Electric multimeter: tester for electrical measurements
Electric Multimeter: tester for various electrical measurements
From this article you can find out what an electric multimeter is: a tester that can measure current, DC and AC voltage and resistance. Let’s consider which devices have additional functions, such as measuring the gain of a transistor, testing diodes, ringing an electrical circuit, measuring the frequency of an electrical signal, temperature, parameters of capacitors, inductance of coils.
The multimeter is used to remove a fairly wide range of indicators of electrical complexes
Electric Multimeter: tester for measuring electrical characteristics
To measure electrical parameters, universal multimeters (testers), current pliers DT 266 are often used, which are a portable compact model of the device. All multimeters have a similar design except for some distinctive features. A regular tester consists of:
- LCD display;
Modern testers combine the functions of a voltmeter, an ohmmeter, an ammeter, a frequency meter, as well as an inductance and capacitance meter
- rotary switch of measurement modes;
- three connectors for connecting probes;
- sockets for connecting a transistor;
- on/off buttons.
On the body of the digital multimeter (tester) there is a scale of designations of the measured values and their maximum values. By turning the switch, you can select one of them:
- DCV – DC voltage measurement;
- ACV – measurement of alternating voltage;
- Ω — resistance measurement;
- DCA – DC current measurement;
- HFE – measurement of transistor parameters;
- diode sign – checking or ringing diodes
Scale of notation of measured values and their maximum values
The device is equipped with several sockets for connecting red and black probes. Probes are included in the kit, but they are often elements of low quality. If they fail, you can make probes for the multimeter with your own hands, for example, from the cases of a fountain pen and the tips of a dart. To measure the values, they must be properly connected, otherwise the multimeter can be disabled. The black probe should be connected to the COM socket, and the red one is connected to the 10A connector for measuring current over 200 mA, and to the VAΩ socket when voltage, resistance, current up to 200 mA is measured, and when ringing is performed.
How to use a multimeter correctly
Before you start measuring electrical quantities, you should check the device. It must be connected to an outlet in parallel with another tester or voltmeter and check the readings. To check the accuracy of the resistance measurement, you should take a marked device and compare it with the tester’s reading. To verify the accuracy of the measurement of the amperage, it is worth taking alternate measurements of the same load with this device and an ammeter.
Using the example of the DT 832 multimeter, the operating instructions of which contain a detailed description of all manipulations with the device, we will consider the main operating modes of the device.
The resistance scale can be used for such purposes as ringing a transformer with a multimeter, determining the resistance of a resistor, identifying faulty elements, where the undervoltage, reverse resistance of diodes, and resistance of the heating element are shown.
When using a multitester, it is very important to follow all safety rules
To measure the resistance, it is necessary to set the rotary switch to the corresponding sector Ω. If the approximate value is unknown, the switch is set to the lowest value, which corresponds to 200 ohms. If the display shows “1”, it means that the resistance is greater, so you need to move to the next level. Make measurements until the correct information is obtained.
Pay attention! It should be remembered that before measuring the resistance, it is necessary to make sure that there is no power in the network. Otherwise, the device will give deliberately false values.
To measure the AC voltage, it is necessary to direct the switch to the V~ or ACV sector, which consists of two positions 200 V and 750 V. Measurements start from a larger value. If the result turned out to be small, then for a more accurate measurement it is worth switching to a low position. The black probe is connected to the COM connector, and the red one is connected to the VAΩ. When measuring this indicator, it is not necessary to observe the polarity.
To measure the DC voltage, the multimeter switch is installed in the V or DCV sector, where the scale is divided into 5 ranges. The measurement should start with the highest value of 1000 V, and gradually lower it until the correct result is obtained. If you do not follow this rule, the device may fail.
The scale of the measured values has the same values in all models of multimeters
Direct current measurement should be carried out with extreme care and accuracy. To do this, you need to set the switch to the desired DCA sector. Now it is necessary to attach the probes correctly. The black one is still inserted into the COM connector, and the red one should be set to VAΩ when the estimated current value does not exceed 200 mA. If the current strength is higher than this indicator, then the probe is set to 10A. If you mix up the positions, you can burn the multimeter.
It is necessary to start measuring the current strength with a multimeter from the maximum value of the measurement threshold, gradually lowering it until the required value is obtained.
Important! To measure the current strength, the multimeter should be connected to the circuit in series, and for resistance and voltage – in parallel.
Temperature measurement with a multimeter is performed using a thermocouple, which is connected to the device instead of probes.
To measure values with a multimeter, probes, a thermocouple or pliers are used
When working with electrical engineering, it is sometimes necessary to determine the inductance. It is quite difficult to find a tester with this function. To do this, you need to use a special prefix. As such an element for measuring inductance with a multimeter, a digital tester with a threshold of 200 mV voltage measurement accuracy is suitable.
How to ring wires with a multimeter
When it is necessary to determine the operability of equipment or the serviceability of electrical wiring, the first thing to do is to ring the cables and wires with a tester. It will immediately identify a possible break in the circuit, its resistance and the presence of a short circuit.
Useful advice! It is not necessary to use a model with this function to ring the wire. Not an expensive multimeter with minimal capabilities is suitable for this.
First you need to set the switch to the diode icon. The red probe should be installed in the connector Ω, the black – COM. Next, to check the device, it is necessary to close the ends of the measuring probes together. A characteristic signal should ring. Now you can start ringing the wire. To do this, it is necessary to touch the exposed sections of the cable or wire with measuring probes. An audible signal indicates the integrity of the wire. In this case, the resistance value or “0” will be displayed on the screen. If there is no sound signal, and the value “1” is displayed on the display, then the wire being tested is broken.
If the polarity is selected incorrectly, nothing will happen, but before the result, the display will display “-“
Next, let’s look at how to ring a multi-core cable with a multimeter. To do this, each end should be cleaned and divided into veins. Now it is necessary to check for a short circuit in each vein. Here the sound signal symbolizes the presence of a short circuit between the cores. This is especially important during high voltage operation.
Now it is necessary to check the integrity of all veins. The cores of one end of the cable are twisted together, and at the other end each is checked by the device. If the sound signal is absent at least once, the integrity of the conductor is violated.
Measuring the capacitance of a capacitor with a multimeter
The most common cause of breakdown of electronic equipment is a malfunction of the capacitors that are part of the board. To identify the weak link, it is necessary to ring each of them with a multimeter.
The breakdown of the capacitor can be easily determined using an electric multimeter
Before checking the capacitance of the capacitor with a multimeter, it is necessary to completely discharge it, otherwise it may spoil the measuring device. To discharge a low-voltage device, it is necessary to short-circuit its terminals, and for a high-voltage capacitor with a large capacity, a 5-10 kOhm resistor should be used, which is connected to the device.
A serviceable capacitor has a capacity of at least 0.25 mcfarad. Before checking the capacitance of the capacitor with a multimeter, the device should be set to the appropriate measurement mode to the required limit. If the tester is equipped with special landing sockets, insert a capacitor into them.
How to check a capacitor with a multimeter without soldering it out of the board? To do this, connect them to the measuring device and touch the capacitor terminals. The polarity should be strictly observed here. Otherwise, the device will immediately fail. The multimeter screen will display the capacitance value, which should be close to the nominal value. If this is not the case, the capacitor is faulty.
You can check the performance of the capacitor with a multimeter even without the capacitance measurement function
Important! It should be remembered that capacitor manufacturers always tick the negative contact on the device.
How to ring a capacitor with a multimeter if there is no function for measuring its capacitance? To do this, it is necessary to switch the device to the resistance measurement mode and touch the probes to the corresponding polarity of the terminals. The tester’s display will display a value that will grow. This is due to the fact that the multimeter, in contact with the capacitor, charges it. After a while, “1” will appear on the screen, which indicates the correct condition of the device.
If the number “1” appears on the screen at the beginning of the check, it means that there has been a break in the capacitor and it is already faulty. If “0” appears, a short circuit has occurred inside the device.
A more detailed course of measurements can be viewed on the video – how to check a capacitor with a multimeter.
Related article:
Multimeter: which is the best device to choose for use at home
Characteristic features of the device. Varieties of testers. How to use the device correctly. Rating of the most popular models.
How to call multimeter resistors
A resistor is an electronic element with a variable or definite value of electrical resistance. Before ringing the resistor with a multimeter, it is necessary to visually inspect it for the presence of chips and cracks on the device body. If there is no visible damage, then you should start checking the element. To do this, it is necessary to use a schematic diagram, on the basis of which measurements are carried out at control points, where the necessary values of the quantities are indicated.
The most common way to check a multimeter with a resistor is to measure the resistance, which should be close to the nominal. To do this, the tester switch is set to the appropriate position. The red probe is connected to the VΩmA connector, and the black one is connected to the COM.
A multifunctional tester is also used to check the resistors
Before ringing the resistor, it is necessary to identify the serviceable condition of its wires. They are closed among themselves. The device should display “0”. Now you can proceed to measuring the resistance of the resistor. If the display shows “1”, the resistor is faulty. If another value is displayed, it is compared with the nominal value, taking into account the tolerance. The resistor is fine if the values match.
How to check a resistor with a multimeter without soldering it out of the board? To do this, you can use the ringing mode. If the element is in good condition, a characteristic signal will sound.
The use of a multimeter in everyday life
With the help of the tester, it is possible to diagnose many elements of electrical appliances and thereby identify a malfunction.
Before ringing the TEN with a multimeter, you should find out its resistance, which will be compared with the tester’s reading. To do this, use the formula R = U2 / P, where U is the supplied voltage, P is the power, which is indicated on the device body.
A popular problem of household appliances is the failure of the heating element, which can be checked using a multimeter
To measure, set the switch to the required range for measuring resistance. Attach the multimeter probes to the housing of the household appliance and to the output contacts of the heating element in turn. If the display shows a value close to that obtained from the formula, then the heater is in good condition. A value of “0” indicates a short circuit inside the spiral, and an infinite value or “1” indicates that the spiral is broken.
The question often arises: how to ring the electric motor of a household appliance with a multimeter? Since there are several types of engines, checking the performance of the unit will be different.
Before checking the electric motor with a multimeter, it is necessary to make an external inspection of it, touch the metal surfaces with your hands.
Before checking, the device must be completely de-energized. Set the tester to the ohmmeter mode by switching to the maximum measurement range. How to work with a multimeter, the video in the article clearly displays the sequence of measurements to check the performance of the engine.
When measuring indicators, it is necessary to take into account the errors of the multimeter
Today, many lighting devices are equipped with progressive light sources, such as LEDs, which can periodically fail. It is then that an important task arises, how to check the LED with a multimeter. To do this, you need to use a tester with a ringing mode in which the performance of the diodes is checked. The polarity of the LED should be strictly observed here.
The red probe of the device is connected to the anode, and the black one to the cathode. If everything is done correctly, the working LED should start to glow. However, it should be borne in mind that when working in the ringing mode, the multimeter has a low current indicator, so the diode may not react. Here you should reduce the lighting to clearly see the glow of the diode. Also, the correct condition of the element is indicated by the displayed value on the tester’s display, which differs from 1.
Useful advice! Here you can simultaneously check the LED power with a multimeter by calculating this parameter based on the results obtained.
Digital devices have the function of fixing readings, which is convenient when checking several indicators
With the help of the tester, it is possible to identify two defects in the operation of a simple voltage and current converter. Before checking a transformer with a multimeter, it is necessary to know the conclusions of all its windings. Then, using a measuring device, ring each winding of the device in the ohmmeter mode. If 1 is displayed on the tester screen, this indicates a winding break.
To detect a short circuit, one probe of the tester should be touched to the winding terminal, the other should be connected alternately to the terminals of other windings and the housing. There should be no short circuit here.
How to check the battery capacity with a multimeter
Rechargeable batteries are used to accumulate and supply consumers with electrical energy during autonomous operation. Using a multimeter, you can check the operating voltage, operating current, internal resistance, EMF and battery leakage current. The most common question is how to check the battery charging with a multimeter.
With the help of a multitester, you can check the battery charge
To do this, it is necessary to ensure that the battery is fully charged. Further, with the help of a powerful consumer, a load is created on the battery by connecting the battery, the tester and the consumer in series. The current is measured. Periodically, it is necessary to measure the battery voltage. As soon as this value begins to decrease, the start time of battery discharge is recorded. Now the total time that has passed since the start of the test is multiplied by the load current. The resulting value corresponds to the battery capacity.
The result obtained after checking the battery with a multimeter should be compared with the passport data. If the value is lower than the nominal value, the device is not suitable for further operation.
When using many household appliances, some users are interested in how to check the capacity of the 18650 battery with a multimeter. First you need to know the nominal capacity of the element, the value of which is usually written on the case.
For ringing and troubleshooting, the multimeter has a built-in function for generating a test signal
Considering the question of how to measure the battery capacity with a multimeter, it is necessary to understand the technology of the process. The measuring device is switched to the DC measurement mode in the range of 10 MA. Next, the red probe is connected to the positive contact of the battery, and the black one is connected to the negative one. The screen should display a value that is close to the nominal value. Then the element is suitable for further work.
After checking the battery capacity with a multimeter, according to the value obtained on the device, we can talk about the further fate of the element. If the result is slightly lower than the nominal, the battery can be used for more powerful equipment, for example, for a watch, a flashlight. If the value is close to 1 A, the element will be useful to ensure the operability of the remote control.
If there is a question of how to check the battery capacity of the phone with a multimeter, it should be remembered that the tester will show only an approximate value. For a more accurate diagnosis, you should use a computer program or a special charger.
The multimeter cannot measure the battery capacity of the phone, but only the approximate value of consumption in amperes
Application of a multimeter for a car
A lot of car owners often wonder: how to check the car battery with a multimeter while the engine is running? To do this, the tester is switched to the voltage measurement mode. Observing the polarity, the measuring device is connected to the battery. If the display shows a value of 13.5-14 V, this indicates the normal operating condition of the power supply. If the value is higher than 14.2 V, it is a sign of a low charge.
Now let’s move on to the question of how to check the battery charge on a non-working engine with a multimeter. The measurement principle remains the same as when the engine is running. The normal operation of the battery should correspond to the received value, which is in the range of 12.5-13 V. If the value is lower than 12 V, this indicates that the unit is completely discharged.
One of the important parts of any car is a DMRV. How to check the flow meter with a multimeter is described below. To do this, you need to understand the design of the sensor and clearly follow the instructions.
To check the operability of the mass air flow sensor, it is not necessary to use the services of a car service. Saving money and time, you can perform a DMRV check with a multimeter. To begin with, you should know the pinout of the contact group. There is no need to remove the sensor from the installation site.
A multimeter is a necessary parting in the arsenal of a car owner, which will help save on car service services
The tester is set to the DC measurement mode up to 2 V. Checking the DMRV sensor with a multimeter is performed in a clear sequence. The red probe is touched to the yellow wire, which is responsible for feeding the incoming signal from the ECU. The black probe is connected to the green wire responsible for grounding. Turning the ignition key without starting the car, you need to look at the readings of the device.
Checking the DMRV VAZ-2114 with a multimeter was successful if the display of the device shows a value of no more than 1.02 V. The sensor does not work if a reading exceeding 1.05 V is displayed on the tester.
Pay attention! In order to check with the DMRV multimeter on VAZ 2110 how it works, it is necessary to perform all the above steps.
Before checking the camshaft sensor with a multimeter, it is necessary to turn off the ignition. Next, disconnect all the wires from the device. Switch the tester to voltage measurement mode. Connect the mass of the tester to the mass of the engine. The measurement result must correspond to the voltage characteristic of the battery terminals. If the readings are different, the device’s power supply circuit is out of order. After that, the voltage on the mass of the sensor should be measured in a similar way. It must be equal to 0.
You can check the car battery with a multimeter both when the engine is running and when the engine is not running
Now connect one wire of the multimeter to the strong terminal of the sensor, and connect the other to the input of the control system. Scroll the engine with the starter. If 0.4-5 V is displayed on the screen, the sensor is working.
How to check the detonation sensor with a multimeter? The device is set to the voltage measurement position at 200 MV. The probes are attached to the contacts. Now you should hit the body of the device with a solid object. If, depending on the impact, the voltage readings on the device increase to 40 MV, the sensor is faulty.
Next, let’s look at how to ring the ignition coil with a multimeter. First you need to make sure that the primary winding is working properly. To do this, set the device to the resistance measurement mode and connect the probes to the contacts “+” and “-“. If a value within 0.4-2 ohms is displayed on the screen, the coil is serviceable. The number 0 indicates a short circuit. If infinity is displayed, a circuit break has occurred.
The second stage of solving the question of how to check the ignition coil with a multimeter is the ringing of the secondary winding of the device. To do this, connect the multimeter probes to the output from the high voltage wire and to the “+” contact. If the coil is equipped with a plate–type core, the resistance will be 6-8 kOhm, another type – 15 kOhm.
You can check the ignition coil with a multimeter by ringing the primary and secondary windings of the device
A more detailed course of measurements can be viewed on the video “How to check the ignition coil with a multimeter”.
Checking the generator
The performance of the car’s ignition system is provided by two devices that work in pairs: a generator and a battery. Violation of the normal working condition of one of them will lead to a decrease in the operability of the entire unit.
Before checking the generator with a multimeter, you should perform an external inspection of it. Then you should start testing the relay controller, which ensures the maintenance of a constant voltage of the car. To do this, the tester is set to a constant voltage mode in the range of 50 V. With the help of probes of the corresponding polarity, the voltage at the input contacts of the generator is measured. It should be within 14-14.2 V.
The generator and the battery work in pairs, so you need to check two devices
If the fault is not detected, you should proceed to the question of how to check the diode bridge with a multimeter. To do this, it is necessary to disassemble the generator housing and check it.
If the diode bridge is in good condition, the generator rotor should be checked. To do this, it is necessary to switch the tester to the resistance measurement mode and check it on the current-removing rings of the excitation winding. The value should not be too large.
Useful advice! If a short circuit or an open circuit is detected during the measurement, you should seek help from a specialist.
The last stage is the ringing of the stator multimeter for the absence of a short circuit of the windings. The resistance on the device should be close to 1.
The latest generation of multimeters are equipped with the function of sending data to a smartphone, but the cost of such a device is quite high
How to call a diode bridge with a multimeter
In electronics, diode bridges are often used in one housing. You can find out their performance or identify damage using a regular tester.
Before ringing the diode bridge, the multimeter is set to the mode of checking the diode or ringing. The check is carried out in direct activation. The red probe is connected to the minus pin, and the black one to the pin labeled AC. This is how the threshold voltage is measured, which for silicon diodes is 400-1000 mV.
Useful advice! In order to make 100% sure that the diode bridge is working properly, the check takes place in the reverse turn-on. The black probe is connected to the minus pin, and the red one is connected to the plus pin. The value “1” should be displayed on the multimeter screen. This means that there is a large resistance in the P-N junction, and the diodes do not pass current.
All bridge diodes are checked in this way. If, during the ringing of the diodes, zero resistance is displayed on the multimeter display or the device emits a signal, this indicates a broken element inside the diode bridge. When checking in the reverse power-up, “1” will also appear on the screen. However, if a unit is displayed on the display of the device during both forward and reverse switching, this indicates a break when the diode does not conduct current.
The use of a multimeter when checking the operability or damage of a diode bridge
Before using the measuring device, it is necessary to study in detail the instructions “How to use a multimeter”, which describes in detail all possible manipulations with the tester. Strictly following the recommendations, it is possible to carry out all the necessary measurements that will not disable the device and make its operation safe.
