Digital and analog multimeter: parameters and differences, selection criteria and the best manufacturers

The tester is a multifunctional device designed to measure all kinds of radio and electrical quantities. Its other name is a multimeter. The word multimeter comes from the English multimeter (functional meter) and is a complex electrical measuring device.

With the help of the tester, you can easily determine the voltage and current strength, the resistance of the conductors, find out the parameters of diodes and transistors, and check the integrity of the cable. Using the multimeter in conjunction with other radio measuring devices, you can repair any type of radio devices, electrical wiring and its parts.

Types of devices and characteristics

Multimeters are used by both professionals and novice radio amateurs. Marketplaces offer testers that differ in capabilities and cost. Having found out what their differences are, which functions are paramount, it will be easy to choose a device with an acceptable price for yourself. Such a device will be useful both in household and professional activities.

By its functionality and principle of operation manufactured devices are divided into:

• analog multimeters;
• digital multimeters;
• combined.

By the nature of the measurement, they are highly specialized and multifunctional. Additionally, testers are characterized by the error value, measurement range, and the presence of protection.

When working with your multimeter, it is important to understand the icons shown on it. Such icons are the following generally accepted designations:

• ACA or A ~ - AC voltage current.
• ACV or V ~ - alternating voltage.
• DCA or A - constant voltage current.
• DCV or V - constant voltage.
• А, mA - current value in amperes or milliamperes.
• V, mA - voltage value in volts or millivolts.
• Ohm, kOhm, MOhm - resistance value in ohms, kilo-ohms and mega-ohms.
• hFE is the current gain of the transistor.
• o)) - short circuit dialing.
• Cx - capacity.
• COM - negative socket for connecting the probe.
• V / Ω is the positive socket for connecting the probe.
• C0 - thermocouple connection point (temperature measurement).
• On / Off - turn on or off the device.

Possibilities of a pointer device

The very first measuring instruments were supplied with a pointer device. It is an electromechanical head. Structurally, it is made in the form of a frame, which is located in a magnetic field. An electrical signal is applied to this head through various resistances. Depending on the current strength, the arrow in the frame deflects, setting in a certain position. The range of deflection of the arrow is graduated, according to these values ​​and the required value is calculated.

The technical capabilities of an analog tester are largely determined by the sensitivity of the magnetoelectric measuring device. The main advantage of this type of device is inertia and immunity to interference during the measurement of DC voltage and resistance values. For example, when calculating a DC voltage with ripple, the tester will ignore it and display the average value. You can expand the measurement range by using additional resistances or a shunt.

Pointers are ideal for displaying signal dynamics. An analog multimeter instantly shows the change in the signal. At the same time, such a device has a large measurement error in high-resistance circuits and some difficulty in interpreting the measurement results. With each measurement, it is necessary to analyze the position of the arrow on a certain range corresponding to the type of current and the signal being tested.

Differences of a digital device

The main feature of a digital multimeter is the presence of a liquid crystal screen on which the measured value is clearly displayed. The principle of operation of the device is based on the comparison of the measured signal with the reference one; for this, an analog-to-digital converter (ADC) built into the device is used.

Digital multimeters are available in both mobile and stationary form. Power supply of mobile devices is carried out using portable batteries (for example, a 9 V crown battery). Stationary testers are connected to a 220 V AC network.

One of the characteristics of the device is its capacity. It indicates how accurately the device can measure. For example, a bit depth of 3.5 means that the device screen has four full digits in the range from 0 to 9 and one with a limitation. The accuracy of such a tester is one percent. Bit depth with a value of 3.5 is most common in portable devices, but at the same time digital multimeters with a value of more than five are produced, their accuracy is more than 0.1%.

Typical inaccuracy of digital meters when measuring constant values ​​lies in the limit of 0.2%, when measuring variable values ​​- 0.3%. It should be noted here that with an increase in the signal frequency measurement uncertainty increases.

The input impedance does not depend on the measurement range and is about 11 MΩ, the internal capacitance is 100 pF, the drop in the potential difference when determining the current is about 0.2 V. Power consumption while measuring DC voltages and currents is 0.018 W and 0.063 W when measuring resistance, AC voltage and current. The digital device allows measurements at battery voltage up to 7.5 V.

The measurement quality is determined not by the bit depth, but by the type of the analog-to-digital converter. It also depends on the accuracy of the calibration and the class of radio components used.

Multimeter selection criteria

The number of manufactured devices is so great that everyone can choose a device for himself, fully satisfying the requirements imposed on it, both in terms of characteristics and a set functions. The price of a tester is determined by its functionality, workmanship and measurement accuracy.

Additional functionality of testers

In addition to the standard set of values, testers allow measuring capacitance, inductance, temperature and frequency, calculating parameters of pulse signals, check the circuit for integrity by giving a sound signal or by a sharp deviation arrows. Often, a multimeter has the ability to check the parameters of semiconductor devices, it contains a built-in meander-type generator.

Device, liquid crystal with special logic elements, it can replace the simplest oscilloscope, displaying the waveform and its characteristics on the screen. A number of multimeters have interfaces for interfacing with a computer. It is a Com port for portable devices and a GPIB port for fixed devices. Such ports are necessary when the device has the ability to store measurement results for further processing.

Main design features

In their constructive form, testers are conservative and are produced in a rectangular shape. In good devices, the body is made of durable plastic with a waterproof coating. The differences are in the number of screens, types of controls (buttons, dial), dimensions of the device.

Multimeters equipped with two information screens are more informative and make it possible to make a qualitative assessment of the measured value. Often one of the screens is installed with a liquid crystal, and the other - with a pointer or LED. Because digital testers use accurate but slow analog-to-digital converters, the information on the scoreboard cannot be updated faster than once every four seconds.

Used in conjunction with an arrow or LED screen, it is possible to evaluate changes in dynamics with high accuracy. The LED indication is made in the form of a bar, the display accuracy is low, but the update rate reaches more than 15-20 times per second.

The use of devices with two digital screens allows you to see two parameters at once during measurement, for example, during voltage measurement immediately measure the current. If the screen is graphic, i.e. can visualize the waveform, such a device can easily replace a simple oscilloscope. The use of the screen backlight solves the problem of taking measurements in low light.

Protection and electrical probes

An important parameter is the ability of the multimeter to protect its electronic circuits in the event of emergency situations. For example, voltage surges, connection of the wrong measurement mode, incorrectly set measurement range.

Protection is carried out both electronic and electromechanical type. Electronic protection uses the semiconductor properties of the elements and has undeniable advantages (quick response, reliability, self-healing capability). The simplest protection is a fuse.

The devices are also characterized by the degree of electrical safety. In accordance with the international classification, measuring instruments are divided into four categories of work:

• with low-voltage circuits of electronic components;
• with local power circuits;
• with power distribution circuits in buildings;
• with distribution circuits outside buildings.

When purchasing a multimeter, you should pay attention to the quality of the test leads included with the device. The cords for the probes should be as flexible as possible, but at the same time made of thick wire with good insulation. Mounting with probes and plugs is made using additional rubber bushings designed to increase protection.

A thermocouple is also supplied with the functional testers. It consists of different types of conductors, pointwise connected to each other. Its purpose is to measure temperature. At the moment when the temperature changes at one of these contacts, a certain potential is created. Voltage measured by tester and using the ADC is converted to a temperature value.

There are also multimeters of a special type, they are explosion-proof and designed for use in hazardous conditions (in mines, oil stations, etc.) ). These multimeters have a special protective shell and case.

Measurement steps

In order to take measurements, the multimeter is connected using a set of wires to the measured object. One side of the wire is fixed into the plug, and a contact probe is put on the other side of the wire. The measurement procedure consists of the following steps:

1. Switch on the device.
2. Insert the cable plugs into the corresponding sockets on the instrument panel.
3. Select the type of measurement and range (not necessary if the tester has an automatic selection function).
4. Touch the measuring probes to the measuring points.
5. Take readings from the device screen.

Choosing a brand

Most of the devices sold are assembled using high-quality element base. But the assembly of the body parts and the installation of the board inside are of rather poor quality. Gaps in the case, poor quality of the input and output connectors, weak adjoining elements affect the service life and accuracy of the instrument readings. With the best side recommended ourselves the following trademarks:

• Mastech.
• Fluke.
• CEM.
• APPA.
• UNI-T.
• Elitech.

When choosing, you will need to evaluate the area of ​​use of the multimeter. For professional work and specialized measurements, it is better to choose a high-precision instrument. For home use, it is more convenient to purchase a digital multimeter. You can choose the price, appearance photo, characteristics and features by visiting the manufacturer's website of the device you like.

Since the appliance is powered by low voltage, it is considered safe for human health. But when using the device, it must be borne in mind that the object of measurement may pose a danger, therefore, the requirements for electrical safety must be observed.

Digital multimeter