A multimeter is one of the inexpensive measuring instruments that is used by both professionals and amateurs who repair home wiring and electrical appliances. Without it, any electrician feels like he has no hands. Previously, three different instruments were required to measure voltage, current, and resistance. Now all this can be measured using one universal device. Using a digital multimeter is very easy.
The main two rules to remember:
- ⚡ where to connect the measuring probes correctly
- ⚡ in what position should the switch be set to measure different quantities?
Multimeter appearance and connectors
On the front of the tester, all the inscriptions are made in English, and even using abbreviations.
What do these inscriptions mean:
- OFF - the device is turned off (to prevent the device batteries from running out, set the switch to this position after measurements)
- ACV - measurement of variable U
- DCV - constant U measurement
- DCA - DC current measurement
- Ω - resistance measurement
- hFE - measurement of transistor characteristics
- diode icon - continuity test or diode test
Switching modes occurs using the central rotary switch. When you first start using your digital multimeter, it is recommended that you immediately mark the pointer mark on the switch with contrasting paint. For example like this: 
Most device failures are due to the incorrect choice of switch position.
Power is supplied from a Krona battery. By the way, by looking at the connector for connecting the crown, you can indirectly judge whether the tester was assembled in a factory or somewhere in Chinese “cooperatives”. With high-quality assembly, connection occurs through special connectors designed for the crown. Lesser quality options use regular springs.
The multimeter has several connectors for connecting probes and only two probes. Therefore, it is important to correctly connect the probes to measure certain quantities, otherwise you can easily burn the device.
The probes are usually of different colors - red and black. The black probe is connected to the connector labeled COM (translated as “common”). Red probe into the other two connectors. The 10ADC connector is used when it is necessary to measure current from 200mA to 10A. The VΩmA connector is used for all other measurements - voltage, current up to 200mA, resistance, continuity. 
The main criticism is caused by the factory probes that come with the device. Almost every second owner of a multimeter recommends replacing them with better ones. However, their cost can be comparable to the cost of the tester itself. As a last resort, they can be improved by strengthening the bends of the wires and insulating the tips of the probes. 
If you want high-quality silicone probes with a bunch of tips, then you can order them with free shipping on AliExpress. 
Previously, pointer testers were also widely used. Some electricians even prefer them, considering them more reliable. However, due to the large error of the measurement scale, it is less convenient for ordinary consumers to use them. In addition, when working with a dial multimeter, it is imperative to guess the polarity of the contacts. For digital ones, if they are connected to the poles incorrectly, the readings will simply be displayed with a minus sign. This is normal operation and will not damage the multimeter. 
Basic Multimeter Operations
Voltage measurement
How to use a digital multimeter to measure voltage? To do this, set the switch on the multimeter to the appropriate position. If this is the voltage in the outlet at home (alternating voltage), then flip the switch to the ACV position. Insert the probes into the COM and VΩmA connectors. 
First of all, check that the connectors are connected correctly. If one of them is mistakenly installed in contact 10ADC, a short circuit will occur when measuring voltage.
Start measuring from the maximum value on the device - 750V. The polarity of the probes does not play any role at all. It is not necessary to touch the zero with a black probe, and the phase with a red one. If a much lower value is displayed on the screen, and the number “0” appears in front of it, this means that for a more accurate measurement, you can switch to another mode, with a smaller voltage level scale that your multimeter allows you to measure.
When measuring DC voltage (for example, electrical wiring in a car), switch to DCV mode. 
And you also start measuring from the largest scale, gradually lowering the measurement levels. To measure voltage, you need to connect the probes in parallel to the circuit being measured, while using your fingers to hold only the insulated part of the probe so as not to get under voltage yourself. If the display shows a voltage value with a minus sign, this means that you have reversed the polarity.
ATTENTION: when measuring voltage, be sure to check that the multimeter scale is set correctly. If you start measuring voltage with the DCA switch in the on position, i.e., measuring current, you can easily create a short circuit right in your own hands!
Some experienced electricians recommend holding both probes in one hand when measuring the voltage in an outlet. If the probes are poorly insulated and breakdown, this will allow you to protect yourself to some extent from electric shock.
The multimeter operates on a battery (a 9-volt crown is used). If the battery starts to run low, the multimeter starts to lie shamelessly. In the outlet, instead of 220V, it may seem like 300 or 100 Volts. Therefore, if the device readings begin to surprise you, first check the power supply. An indirect sign of battery discharge can be chaotic changes in the readings on the display, even when the probes are not connected to the object being measured.
Current measurement
The device can only measure direct current. The switch must be in the – DCA position. 
Be careful! When measuring current, if you do not know approximately what limits the current will be, it is better to start measuring by inserting the probe into the 10ADC connector, otherwise measuring a current of more than 200mA at the VΩmA connector can easily burn the internal fuse.
Here, probes, unlike voltage measurements, must be connected in series with the object being measured. That is, you will have to break the circuit and then connect the probes into the resulting gap. This can be done in any convenient place (at the beginning, middle, end of the chain). 
In order not to constantly hold the probes with your hands, you can use alligator clips for connection. 
Know that if, when measuring current, you mistakenly set the switch to ACV mode (voltage measurement), then most likely nothing bad will happen to the device. But if it’s the other way around, the multimeter will fail.
Resistance measurement
To measure resistance, set the switch to position - Ω. 
Choose the desired resistance value or start again with the largest one. If you are measuring resistance on some operating device or wire, it is recommended to turn off the power from it (even from the battery). This way the measurement data will be more accurate. If during measurement the value “1, OL” appears on the display, this means that the device is signaling an overload and the switch needs to be set to a larger measurement range. If “0” is displayed, then on the contrary, reduce the measurement scale.
Most often, a multimeter in resistance mode is used during repair work, to check the functionality of household appliances, the serviceability of the windings, and the absence of a short circuit in the circuit.
When measuring resistance, do not touch the bare parts of the probes with your fingers - this will affect the accuracy of the measurements.
Calling
Another operating mode of the tester that is often used is dialing.
What is it for? For example, in order to find an open circuit, or vice versa - to make sure that the circuit is not damaged (checking the integrity of the fuse). The level of resistance is no longer important here; it is important to understand what is wrong with the circuit itself - whether it is intact or not.
It should be noted that there is no sound signal on the DT830B.
For other brands, as a rule, the signal is heard at a circuit resistance of no more than 80 Ohms. The dialing mode itself occurs when the pointer is positioned - checking the diodes. 
It is also useful to check the integrity of the probes themselves by testing them by connecting them to each other. Since with frequent use they may be damaged, especially at the point where the wire enters the probe tube. Before each measurement, be sure to make sure that there is no voltage in the area where you will connect the test leads, otherwise you may burn the device or create a short circuit.
Safety precautions when working with a multimeter
- ⚡ do not take measurements in a damp room
- ⚡ do not switch measurement limits during the measurements themselves
- ⚡ do not measure voltage and current if their values are greater than those for which the multimeter is designed
- ⚡ use probes with good insulation
I hope this material helped you become familiar with the basic operating parameters of a multimeter. And you can safely and productively use it during repair work.
A home technician periodically needs to measure circuit parameters. Check what voltage is currently in the network, whether the cable is frayed, etc. For these purposes there are small devices - multimeters. With small size and cost, they allow you to measure various electrical parameters. Let's talk about how to use a multimeter further.
External structure and functions
Recently, specialists and radio amateurs mainly use electronic models of multimeters. This does not mean that switches are not used at all. They are indispensable when electronic devices simply do not work due to strong interference. But in most cases we are dealing with digital models.
There are different modifications of these measuring instruments with different measurement accuracy and different functionality. There are automatic multimeters in which the switch has only a few positions - they select the nature of the measurement (voltage, resistance, current) and the device selects the measurement limits itself. There are models that can be connected to a computer. They transfer measurement data directly to a computer, where they can be saved.
But most home craftsmen use inexpensive models of the middle class of accuracy (with a bit resolution of 3.5, which ensures an accuracy of 1%). These are common multimeters dt 830, 831, 832, 833. 834, etc. The last number shows the “freshness” of the modification. Later models have wider functionality, but for home use these new features are not critical. Working with all these models is not much different, so we will talk in general about the techniques and procedures.
Structure of an electronic multimeter
Before using a multimeter, let's study its structure. Electronic models have a small liquid crystal screen on which measurement results are displayed. Below the screen there is a range switch. It rotates around its axis. The part on which the red dot or arrow is marked indicates the current type and range of measurements. There are marks around the switch that indicate the type of measurements and their range.
Below on the case there are sockets for connecting probes. Depending on the model, there are two or three sockets; there are always two probes. One is positive (red), the second negative is black. The black probe is always connected to a connector labeled “COM” or COMMON or that is labeled “ground.” Red - into one of the free slots. If there are always two connectors, no problems arise; if there are three sockets, you need to read the instructions for which measurements to insert the “positive” probe into which socket. In most cases, the red probe is connected to the middle socket. This is how most measurements are carried out. The upper connector is necessary if you are measuring a current of up to 10 A (if more, then also in the middle socket).
There are tester models in which the sockets are located not on the right, but at the bottom (for example, the Resanta DT 181 multimeter or the Hama 00081700 EM393 in the photo). In this case, there is no difference in connection: black to the socket with the inscription “COM”, and red, depending on the situation - when measuring currents from 200 mA to 10 A - to the far right socket, in all other situations - to the middle one.
There are models with four connectors. In this case, there are two sockets for measuring current - one for microcurrents (less than 200 mA), the second for current strength from 200 mA to 10 A. Having understood what is in the device and why, you can begin to figure out how to use a multimeter.
Switch position
The measurement mode depends on the position of the switch. There is a dot at one of its ends, it is usually tinted white or red. This end indicates the current operating mode. In some models, the switch is made in the form of a truncated cone or has one pointed edge. This sharp edge is also a pointer. To make your work easier, you can apply bright paint to this pointing edge. This could be nail polish or some kind of abrasion-resistant paint.
By turning this switch you change the operating mode of the device. If it stands vertically up, the device is turned off. In addition, there are the following provisions:
- V with a wavy line or ACV (to the right of the “off” position) - AC voltage measurement mode;
- A with a straight line—DC measurement;
- A with a wavy line - determination of alternating current (this mode is not available on all multimeters; it is not present in the photos above);
- V with a straight line or the inscription DCV (to the left of the off position) - for measuring DC voltage;
- Ω - resistance measurement.
There are also provisions for determining the gain of transistors and determining the polarity of diodes. There may be others, but their purpose must be found in the instructions for a specific device.
Measurements
Using an electronic tester is convenient because you don’t have to look for the right scale, count divisions, and determine the readings. They will be displayed on the screen accurate to two decimal places. If the measured value has polarity, then a minus sign will also be displayed. If there is no minus sign, the measurement value is positive.
How to measure resistance with a multimeter
To measure resistance, move the switch to the area indicated by the letter Ω. Select any of the ranges. We apply one probe to one input, the second to the other. The numbers that appear on the display are the resistance of the element you are measuring.
Sometimes what appears on the screen is not numbers. If 0 “jumps out,” then you need to change the measurement range to a smaller one. If the words “ol” or “over” are highlighted, the value is “1”, the range is too small and needs to be increased. That's all the tricks for measuring resistance with a multimeter.
How to measure current
To select a measurement mode, you must first determine whether the current is direct or alternating. There may be problems with measuring AC parameters - this mode is not available on all models. But the procedure is the same regardless of the type of current - only the position of the switch changes.
D.C
So, having decided on the type of current, we set the switch. Next, you need to decide which socket to connect the red probe to. If you don’t even know approximately what values to expect, so as not to accidentally burn the device, it is better to first install the probe in the upper (leftmost in other models) socket, which is labeled “10 A”. If the readings are small - less than 200 mA, move the probe to the middle position.
The situation is exactly the same with the choice of measurement range: first set the maximum range, if it turns out to be too large, switch to the next smaller one. Do this until you see the readings.
To measure current, the device must be connected to an open circuit. The connection diagram is shown in the figure. In this case, it is important to install the red probe on the “+” of the power source and touch the black probe to the next element of the circuit. When measuring, do not forget that there is power, work carefully. Do not touch the bare ends of the probe or circuit components with your hands.
Alternating current
You can try the AC current measurement mode on any load connected to a household electrical outlet and thus determine the current consumed. Since in this mode the device must be connected to an open circuit, difficulties may arise with this. You can make a special cord for measurements, as in the photo below. There is a plug at one end of the cord, a socket at the other, cut one of the wires, attach two WAGO connectors to the ends. They are good because they also allow you to clamp the probes. After the measuring circuit is assembled, we proceed to measurements.
Move the switch to the “alternating current” position, select the measurement limit. Please note that exceeding the limits may damage the device. At best, the fuse will burn out, at worst, the “filling” will be damaged. Therefore, we act according to the scheme proposed above: first we set the maximum limit, then gradually reduce it. (don’t forget about rearranging the probes in the sockets).
Now everything is ready. First, connect the load to the outlet. Maybe a table lamp. We insert the plug into the network. Numbers appear on the screen. This will be the current consumed by the lamp. In the same way, you can measure the current consumption for any device.
Voltage measurement
The voltage can also be variable or constant; accordingly, select the required position. The approach to choosing a range is the same: if you don’t know what to expect, set it to the maximum, gradually switching to a smaller scale. Do not forget to check whether the probes are connected correctly and into the correct sockets.
In this case, the measuring device is connected in parallel. For example, you can measure the voltage of a battery or a regular battery. We set the switch to the DC voltage measurement mode position, since we know the expected value, we select the appropriate scale. Next, use the probes to touch the battery on both sides. The numbers on the screen will be the voltage that this battery produces.
How to use a multimeter to measure AC voltage? Yes, exactly the same. Just choose the right measurement limit.
Testing wires using a multimeter
This operation allows you to check the integrity of the wires. On the scale we find a continuity sign - a schematic representation of the sound (look at the photo, but there is a double mode, or maybe there is only a continuity sign). This image was chosen because if the wire is intact, the device makes a sound.
We put the switch in the desired position, the probes are connected as usual - into the lower and middle sockets. We touch one edge of the conductor with one probe, and the other with the other. If we hear a sound, the wire is intact. In general, as you can see, using a multimeter is not difficult. Everything is easy to remember.
Modern cars cannot do without electronics; moreover, they are simply packed with electrical circuits and devices. In order to quickly diagnose faults in the electrical circuits of a car, you at least need a device such as a multimeter.
In this article, we will look at the most common modifications and discuss in detail how to use a multimeter for dummies, i.e. for those who have never held this device in their hands, but would like to learn.
Basic connectors and functions of the multimeter
In order to better understand what we are talking about, we will provide a visual photograph of the multimeter and analyze the modes and connectors.
Let's start with the connectors, where to connect the wires. The black wire is connected to a connector called COM (COMMON, which means common). The black wire is always connected only to this connector, unlike the red wire, which in most cases has 2 connectors for connection:
- VRmA connector - used to measure voltage, resistance and currents above 10 A (Amps);
- 10A connector - used for measuring currents up to 10 A.
Multimeter Functions and Ranges
Around the central pointer you can see ranges separated by white outlines, let's look at each of them:
- DCV - (DC - direct current, V - voltage) using this range, DC voltage is measured. The scales indicate volts and millivolts;
- ACV - (AC - alternating current, V - voltage), accordingly, alternating current voltage is measured;
- DCA - (DC - direct current, A - Amperes) measurement of direct current (the range is indicated on the device from 200 microamps to 200 milliamps);
- 10A is a separate range for measuring higher DC current; for this you need to move the red wire to the upper connector;
- hFE - transistor test mode;
- Omega - resistance measurement range.
Battery DC voltage measurement
Let's give a clear example of how to use a multimeter, namely, we will measure the DC voltage of a regular battery.
Since we initially know that the DC voltage in the battery is approximately 1.5 V, we can immediately set the switch to 20 V.
Important! If you do not know the DC voltage in the instrument or device being measured, you must always set the switch to the maximum value of the desired range and, as necessary, reduce it to reduce the error.
We turned on the desired mode, go directly to the measurement, apply the red probe to the positive side of the battery, and the black one to the negative side - look at the result on the screen (the result should show 1.4-1.6 V, depending on the condition of the battery).
Features of AC voltage measurement
Let's look in detail at what you need to pay attention to if you measure AC voltage.
Before work, be sure to check which connectors the wires are inserted into, because if, when measuring alternating current, the red wire is inserted into the connector for measuring current (10 A connector), a short circuit will occur, which is extremely undesirable.
Again, in case you do not know the AC voltage range, then set the switch to the maximum position.
For example, in everyday life we know that the voltage in sockets and electrical appliances is approximately 220 V, so the device can be safely set to 500 V from the ACV range.
How to measure current leakage in a car with a multimeter
Let's look at how to measure current leakage in a car using a multimeter. First turn off all electronics and remove the key from the ignition. Next, you need to remove the negative terminal from the battery (leave the positive terminal unchanged). We set the multimeter to the 10 A direct current measurement mode. Don’t forget to move the red wire to the appropriate connector (the top one, corresponding to 10 A). We connect one probe to the terminal on the disconnected wire, and the second directly to the negative of the battery.
After waiting a little until the values stop jumping, you will see the required current leakage value in your car.
What leakage value is acceptable
- The minimum acceptable value is 15 mA;
- The maximum current leakage value in a car is 70 mA.
If you have exceeded the maximum value, then you need to move on to searching for a leak. Leaks can be caused by any electrical equipment in the car.
Any home DIYer who has at least basic knowledge of electrical engineering should know how to use a multimeter (tester). Despite the fact that a modern device has a lot of functions, capabilities and measurement limits, it is quite simple. The main thing is to learn how to correctly connect the measuring probes, understand the meaning of all the symbols printed on the front panel and be able to work with different ranges and modes, depending on the situation. To understand the details of this issue, we suggest using the following instructions for using testers in practice. As an example, in this article we will look at a digital device, which will be much easier to work with compared to a dial multimeter. If you have not yet purchased the device, be sure to check out ours.
What is important to know about the tester device
Before you start making any electrical measurements, it is worth understanding what the device itself is and what its functions are. All information is printed on the front panel. You can learn how to use a multimeter of the selected model based on the following generally accepted notations:
- ON/OFF – button to turn the device on/off (on some testers it may not be present; in this case, the device will be turned on by turning the range switch);
- DCA (or A-) – direct current;
- ADCA – alternating current;
- ACV (V~)/DCV (V-) – alternating/direct voltage;
- Ω – resistance.
To take readings, you need to use a rotary switch, which allows you to set different operating modes of the multimeter and select the measurement range.
One of the important points in mastering the question of how to use a digital multimeter is the correct connection of the test leads to the appropriate connectors. The correctness of the measurements taken will depend on this. In order not to make mistakes, there are simple rules:
COM - black size on the left, universal connector in the center, connector for measuring high currents - on the right
- COM connector is common, it is used to connect the negative black measuring wire;
- to connect the red positive probe, one of the sockets for measuring voltage (V), resistance (Ω), current (mA, A) can be used, while it should be taken into account that, as a rule, there are two current sockets (for working with low-current circuits and with current up to 10/20 A depending on the tester model).
But it is also necessary to take into account that when measuring voltage or current, measuring probes installed in reverse will lead to a change in the polarity of the received data, which will be reflected on the display by the appearance of the “-” sign. The digital values will be correct. This is how digital devices differ from analog ones. In the latter, the arrow most often goes beyond the scale, and in some cases such work can lead to damage to the device.
Instructions on how to use a multimeter for dummies
The main purpose of any tester is to measure electrical quantities. When measuring current, a device connected to a circuit is connected to an open circuit (in series), and in order to use the tester as a voltmeter, it is connected to the circuit in parallel.
Using a Digital Multimeter to Measure Voltage
The method for measuring DC voltage is quite simple.
- Using the rotary switch, select the type of quantity being measured and the measurement limit.
- Setting the limit can be done after the user has determined what the approximate value of the measured voltage is. A hint can be the markings on batteries or parts of electrical circuits. The limit should always be greater than the measured value in order to prevent overloading of the device elements and its failure.
- In accordance with the instruction manual, the test leads must be connected to the terminals/terminals (black - to “minus”, red - to “plus”).
- We get the DC voltage value on the tester display.
measure the voltage of the electrical network
Another way to determine the measurement limit is to initially set the connected device to the largest possible measurement limit. Then, after taking readings, to improve the accuracy of the data obtained, you can reduce the limit to the nearest higher value, comparing it with the measured readings. There are no fundamental differences in how to take data on DC and AC voltage. The only difference is to switch the tester to the desired mode. The above algorithm then works.
Practical example of using the voltage measurement function
One of the most common operations in which you need to measure voltage is checking the condition of batteries. Moreover, it can be either an ordinary finger-type or an automobile one. In any case, it would be useful for a home craftsman to know how to properly use a multimeter in such a situation. If we are talking about AA batteries, measurements are performed as follows: the switch is set to the desired DC voltage limit. The resulting value must correspond to the nominal value. A deviation of ±10% from the nominal value is considered normal.
How to measure current
Before using a tester (or multimeter) to measure current, you need to decide whether the device under test operates with alternating or direct current. In addition, you need to know the approximate value that will be obtained as a result. This will allow you to correctly select the mA or 10/20 A socket used for work. Even if you have no idea how much current you will get in the end, solving the problem is simple. It is enough to first set the maximum limit, and then, based on the data obtained, if necessary, re-measure the value by moving the measuring probe and switch to a smaller range.
Testing circuits with a multimeter
Continuity testing is one of the main modes, which is often used in household use of multimeters to determine breaks or short circuits in a circuit. It is enough just to set the desired mode on the tester, turn off the power (including low-power ones such as batteries), discharge the capacitors, install the measuring probes and connect them to the required points of the electrical circuit.
For the convenience of the user, in the absence of breaks, most models are equipped with a buzzer, the signal of which makes it easy to navigate the results. In addition, in this case the resistance value or “0” will be displayed on the display. The absence of sound or the display of “1” on the screen will mean an open circuit in the circuit being tested. You can find out more about the continuity of wires, switches and other devices in.
Resistance measurement
A huge “advantage” of the resistance measurement operation itself is that when measuring it using a multimeter, it is almost impossible to damage the device or part in the equipment being repaired. To perform the operation correctly, you need:
- set the rotary switch to sector Ω,
- turn off the power, remove the batteries, accumulator,
- select the most suitable measurement limit,
- connect to the terminals of the circuit element being measured,
- take readings.
The whole procedure is quite standard. The only important difference is that after taking measurements, you may see "OVER", "1" or "OL" on the display. This means that an overload has occurred and the measurements must be repeated by switching the device to a larger range. Also, the display may show “0”, which means that the limits need to be lowered. To successfully use the resistance measurement function, knowledge of these simple rules will be quite enough.
Capacitance measurement
Radio amateurs and electricians who repair household appliances often need to measure the capacitance of capacitors. This issue is no less relevant for machine tool owners who periodically need to select the capacitor capacity when connecting a three-phase motor to a single-phase network to optimize the operation of the motor. These operations are performed by analogy with measuring resistance.
An important difference lies not only in the position of the switch, which must be set to the appropriate mode and range, but also in the mandatory pre-discharge of the capacitors. Otherwise, at a minimum, incorrect readings will be obtained (when working with low-capacity elements), and at maximum, the device will fail. As a rule, for operation in capacitance measurement mode, manufacturers provide separate sockets in the multimeter.
Detailed video instructions
In the first part of the video you will find general information on how to use a multimeter and learn how to measure DC and AC voltage.
After watching the second part, you will learn how to measure resistance, test circuits, check diodes, use the built-in generator, and also measure the amount of electric current.
Multimeter Safety
There are several potentially dangerous situations in which simple user carelessness can lead to instrument failure and failure of the equipment being tested.
- If it is necessary to measure voltage, the probes are installed correctly, and the switch is in any position other than voltage (on resistance, current).
- If you want to measure current, the test probe will be installed in the low current socket and the switch will be set to measure high current.
- When testing or measuring resistance in equipment, it is necessary to remove all batteries installed in it, since operation in this mode will damage the device.
- When operating in the continuity mode, if there are charged capacitors (capacitors) in the circuit, it is necessary to discharge them by short-circuiting them. When operating circuits with high-capacity elements, discharge can be performed through an incandescent lamp. Ignoring this rule may cause the multimeter to burn out.
All of the above situations lead not only to material losses, but also to increased danger for the person working with the tester. If you use the multimeter incorrectly, working with electricity can lead to accidental contact with live parts under high voltage, and this is already life-threatening. Otherwise, it is enough to follow simple rules and laws of electrical engineering to easily master working with a multimeter in all its modes and successfully carry out the necessary measurements without turning to specialists.
Modern cars are equipped with various electrical appliances that often break down and need to be checked.
How to choose a multimeter?
Currently, there is a wide range of multimeters on the market - from simple chopper exposure meters and tachometers to multifunction devices with ten different scales or digital displays. The picture shows: A Sparktune: shutter speed meter, voltmeter, ammeter. B Autoranger: shutter speed meter, voltmeter, ohmmeter, ammeter, tachometer. B Testune: shutter speed meter, voltmeter, ohmmeter, ammeter, tachometer. D Hawk: shutter speed meter, tachometer. E Avometer 2003: voltmeter, ammeter, ohmmeter. F CAB-100: battery tester.
One way to check the condition of electrical circuits is to connect a simple test lamp in the area between the current-carrying wires and ground. However, this method allows you to establish only the fact that current is supplied to a certain point in the area.
For a more accurate test, meters are used to determine the voltage supplied to an electrical system component and the resistance of that component or the circuit as a whole.
Multimeters
In stores that sell automotive accessories, you can purchase measuring instruments designed specifically for cars. The most useful devices are multimeters, which, as their name suggests, measure various characteristics of the electrical system.
Cars use direct current, and using a multimeter you can measure its strength, as well as the voltage and resistance at a specified point. Some multimeters also take readings of motor speed and contact dwell time.
Before each measurement, it is necessary to reset the previous readings, especially if you plan to work with small quantities (for example, resistance).
Do not use measuring instruments with moving needles to check electrical system components. Otherwise, you may over-stress and damage them. Use digital meters.
How to use a multimeter
Check the resistance of the high voltage wire by setting the multimeter to ohmmeter mode and taking readings at both ends of the wire.
A multimeter can be used to measure voltage, current, and resistance. Some similar devices also measure contact delay and motor speed. To obtain reliable results, the sensors must be connected correctly.
To measure the voltage on the battery, connect a sensor between the pins. To measure the resistance of a high voltage wire, connect sensors to both ends of the wire.
Switch the multimeter to ammeter mode and connect it to the shunt to measure the amount of current produced by the generator.
To measure the current produced by a generator or dynamo, connect a multimeter across a shunt. Measure the voltage of a coil or other circuit element by connecting one probe to it and the other to ground.
Reading the readings
To measure voltage, you need to switch the multimeter to voltmeter mode and connect one sensor to the circuit and ground the second.
When using a multimeter, you must correctly connect its contacts to the system components. The connection method depends on the polarity of the vehicle. In a car with negative grounding, it is necessary to connect the contact marked (-) to the body, and in a car with positive grounding, the contact marked (+) must be connected to the body. Refer to the instruction manual to check polarity.
Make sure that the contacts are securely fastened, and if necessary, clean them of rust and paint so that the readings are accurate. Sandpaper works well for cleaning.
Working in the engine compartment, attach the sensor to the ground clamp on the battery
Battery check
Set the multimeter to the appropriate settings and connect it to the battery terminals. The measurement result should be approximately 11-12V (at low and high charge levels, respectively).
If, according to the multimeter, the voltage is 10V or less, it can be assumed that there is damage in one of the battery cells. Connect the ground contact to the car body and take readings again. They should not differ from the results of the previous measurement. If this is not the case, check the tightness of the contacts.
Connect one multimeter probe to ground and the other to the starter solenoid. Take readings again. If readings are low, check the connection between the battery terminal and the starter solenoid.
If during measurement the readings on the contacts are too low, they must be secured before checking other components of the circuit. Clean problem areas from dirt and rust and re-measure. When the results of all measurements are approximately equal, they can be used for comparison when inspecting other components of the circuit.
Checking devices
Checking the tachometer
To test a new tachometer, you need to connect the multimeter to the terminal on the back of the device and ground. When current is applied to the device, the multimeter will record readings. This technique can be used for any device.
Many devices operate on current that passes through a voltage stabilizer. If several instruments display incorrect readings at once, the stabilizer may be faulty. To check, you need to connect a multimeter to the output connector and turn on the ignition.
Stabilizer check
In modern cars, some devices are powered by a voltage stabilizer. If the stabilizer breaks, the instrument readings are distorted. Before checking each device, you need to check the stabilizer itself by connecting a multimeter to its output connector and ground.
The multimeter should show approximately 10V, small deviations are due to the action of the rheostat. A strong deviation indicates that the multimeter needs to be replaced.
Checking the fuel level sensor
Disconnect the wiring from the sensor terminal and connect a multimeter between the non-working terminal and the ground point. Indications may vary depending on the position of the float. If readings cannot be taken, the sensor must be repaired or replaced.
The fuel tank sensor has a variable resistance resistor, the serviceability of which can be checked using a multimeter.
Disconnect the wiring from the sensor and connect a multimeter between the non-working terminal and the ground point. If the sensor is working properly, the multimeter should show a certain value. To carry out a full check, it is necessary to take readings with a full, half-empty and empty tank.
The readings should be in a logical sequence with approximately equal intervals. If the values are equal, most likely the sensor has shorted and is giving incorrect readings.
Ignition check
When testing a low voltage circuit, it is necessary to close it by closing the breaker contacts.
If an additional resistor is used in the coil, its action will cause the voltage at the input terminal to be lower (about 6-8V). To check the ignition voltage, connect a multimeter to the coil and ground. Turn the starter on and off briefly to bypass the additional resistor. The multimeter should show about 12V. Disconnect the multimeter from the coil.
If the value does not change, the fault lies in the low voltage circuit itself or the solenoid terminals.
Test these components by measuring the voltage drop across them. Connect the sensor between the terminals on the coil and to ground.
Close the contacts and switch the multimeter to low voltage mode. It should show 0-0.5V. If the reading is greater than 0.5V, the terminals on the coil are not working properly.
Switch the multimeter to high voltage mode and open the contacts. The readings at the input and output must match.
Zero voltage may indicate a distributor failure. In order to verify this, you need to turn off the distributor. If the voltage does not appear after turning off the distributor, most likely the fault lies in the coil itself.
Checking high voltage wires
To check high voltage wires, you need to switch the multimeter to ohmmeter mode. If the car operates with intermittent ignition, it can be assumed that one of these wires is faulty.
Determine the type of wires. Carbon alloy wires have a resistance of 10,000-25,000 ohms. Copper-plated wires have low resistance, but are equipped with radio suppression plugs with a resistance of 10,000 Ohms.
Disconnect the spark plug wires, remove the distributor caps, and measure the core resistance at both ends. Make sure the readings are correct.
To check the insulation, measure the resistance of the core and the surrounding plastic. If the wire is in good condition, the readings should be the same.
Checking the charging system
Start the engine, wait until it reaches normal temperature, and then turn it off.
Switch the multimeter to the desired mode (0-20V) and connect it to the battery terminals. Start the engine and take readings, then gradually increase the speed to 2000 rpm, paying attention to the multimeter display.
If the system is working correctly, the voltage will initially rise as the motor speed increases and then stop.
The maximum reading is 13.5-14.5V (depending on the car model). If the voltage does not increase, there may be a problem with the charging system.
Battery charging and discharging counter
There are special multimeters that take readings from the battery under high load (for example, during startup). This multimeter is a voltmeter with two teeth connected by a powerful resistor.
When the teeth touch the battery terminals, the multimeter takes readings. If the battery is good, the multimeter will show approximately 9V.
For such a check, you can use a regular multimeter. Disable the ignition system by de-energizing the coil. Connect a multimeter to the battery terminals, ask an assistant to turn on the starter for a few seconds and take readings during this time. As in the previous case, the reference value is 9V.
Current measurement
Measuring the current produced by a generator or dynamo often causes certain difficulties, because... this value is too large for most measuring instruments.
For this, an additional element called a shunt is used. A shunt is a resistor with a certain resistance. The multimeter is connected to the electrical system through a shunt, determines pressure drops and calculates the current strength. In some cases, the shunt is supplied with a multimeter. If this is not the case, read your vehicle's owner's manual to find the correct shunt.
