies up to 20 kHz, the measurement error increases to 2.5% of the value of the measured parameter, and at a frequency of 50 kHz it will already be 10%.

To ensure the operation of the multimeter, a KRONA battery with an operating voltage of nine volts is usually used. The device itself gives measurements when this value is reduced to 8 volts, after which the results will not correspond to reality. To avoid this, the devices are equipped with an indicator that shows a blinking battery on the display, which indicates the need to replace the battery.

Therefore, before choosing a digital multimeter for the home, it is important to decide what accuracy of the device is required for measurements. An optimal and inexpensive device will be a device with a bit depth of at least 3.5 - that is, with an accuracy of about 1.0%.

Features and characteristics

Among themselves, multimeters differ not only in the principle of operation, but also in the ability to measure certain quantities. Any multifunctional device has basic and additional functions.

The basic modes of operation include:

  • ammeter;
  • voltmeter;
  • ohmmeter.

In this case, both variable signal values \u200b\u200band constant ones can be measured. Additional modes make it possible to check the device capacity, inductance, frequency, temperature and p-n junction... Some meters are mobile oscilloscopes so you can see the waveform as well. But not always a cheap device has few functions. Devices with basic functions are often more expensive than other functional tester. This is due to the quality of the measurement and the type of protection used in the device.

When selecting a tester, you should pay attention to the following functions:

A quality multimeter should be equipped with protection for measurement modes. In the case of an incorrectly selected level, it must protect the device from possible damage. In addition, demanded functions are auto power off, memory of measured results, automatic selection testing limit and highlighting. It is worth paying attention to the shape of the tester and what material the body of the device is made of.

Criterias of choice

Approaching the decision about which good multimeter is better to choose, you need to outline the necessary selection criteria. This, as a rule, is the price of the device and the tasks for which it is purchased. If you plan to use it for domestic needs, an inexpensive multimeter with basic operating modes will be the right option, which will allow you to quickly take measurements, investigate the integrity of the wiring or calculate how much the battery in the car is discharged.

Professionals dealing with repairs or research activities, it will be better to choose the device in accordance with their type of activity. For them, a highly specialized oscilloscope-type multimeter will most often be in demand. Electricians, if necessary to work with electrical installations, will need not only high accuracy, but also protection, the degree of which corresponds to the rules of electrical safety.

Popular manufacturers

The choice of products in retail outlets is very large. When choosing a device for measurements, attention is not least paid to the name of the manufacturer. Famous companies guarantee: compliance with the declared characteristics, warranty and post-warranty support. The most famous companies are:

  • Mastech;
  • YATO;
  • Fluke;
  • UNI-T;
  • Laserliner;
  • TOPEX.

But there are other manufacturers whose testers' models are also up to par. Famous brands try to improve their products, use quality parts and meticulous adjustment of measurement parameters, which invariably affects the final cost.

A multimeter is an affordable device that is in demand not only by professionals, but also by ordinary people. The right device will last for many years. Allocating a budget for the purchase, before buying a multimeter, you should decide on the following issues:

Since, when used in a domestic environment, a high measurement speed and clarity are required from a multimeter, choosing between an analog and a digital device, the latter is preferred. There are models that do not exceed the size of a pack of cigarettes, and this gives additional advantages when using or carrying them.

Measuring instruments with electronic filling and manual control used in electronics and electrical engineering to measure the properties of an electric current circuit are called multimeters. The devices can measure various parameters, including voltage, current, resistance, capacitance, determine the polarity of the terminals, as well as the pinout of transistors and many other parameters.

Device

Multimeters consist of a plastic case in which the electronic filling is located, a power supply, a screen, or an arrow scale, a regulator with which you can choose the type and interval of measurements.

To make it convenient to measure the parameters of the circuit, the device is equipped with special probes, which are made in the form of pointed metal rods with insulated handles. These probes are connected to the multimeter with plugs through flexible conductors.

Classification and features

All multimeters, or as they are also called, testers, are divided into two classes:

  • Analog.
  • Digital.

Let's take a closer look at each class of measuring devices.

Analog multimeters

Testers of the classic type, which have been used for a long time, with a dial gauge, belong to the analog class of instruments. They are already practically superseded by digital devices.

The housing has a built-in screen with a graduated scale and an arrow. Measurements are carried out using electronic components.

Such devices do not have high measurement accuracy, but they are quite reliable in operation. With the help of them, it is possible to measure parameters with strong interference from radio waves, in contrast to modern digital devices.

Digital multimeters

Digital testers are highly accurate instruments. They are equipped electronic components compact size, convenient digital liquid crystal display.

The design of the digital device is based on a controller with an analog-to-digital converter. The microcircuit contains a block that analyzes the voltage.

With the help of such devices it is possible to measure parameters with the smallest error, they are convenient in operation and have small dimensions. Their main disadvantage is increased sensitivity to radio interference and other electromagnetic radiation.

Accuracy classification

Multimeters have different measurement accuracy depending on the instrument version. The simplest are 2.5-bit testers. This is equivalent to a measurement accuracy of 10%. The most widely used models are multi-testers with an accuracy of 1%. Also, such devices may have lower accuracy. Their cost depends on the accuracy. The higher the measurement accuracy, the more expensive the device is.

Scope of application

These versatile instruments allow you to measure several parameters of AC and DC: voltage, current, resistance, while specialized instruments such as ohmmeters, ammeters and voltmeters can only measure one specific circuit parameter.

Multimeters are widely used in industrial, electrical engineering, electronics, engineering calculations, during repair and maintenance work. Together with control lamps, multitesters are used for finishing work, during installation and connection electrical network... The use of multimeters makes it possible to ensure a high-quality installation of electrical equipment.

Preparing the device for operation

Before starting measurements, the device must be prepared for work, collect all the elements, connect flexible conductors with probes to the terminals of the case. Most often, when carrying out many measurements, for example, when monitoring the internal electrical systems of a building, a certain algorithm for connecting a multitester is tried on:

  • The black neutral conductor is inserted into the COM socket.
  • The red wire (phase) is inserted into the socket located above the black one to measure voltage, current (no more than 200 mA) and resistance.

Warning: make sure the red wire jack is marked with a “V”. The red plug cannot be inserted into the third socket (it serves to measure DC current up to 10 amperes) when measuring AC current from a household network, as this is life-threatening.

Checking the circuit with a digital multimeter

Testing of circuit parameters is carried out to control the condition of the insulation of wires, their integrity, the quality of connections. The chain ring is made by two methods.

Method for measuring circuit resistance

Set the regulator to the resistance measurement mode for any reading value.

Apply the test leads to the wires of the circuit under test. If "1" appears on the screen, then the wires have no contact with each other, that is, the resistance between them is greatest. It can also indicate that the circuit is broken, or about correct assembly, no short circuits and faulty wire insulation.

If a certain value is displayed on the display, then a current flows through the circuit. This indicates that there is a short circuit in the wires, or indicates a good assembly. In this case, the lower the resistance value on the display, the better the assembly.

The procedure for ringing a 3-core cable for the presence of a short circuit.

Conductivity measurement method

Set the regulator to circuit test mode (not available on all instruments).

Voltage detection and ringing ground

To measure voltage and monitor the ground loop, use the toggle knob to set the AC voltage mode to a value greater than the measured voltage.

Voltage detection

Insert the tips of the test leads into the sockets of the mains socket.

The voltage value appears on the screen. The polarity of the probes for connection is not important, since when connecting probes with reverse polarity, the measured value will also be displayed on the screen, only with a minus sign.

The voltage in the network is constantly changing, and most often differs from 220 volts, but this is not a breakdown or malfunction.

Ringing ground

To check the ground loop, one probe is applied to the ground, the other to the phase.

When dialing, difficulties often arise. Ground circuit - - the phase is called with almost equal voltage values. Therefore, it is difficult to distinguish them. If you did not have it yourself, then most likely the ground wire will be a neutral wire.

The most difficult thing is to determine the ground loops in older houses with no ground. If, then there will be problems with measuring instruments and safety of household devices.

To prevent special difficulties, before installation work, you need to make sure that there is grounding at the entrance to the building in the switchboard, and then make connections according to the color coding of the wires.

If you need to find out if there is a ground loop in the wiring, then follow some tips:

  • In newly built houses, the voltage value in the phase-to-earth circuit is higher than in the phase-to-neutral circuit.
  • Voltage may appear between the neutral wire and ground due to the presence of a weak potential on the zero wire.
Checking transistors

Transistors are checked in a similar way. The innovative multi-testers are equipped with a gain measurement function. This meaning is denoted by one of the Greek letters, or by the letter "h" with an additional letter, for example, "e". This means that the value was measured for a semiconductor connected with a common emitter. To measure the gain of a transistor, there are two separate jacks for different ones. The values \u200b\u200bof field-effect transistors are determined differently, more difficult option, and cannot be determined by such a measuring device.

Capacitance measurement

The capacitor legs are inserted into special sockets, a voltage pulse is applied, and the discharge time is estimated. The potential difference across the capacitor decreases exponentially, according to which this parameter is estimated. This method is used in engineering for various purposes.

Temperature measurement

An additional function of some digital devices is temperature measurement, which is based on the action of a thermocouple. Modern electronic technology can determine the temperature by changing the resistance of a thermocouple. The voltage is also detected by the analog-to-digital converter and displayed.

To measure temperature, the controller deals with voltage. The multimeter has a special socket for connecting thermocouple wires. To measure the temperature, follow these steps:

  • Insert the thermocouple wires into the appropriate socket.
  • Place the thermocouple in the medium to be measured.
  • The display shows the temperature value.
Analog multimeter operation

This device operates with current, unlike digital devicewhich uses tension in its work. AT inductive coil the field of turns is amplified and deflects the arrow to the side. Such a device is used for:

  • Resistance and capacitance measurements.
  • Voltage measurements.
  • Determination of current strength.

The readings of all parameters are displayed on an arrow screen with a graduated scale. There is a control knob for switching measurement intervals. Just like in a digital device, there are special sockets for connecting test leads.

Ohmmeter + ammeter + voltmeter \u003d multimeter. Analog and digital multimeters. Methods for checking electronic components.

The article is dedicated to all beginners and just those for whom the principles of measuring the electrical characteristics of various components are still a mystery ...

Multimeter - a universal instrument for measurements.

Measuring voltage, current, resistance and even a simple wire break test is not complete without the use of measuring tools. Where can we go without them. Even the suitability of a battery cannot be measured, and even more so it is simply impossible to find out at least something about the state of an electronic circuit without measurements.

The voltage is measured with a voltmeter, the ammeter is measured by the current strength, the resistance is measured with an ohmmeter, but this article will focus on a multimeter, which is a universal device for measuring voltages, current and resistance.

There are two main types of multimeters on sale:.

In an analog multimeter, the measurement results are observed by the movement of the arrow (as on a clock) along the measuring scale, on which the values \u200b\u200bare signed: voltage, current, resistance. On many (especially Asian manufacturers) multimeters, the scale is not very convenient, and for the one who first took such a device in his hand, the measurement can cause some problems. The popularity of analog multimeters is due to their availability and price ($ 2-3), and the main disadvantage is some error in the measurement results. For a more accurate adjustment in analog multimeters there is a special trimming resistor, which can be manipulated to achieve a little more accuracy. However, in cases where more accurate measurements are desired, use of a digital multimeter is best.

The main difference from the analogue is that the measurement results are displayed on a special screen (in old models on LEDs, in new ones on a liquid crystal display). In addition, digital multimeters have higher accuracy and are easy to use, since you do not have to understand all the intricacies of the graduation of the measuring scale, as in the arrow versions.

A little more detail about what is responsible for what ..

Any multimeter has two leads, black and red, and from two to four sockets (there are even more on old Russian ones). The black lead is common (mass). Red is called a potential lead and is used for measurements. The general pin jack is marked as com or just (-) i.e. minus, and the pin itself at the end often has a so-called "crocodile", so that during the measurement it can be hooked onto the mass of the electronic circuit. The red lead is inserted into the socket marked with resistance or volt symbols (ft, V or +), if there are more than two sockets, then the rest are usually intended for the red lead when measuring current. Marked as A (ampere), mA (milliampere), 10A or 20A respectively ..

The multimeter switch allows you to select one multiple measurement range. For example, the simplest Chinese pointer tester:

    Direct (DCV) and alternating (ACV) voltage: 10V, 50V, 250V, 1000V.

    Current (mA): 0.5mA, 50mA, 500mA.

    Resistance (denoted by an icon that looks a bit like headphones): X1K, X100, X10, which means multiplication by a certain value, in digital multimeters it is usually indicated as standard: 200Ohm, 2kOhm, 20kOhm, 200kOhm, 2MOhm.

On digital multimeters, measurement limits are usually greater, in addition, additional functions are often added, such as audible "continuity" of diodes, checking transistor transitions, a frequency meter, measuring the capacitance of capacitors and a temperature sensor.

In order for the multimeter not to fail when measuring voltage or current, especially if their value is unknown, it is advisable to set the switch to the maximum possible measurement limit, and only if the reading is too small, to get a more accurate result, switch the multimeter to the limit below current.

Starting measurements

Testing voltage, resistance, current

It is nowhere easier to measure the voltage, if we set the constant dcv, if the variable is acv, connect the probes and see the result, if there is nothing on the screen, there is no voltage either. With resistance, it's just as simple, we touch the probes to the two ends of the one whose resistance you need to know, in the same way, in the ohmmeter mode, wires and tracks are called for an open circuit. Current measurements differ in that they must be cut into the circuit, as if it were one of the components of this very circuit.

Checking resistors

The resistor must be soldered out of the electrical circuit at least one end to be sure that no other circuit components affect the result. We connect the probes to the two ends of the resistor and compare the ohmmeter readings with the value indicated on the resistor itself. It is worth considering the tolerance value (possible deviations from the norm), i.e. if, according to the marking, the resistor is 200 kOhm with a tolerance of ± 15%, its actual resistance can be in the range of 170-230 kOhm. For more severe deviations, the resistor is considered defective.

When checking the variable resistors, we first measure the resistance between the extreme terminals (must correspond to the value of the resistor), and then connect the multimeter probe to the middle terminal, alternately with each of the extreme ones. When the axis of the variable resistor rotates, the resistance should change smoothly, from zero to its maximum value, in this case it is more convenient to use an analog multimeter watching the movement of the arrow than rapidly changing numbers on the liquid crystal screen.

Diode test

If there is a diode test function, then everything is simple, we connect the probes, the diode rings in one direction, but not in the other. If this function is not present, set the switch to 1kΩ in resistance measurement mode and check the diode. When you connect the red output of the multimeter to the anode of the diode, and the black one to the cathode, you will see its forward resistance, when connected back, the resistance will be so high that at this measurement limit you will not see anything. If the diode is broken, its resistance in any direction will be equal to zero, if it is cut off, then the resistance in either direction will be infinitely large.

Checking capacitors

It is best to use special instruments to test capacitors, but a regular analog multimeter can help. A breakdown of a capacitor is easily detected by checking the resistance between its terminals, in this case it will be zero, more difficult with increased capacitor leakage.

When connected in ohmmeter mode to the terminals of an electrolytic capacitor, observing the polarity (plus to pluses, Munus to minus), the internal circuits of the device charge the capacitor, while the arrow slowly creeps up, showing an increase in resistance. The higher the capacitor rating, the slower the arrow moves. When it practically stops, change the polarity and watch the arrow return to zero position. If something is wrong, most likely there is a leak and the capacitor is not suitable for further use. It is worth practicing, because only with a certain practice can you not be mistaken.

Checking transistors

And a couple more tips in the end

When using a pointer multimeter, place it on a horizontal surface, as reading accuracy may deteriorate in other positions. Do not forget to calibrate the device, to do this, simply close the probes between you and the variable resistor (potentiometer), so that the arrow points exactly to zero. Do not leave the multimeter on, even if there is no off position on the analog instrument on the switch. do not leave it in ohmmeter mode, as in this mode the battery charge is constantly lost, it is better to put the switch on the voltage measurement.

In general, while this is all that I wanted to say, I think that newcomers will have no questions about this, but in general there are so many subtleties in this matter that it is simply impossible to talk about everything. For the most part, this is not even taught. It comes naturally. And only with practice. So, practice, measure, test, and each time your knowledge will be stronger, and you will see the benefits of this already with the next problem. Just do not forget about safety precautions, after all, high currents and high voltages can cause trouble!

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