The life of a modern person is surrounded by consumers of alternating (household appliances, power tools) and direct (cars) current. All electrical devices are assembled according to the compiled electrical circuits, the failure of the components of which leads to breakdowns of complex mechanisms. A home craftsman, armed with special equipment and the ability to understand the intricacies of electrical wires, can not only find the reason for the loss of efficiency of a wall-mounted plasma or an automatic washing machine, but also return the former colors to the TV screen, and delight the hostess with the buzzing of an indispensable assistant. A multifunctional multimeter is a must have for every DIYer, so it's important to know how to use it properly.

What is a multimeter

A multimeter is a device that measures the parameters of an electric current. Moreover, the tester - another name for the device - combines the functions of measuring instruments that determine the current strength, mains voltage and conductor resistance. Using a multimeter, they look for breaks in electrical networks, check the performance of electronic components: diodes, capacitors, triodes and other elements.

Lightweight, compact, easy-to-use tester is an indispensable helper for a home craftsman who will help to quickly and accurately determine the cause of malfunctions in the electrical circuits of household appliances, cars, home electrical wiring, power tools.

Scheme of operation of an analog tester and a digital multimeter

At first, multimeters were analog (pointer) and were called testers. Their package necessarily includes two wires with probes, which close the sections of electrical wiring, electronic components, contacts. The result of the measurements was determined by the position of the arrow on one of the scales: separately for voltage, own for current strength, individually for resistance.

Often the scales are made in different colors to improve visual perception. The main components of an analog multimeter: a permanent magnet, a moving induction coil, an arrow connected to it and a counteraction spring.

The main mechanism in the analog tester is the pointer head, which is a rather sensitive electromechanical device made in the form of a miniature coil suspended on springs. The current, passing through the turns of a coil placed in a magnetic field, turns it at a certain angle, thereby deflecting the arrow - fixed on it - and, overcoming the resistance of the spring, sets it in a specific position. This position of the arrow on the marked scale in the form of an arc is the measured value of the desired parameter.

The force with which the spring opposes the driving force of magnetic induction is directly proportional to the strength of the current passing through the inductive coil. Therefore, the scale of the ammeter and voltmeter in the pointer tester has a linear gradation.

It is clear that the accuracy of such a tester depends on several factors: position in space, mechanical impact (for example, hand trembling), ambient temperature. The analog multimeter provides for the presence of a special control device that helps to bring the arrow to zero before starting measurements.

The pointer device in the device is simple.

Its design consists of a set of carefully selected high-precision resistor shunts of various ratings, several diodes, a microammeter, and its own power supply used to measure resistances.

A digital multimeter is much more complex and consists of a set of integrated circuits specially designed for a particular measurement. The circuit diagram of a digital meter is 100% dependent on the type of components used (diodes, transistors, resistors and other semiconductor elements), electrically interconnected on a common semiconductor base (substrate), therefore, to explain the principle of operation of the device, it is much more convenient to use a block diagram that is the same for all testers of this type.

In terms of cost, a digital meter is not much more expensive than a pointer analogue, because mass production of microelectronic chips has long been established, so their cost is low. The convenience of using a digital multimeter lies in its advantages:

• accuracy;
• visibility (numbers are perceived visually more familiar than the position of the arrow on a finely graduated scale);
• automatic selection of the measuring range (volts, amperes or ohms).

Purpose of the device

Compact, pocket-type multimeters are used to measure the characteristics of electric current. But the measurement area of ​​digital analogues is much wider. They can measure the capacitance of capacitors, inductance parameters, current frequency, heating temperature of conductors. You can define the range of parameter change, the percentage of measured values ​​of the same type. The only function that is not available for them is the display of the measurement dynamics. But the arrow tester easily demonstrates the intensity of changes in the speed of the arrow (instantaneous, gradual, very slow). Analog multimeters can also be endowed with additional functions, but then the arrow testers will become bulky, heavy, inconvenient to use.

Application area

At home, a multimeter checks, as a rule, the absence or presence of current in the supply wires. In other words, the fact of a break in a cable or conductors, as well as the state of contacts in electrical circuits, is being investigated.

In these cases, the instrument switches to the ohmmeter function. More experienced users can measure the voltage, frequency and current in the mains. Advanced owners of a multifunctional device check the performance of:

• electronic components in microchips of many types of household appliances - televisions, computers, washing machines and other home electrical devices;
• power tools;
• on-board network of cars;
• other electrical machines.

More recently, the tester was only in the arsenal of electricians and radio amateurs, but today it is owned by millions of users due to the ease of operation control, low cost, compactness, and the presence of many objects for measuring DC and AC parameters in our everyday reality.

Video: how to use a multimeter. Application in everyday life and auto repair

Varieties of multimeters

It is important to know that multimeters with different sensitivity ranges are used for different purposes. It is this most important parameter that determines the scope of use of each particular model. A multimeter that measures the voltage of cans in a car battery will not be able to measure the low voltage voltage of current sources, since their values ​​are expressed in millivolts. At home, fuses, sockets, incandescent lamps, heating elements, integrated circuits, transistors, automotive electronics are measured with a multimeter. All these measurements are easily handled by a digital multimeter, which is most popular among home craftsmen.

The very name of the multimeter - most accurately indicates the purpose of this multifunctional device. There are so many varieties of testers that anyone can purchase a model that meets their requirements for this device. And requests can be to the design, the range of measured values, the set of functions. Today's multimeter, in addition to measuring capabilities, can be endowed with the capabilities of various calculations and plotting a graphical representation of signals. Enough has already been said about digital and analog models. Consider other types of multimeters.

Clamp meters

It is known from school physics that a voltmeter is connected in parallel to a circuit, and an ammeter is connected in series. In order to create a gap in a high-voltage circuit to measure the current strength, clamps were invented. The first versions of electric clamps were presented in the form of a transformer, in the secondary winding of which an ammeter was connected. The readings of such a device had to be recalculated, so when measuring the current strength, the influence of the transformation ratio was not taken into account. Such clamps could only measure alternating current, they do not work with direct current. In modern current meters, instead of an ammeter, there is a Hall sensor, which is able to determine and record the presence and strength of the field for both alternating current and direct current.

There are two types of measuring clamps: professional ones for measuring networks with voltages above 1000 V and household ones - voltages less than 1000 V. The design of devices of this type is constantly being improved today, with their help such complex tasks are solved:

1. Measurement of the current strength in any section of the network that is energized.
2. Determination of the actual power consumption of any electrical device included in the network.
3. Measurement of the actual load in the electrical network of a house or a separate apartment at this time.
4. Detection of illegal connections to the power grid.
5. Checking household appliances for insulation breakdown and current leakage to the case.

Video: how to use the multimeter and current clamp DuMa8819

Photo Gallery: The Best Digital Testers of 2018

The most accurate budget tester The best price The most compact tester
Best Automated Tester Most Reliable Multimeter Best Auto Electrician Multimeter Best Value for Money Most Versatile Tester

Table: rating of models of digital testers in 2018

Instructions for use

To an unprepared person, it may seem difficult to manage this device. Buttons, switches, names in English and other things that are not very clear. But in fact, there is nothing tricky if you understand the principle of measuring various parameters.

The two main points of the rules that you need to remember first of all:
to what contacts it is necessary to connect the measuring probes correctly;
in which position the switch is set in order to correctly measure various quantities.

Introduction to multimeter language

Almost all multimeter models are made in China, so the names on them are written in English.

Abbreviations are applied in Latin, which denote:

1. ON / OFF - (eng. off switch) enable / disable the multimeter.
2. DCV = DC Voltage - (eng. Direct Current Voltage) - constant voltage.
3. ACV - AC Voltage - (Eng. Alternating Current Voltage) - alternating voltage.
4. DCA - (eng. Direct Current Amperage) - direct current strength in amperes.
5. ACA - (Eng. Altenating Current Amperage) - AC power in amperes.
6. ᘯ - resistance measurement.

Voltage measurement with a DT830 multimeter

Preparing the multimeter to start measuring the magnitude of the alternating voltage:

If a much smaller figure than 700 appears on the display, and zero is in front of it, then the switch should be moved to a lower voltage value - 200.

When measuring DC voltage, the wires with the probes remain in their sockets, and scroll the switch to the DCV area. The order of measurements is the same: start with the largest modes and gradually switch to the desired level. Important note: when measuring DC voltage, put a red probe on the positive contact, and a black wire on the negative contact. However, if the polarity is incorrect, the display will show a value with a minus sign.

Video: how to measure the voltage in a 220 volt outlet for beginners

Measuring current with a multimeter DT830B

This type of instrument can only measure direct current. Sequencing:

If the device shows a small value, then rearrange the red wire to the VᘯmA connector.

AC current greater than 10 amperes is measured using electrical clamp meters. Multimeters are simply not designed for such parameters and can simply burn out.

Video: how to measure the current in a flashlight

Resistance measurement

To measure resistance:

Video: multimeter resistance measurement

ringing

This technique is used to find out if there is an open in the circuit or if it is not damaged. For ringing, the switch is placed in the diode test position.

Checking capacitors, diodes, transistors

The purpose of the event is to determine the presence of resistance, in the same way as the continuity of conductors. The procedure is as follows:

• the black wire is inserted into the COM connector;
• red tip from the probe - into the VᘯmA connector;
• a black probe is placed on the cathode of the diode (sign -);
• the red probe closes the anode (+ sign).

The multimeter display will show numbers indicating the forward resistance of the diode. When changing the polarity (the probes are swapped), the number one should be displayed on the screen (the diode is working). If the unit appears when measuring direct resistance, the diode has burned out.

Typical malfunctions of digital multimeters and their causes

First of all, you should check the performance of the battery. If necessary, replace the CROWN. Do not leave the probe in the “10A” socket after the end of the measurements! A short circuit will burn out the circuit board tracks under the switch. It's not recoverable!

Table: Common DMM Problems

How to work with a multimeter is described in detail in this video.

Video: how to use a multimeter