Rules of use of the tester (multimeter)

The tester (multimeter) is the measuring tool necessary for those whose hobby — electricity. Besides, it can often be useful in the house as allows to reveal damages at electric devices, to check the charge of the accumulator or battery and to measure the operating voltage of many electric devices.

Устройство тестера

Tester device.

For the person who for the first time faced him it is the real black box. It is not necessary to give in to the impression of a little sophisticated appearance of the tester (digits, badges, plugs for pins, etc.). The nobility is enough very little to be convinced that just to use this tool, and, above all that with its invaluable help it is possible to find breakdowns in electric devices (and to solve the related problems), beginning from the bulb and finishing difficult household devices.

Types and design

Two testers represented in the photo belong to two different types. At the left — the analog tester, at it in the window the arrow which, deviating from the zero mark, specifies the measured value on the scale is visible. On the right — the digital tester: the measured value appears on the display in the form of digits. All testers have isolated probes connected to the device by means of plugs with which conducting part touch places of measurements.

At first sight the tester can seem the difficult tool in use. In fact it is the convenient and practical device in work. From the different models which are available on sale it is better to get the simplest and cheap. More difficult devices are intended for implementation of thin measurements which will hardly interest the nonspecialist.

The measured values can be read out from the pointer indicator (analog type) or directly from the display (digital type). In the latter case reading appears obviously much more simply and quicker. All testers, besides, are equipped with two probes with the isolated handles which are connected to the device by two electrical wires by means of plugs to which the opposite ends of these wires are connected. The majority of models has the rotary switch by means of which the type of the carried-out measurement is chosen.

By means of the handle of the switch it is possible to make the choice as measurand (tension, resistance, current intensity), and measurement range for each of the above-mentioned measured characteristics. At the tester with pointer indication, depending on measurement type, it is necessary to read out value from the corresponding scale. It can be necessary to measure such sizes as tension (variable or constant), the electrical resistance and current intensity (at the alternating or constant voltage).

Possible measurements

Электрическая схема мультиметра

Multimeter circuitry.

The curve with the caused digital values is intended for removal of the different parameters (tension, resistance, current intensity) given at measurement. Setting the rotary switch to different positions, it is possible to receive different ranges of measurement. Resistance is measured in the following ranges: in ohms (Ohms), h10, h100 and h1000. To choose one of these ranges, it is necessary to establish the switch beak as appropriate. The value specified by the arrow should be increased respectively on 10, 100 or 1000. Tension (variable and constant) is measured in volts (In). And in this case on the tester different ranges of measurement (10, 50, 250, 500 V) are established. Current intensity is specified in amperes (A) and milliamperes (mA). All testers can carry out measurements of force of the direct current in amperes, only the best models can measure alternating-current force.

Strain measurement

Strain measurement allows not only to learn its size, but also to define, eat simply it or not. For example, by means of the tester it is possible to learn whether there is tension in the socket or whether the accumulator was charged. To make measurement, it is necessary to choose the measured parameter by means of the rotary switch (choose "alternating voltage") for electric devices or "constant voltage" for accumulators, batteries, etc. and the measurement range, suitable for this measurement. At touch by probes to elements between which there is tension (contact openings of the socket, accumulator plugs, etc.) the arrow deviates the zero mark and specifies the value corresponding to tension size on the scale. Well, and if the tester digital, on the display appears the number designating tension size in volts (or volt shares).

Measurement of resistance

Measurement of resistance is very important when it is necessary to check whether there was no break in the electric circuit, the device of some devices (the iron, the electric lamp, etc.) represents electric circuit which "begins" and "comes to an end" with plugs of the network fork. If the device does not work, it can be useful to check whether there is no gap in this chain. At measurement of resistance at first, as well as at other measurements, choose range as appropriate having installed the switch on the tester. Then probes concern points between which it is necessary to measure resistance. If the value of resistance indicates "infinity", it speaks about break in the chain and need of repair.

At installation of the switch on the ring-up mode on the sound signal you can make sure whether incandescence thread in the lamp fused, whether there is no break in the internal winding or whether the wire departed from contact in the socket. Besides, such technique gives the chance to find conclusions of each winding in the inductance coil or to check whether the switch works and also to check operability of the safety lock.

Prevention: before undertaking measurement of resistance, it is necessary to make sure precisely that the chain is deenergized!

Measurement of current intensity

Проверка тока утечки

Check of the leakage current.

Measurement of current intensity — more "distinguished" use of the tester. It should be made with care. Therefore for bigger safety it is better to entrust this operation to the professional. The matter is that the similar measurement becomes in the chain which is energized (that is when in it there is current), and demands special knowledge and technical skills. In other words, it is about "consecutive" inclusion of the tester in the chain of the working device; the measurement is made when current passes through it and, respectively, through the tester. Naturally, it is necessary to install previously the tester switch on the corresponding type of measurement (amperes for variable or milliamperes for the direct current).

Sequence of measurements. Expose the type of measurement which you should make by means of the switch. Also the necessary range of measurement is at the same time exposed.

Measurement range. This maximum value of the scale within which measurements are taken by the analog tester and which changes for receiving more exact measurements. If you measure tension in 4 V on the 1000-voltaic scale, the arrow deviation from zero risks will be so insignificant that will begin almost impossible to read the instrument. But if by means of the switch to choose smaller range, 10 V, the arrow will make the noticeable deviation from zero risks that much more exact removal of the indication will allow. Thus, any value on the scale can be correlated to measurement range. Insert pins of probes into the corresponding connectors that the tester could be connected to the chain in which you are going to perform measurements. For check of whether the bulb fused, touch with probes the thread and contact part of its socle and measure resistance.

If the device shows infinite value, it means that the bulb fused. The discharge of the battery is easily checked by means of strain measurement between its poles. If it is explicit below rated, it indicates that it is discharged. Choose the scale of strain measurement of alternating current (measurement range not less than 250 volts), connect device probes to the socket and be convinced that the arrow shows 220 volts.

During the work with high tension be accurate, do not touch metal parts of probes!

Installation of the arrow on the zero mark

At the tester with the analog scale of the shooter at rest can match the zero mark not absolutely. You can set it to zero, rotating the screw located under the scale regulating the arrow spin axis. To check whether the tester correctly works and whether the battery sat down in it, install the switch on measurement of resistance and close probes short. The arrow has to deviate towards the zero mark in the ohmic scale.

Battery for the tester

Схема измерения общего тока

Scheme of measurement of the general current.

In each tester there is the battery developing current and necessary for measurement of resistance. It should be replaced periodically: in spite of the fact that measurement of resistance consumes not enough energy, eventually the element loses the charge. The tester — the thin device which cannot be subjected to blows and which should be preserved against hit of water in it.

How to use the multimeter? This question is often set at the forum therefore this short guide was written. For the example the most widespread and cheap Chinese multimeter was taken for 150 rubles. Accuracy should not be expected from such priborchik, but it quite copes with the duties.

I will begin with interpretation of the switch. DCV – measurement of constant voltage. ACV - measurement of alternating voltage. DCA – measurement of the direct current. HFE – measurement of transistor parameters. temp – temperature measurement by means of the special sensor. Measurement of resistance – the sign Ohm, at me is not present it on the keyboard. On normal devices there is the sign HZ – measurement of frequency, the EXPERT - alternating-current measurement, memory of results, etc. We measure constant voltage, we check the Krone battery. For this purpose we choose the corresponding limit of measurement as the switch, 20 volts in this case quite approach. On the future if tension (current, resistance) is unknown even approximately, we begin measurement with the maximum size, otherwise the device can fail.

On the priborchik there is the red and black wire. Red, as well as always in electrical equipment, it is considered to be plus. We include it in the positive connector of the multimeter which is not difficult for finding if to read texts about slots of the device. If to mix polarity of the measured tension, nothing terrible will occur, just before size on the display there will be minus. Here it, the Chinese accuracy, in dead Krone nearly 10 volts were found.

Now we will take measurement of alternating voltage of the household power supply network. We choose the necessary position of the switch and we measure. Always it is necessary to show consideration for this procedure, at incorrect situation the device will fail. It is excessive to say that before such experiences it is necessary to be convinced of operability of isolation of wires and probes of the tester. And now in more detail about the device.... The MULTIMETER of DT-830B consists of such elements as - the display / to - the multiple switch - slots for connection of probes - the panel for check of transistors - the back cover (it will be necessary for replacement of the battery of the device, the "Krone" 9 element of volts).

Provisions of the switch are separated into sectors: OFF/ON - the switch of the power supply of the device, DCV - strain measurement of the direct current (voltmeter), ACV - alternating-current strain measurement (voltmeter), hFe - the sector of inclusion of measurement of transistors, 1.5v-9v - check of batteries. For convenient studying of the device click it. DCA - measurement of the direct current (ampermeter). 10A - the sector of the ampermeter for measurement of great values of the direct current (according to the instruction measurements are taken within several seconds). The diode - the sector for check of diodes. Ohm - the sector of measurement of resistance. The sector DCV which on this device is separated into 5 ranges. Measurements from 0 to 500 volts are taken. Direct current voltage of big size to us will meet only at repair of the TV. At the big tension it is necessary to work with this device extremely carefully.

At inclusion in  the provision "500 volts" on the screen in the left upper corner the warning of HV that the most top level of measurement is included lights up and at emergence of great values it is necessary to be extremely attentive. Usually strain measurement is conducted by switching of big provisions of range on smaller if you do not know the size of the measured tension. For example, before strain measurement on the rechargeable battery of the cell phone or the car on which the maximum voltage of 3 or 12 volts is written we put safely the sector in position "20" of volts. If we put on smaller, for example on "2000" millivolts, the device can fail. If we put on big, instrument readings will be less exact. When you do not know the size of the measured tension (of course, within household electric equipment where it does not exceed device sizes), then expose on upper situation, "500 volts", and do measurement.

In general, roughly to measure, with an accuracy of one volt, it is possible on the provision "500 volts". If big accuracy is required, switch to the lower situation, only that the size of the measured tension did not exceed value on position of the switch of the device. This device is convenient in measurement of direct current voltage that it does not demand obligatory respect for polarity. If the polarity of probes ("+" - red, "-" - black) does not match polarity of the measured tension, then in the left part of the screen there will be the sign "-", and size will correspond to measured.

The sector of ACV has on this kind of the device 2 provisions - "500" and "200" volts. Carefully address with measurements of 220-380 volts. The order of measurements and installation of provisions is similar to the sector DCV.

Is the milliammeter of the direct current and it is applied to measurement of small currents, generally in radio-electronic schemes. It is not useful to us yet. In order to avoid breakdown of the device do not put the switch on this sector. If you forget and you will begin to measure tension, then the device will fail.

In this regard it is necessary to tell the cautionary story. Being the curious child and already aware how to ring out the electric circuit, for example filament of the lamp or the wire on break, by means of the device, I did not distinguish that such tension and current. I do not remember what happened to the device which I had, but it was required "to ring out" "tester" something on break. Asked for the friend. Vasya took from the father. Good pointer USAn C - 2..., I do not remember already what, Vasya gave me. Having measured that it was necessary, I put the device aside and forgot about it. And remembered when saw what on the socket in the wall is written to 220 V 6 A. Whether I wanted to be convinced of instrument accuracy, whether in compliance written on the socket, well, tension I measured, it corresponded.

Of course, the switch stood on strain measurement as it is necessary. Now, without thinking twice, I put the switch in position 10 A of measurement of current and I insert probes into mysterious holes in the wall. I do not remember such explosion for all the life. Broke off the device on the turned black splinters, the Black had the person as in the dark, ears were stuffed up for half an hour, well at home there was nobody, so would receive according to "the full program". And so, before trying to do something, at the slightest suspicion on presence of tension, it is necessary to know what is current, tension, resistance.

We go further. There is still the provision 10 A of measurement of the direct current (ampermeter). Measurements are performed with shift of the wire from the second slot to the slot 10 A. If you need to measure current of any electric device, it is possible to use the ampermeter, but besides carefully. To instructions on the device it is written that it is necessary to perform measurements of current several seconds, but I would not recommend to use this opportunity once again.

Sector of measurement of resistance (ohmmeter). It is separated into situation from 200 Ohms to 2 megohms (2 000 000 Ohms). It is possible to measure resistance from 1 Ohms to 2 megohms with the following nuances. First, the Chinese multimeter is not precise instrument and the error of its indications is quite big. Secondly, unpredictable big sensitivity at precise measurements. In this regard, at short circuit of probes among themselves the device indicates resistance of the chain which should not be neglected, and to consider it for wire resistance on probes, i.e. at measurement of small resistance from result it is necessary to take away the value received at short circuit of probes.

For example, we measure lamp resistance. Since the lamp has small resistance, we put the device in position of 200 Ohms. At first we will close probes among themselves. My device showed 0.9 Ohms. We will take away it after measurement of resistance necessary to us. We measure on the lamp, we receive 70.8 - 0,9 = 69.9 Ohms. Consider that indications are approximate, but in our cases with electrical household appliances of it it is enough. Work up the range of the sector does not represent anything difficult. If at you on the screen unit is shown at the left, then resistance is more, than the established position of the switch and if unit on the screen at position of the switch 2000 kOhm, then it is possible to consider the chain torn off. At emergence of digits the certain resistance in the chain has presence.

Replacement of the battery. As soon as you notice failure on the display, for example digits vanish or indications do not correspond to approximate values, so came it is time to replace the battery at the device.

Sector Diode. Shows voltage drop on transition, from 400 to 700 MV, in forward direction on the operational diode and infinity, i.e. unit at the left in the opposite direction. On faulty, in both directions: 1. Close to zero - value of breakdown. 2. Close to infinity - break.

Sector of hFE. For measurement of transistors there is the panelka with the instruction in what slot what leg of the transistor to place. Transistors of both n - р - n and р - п - р provodimost are checked for breakdown, break. Shows the static transfer ratio of current (only silicon - KT).

COMMENTS
  1. Ilya

    Read, saw learned to work with the tester) Thanks.

    To answer
  2. Volodya

    Article is very useful, for the end understood how to use the tester.

    To answer
  3. Vitaly

    Everything is clear Thanks to the author.

    To answer
  4. Stas

    Read, saw learned to work with the tester) Thanks!

    To answer
  5. Vadim

    Excellent article. Itself faced recently need to use the tester, available was only analog (the late father was the excellent electrician, and I was never interested in it). Thanks to this article got a lot of necessary knowledge which were useful to me today, and will be useful in the future. Thanks to the author!!

    To answer
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