When assessing the state of existing electrical installations or performing repair work under voltage, electricians have to measure and compare the values \u200b\u200bof the currents flowing through various circuits. This allows you to analyze the operating scheme, and promptly eliminate emerging faults.
Quite often, all this must be done without breaking electrical circuits so as not to disrupt technological process power supply to consumers.
There are two ways to measure load currents without interrupting the power supply:
1. ordinary ammeters, creating through them at first bypass shunt circuits and putting them into operation due to an artificial break in the current in a previously prepared place. At the end of the measurements, it is required to restore the electrical circuit, perform all previous technological operations in the reverse order;
2. using a tool specially designed for this - a current clamp.
The first measurement method is complicated, laborious, dangerous, requires highly skilled workers, good preliminary training. Therefore, they try to use it only in extreme cases, and in everyday practice, measurements are performed with a current clamp.
What are the types of clamp meters
Most often, in practice, they are found with direct (rectified) or alternating sinusoidal current. For both of these types, various designs of clamps have been created, with which it is possible to measure the magnitude and even the direction of power flow without interrupting the power supply circuit of consumers in an operating electrical installation.
The photo below shows the measurement of the deviation of the current vector angle from the direction of the base voltage in the measuring circuits of protective devices.
A method for measuring leakage currents through a broken insulation of a car's electrical equipment using a DC clamp and an ammeter is shown in the photo.
The measuring circuit used is assembled in such a way that the clamp themselves show the current flowing through the wire connected to the ammeter clamp. Both devices demonstrate the same value, although they operate at different sensitivity ranges.
This example clearly demonstrates the convenience and accuracy of measurement with various devices. Clamp meter measuring DC current is less common than AC designs, but in recent times their production has increased significantly.
It should also be borne in mind that manufacturers of measuring equipment have now set up the production of combined use clamps, which can work in DC and AC circuits. This design, for example, is embodied in the Fluke 376 and the like.
The current clamps shown in the first three photographs have a digital display that immediately displays the primary values \u200b\u200bof the measured parameters of the electrical circuit. But, in the arsenal of electricians' measuring instruments, a large number of instruments with pointer indicators and a scale consisting of several sub-ranges still work.
When using such structures, it is necessary to carefully read the reading, and sometimes enter correction factors.
By the magnitude of the applied voltage, current clamps are divided into devices that operate:
up to 1000 volts;
or above 1 kV.
They differ in the protection class of the applied insulation and require different compliance with safety rules.
In order to use any such devices correctly, you need to know the principle of their operation and design.
How a current clamp works
Device different models may vary significantly depending on the timing of their manufacture and the complexity of the internal circuit. But the principles of measurement and controls are almost identical everywhere. Therefore, we will take the Fluke 376 model as a basis for studying, which has great capabilities and, accordingly, has an increased number of functions and controls.
Principles of operation incorporated into the design
The dielectric housing of any device contains:
current transformer with (a) a detachable magnetic drive and a system of its control levers, (b) a secondary winding;
measuring system with information board;
controls and switching modes of operation;
contact sockets.
To power the current clamp, the electrical energy of the measured circuit or a set of autonomous voltage sources, for example, two AA batteries, can be used.
The work is based on an ordinary current transformer with a split magnetic circuit and a secondary winding, the turns of which are crossed by the magnetic flux, inducing a secondary current in them. Its value, and in some designs and direction, is determined by the measuring system, which displays the final result on the display, taking into account the transformation ratio in primary amperes.
To take a measurement, it is necessary to place a conductor with a current inside the magnetic circuit. For this:
by pressing a key, the moving elements of the magnetic circuit are bred;
a wire with a current is introduced into the formed gap;
release the key and track the full contact of the moving contacts.
When working inside cramped cabinets with a lot of electrical equipment, it is sometimes difficult to thread the tip of the sliding magnetic circuit through the current conductor. To simplify this operation, the Fluke 376 has an optional measurement probe. It is included in the set of the device and, if necessary, can be easily prepared for measurement.
For safe performance of work under voltage, the pliers are equipped with measuring leads with insulating tips and caps. When installed in the body of the device, they are recessed into its structure. Combined with well insulated ferrules, this reduces possible mistakes in work, to exclude unauthorized creation of accidental short circuits and receiving electrical injuries.
Current Clamp Controls
The positions of the mode dial are shown by inserting text in the third picture from the top. Their work is complemented by control buttons located on the body.
The ZERO button is used to switch within the clamp modes set by the central circular switch, and MIN / MAX - allows you to refine the measurement limit.
The INRUSH button is used to evaluate the inrush current. The convenience of using the device in a darkened workplace is significantly provided by the built-in backlight, which is put into operation by pressing the extreme right button below with lighting image.
To fix the current readings on the display, the HOLD button is installed at the side of the clamp.
For some models of current clamps, some of these functions may be absent or implemented in other ways, but the general principles of measurement are preserved for all such devices.
How to measure with a current clamp
Preparatory operations
Before each measurement, it is necessary to check the influence of extraneous voltage sources and the interference they create on the accuracy of the device.
Powerful asynchronous electric motors, power transformers and autotransformers, chokes, welding machines, during operation, can create strong electromagnetic fields that will induce the induced EMF in the magnetic circuit. To take them into account, the clamp is placed in the position of measuring alternating current, the sliding elements of the magnetic circuit are tightly closed and the zero current reading on the display is monitored.
Methods for measuring currents
The design of the measuring device allows you to determine the magnitude of the current simple actions: by setting the mode switches to the appropriate position and by inserting the conductor into the space of the sliding magnetic circuit. The numerical expression of the measured value is automatically displayed on the display.
This technology is used on all ticks without exception. But on advanced devices, you can use the IFLex sensor. It makes it easier to work in confined spaces.
A similar operation is always performed for a separate wire, because the current passing from it creates a magnetic flux in the magnetic wire or the IFLex sensor, which is converted by the clamp into a reading.
If two conductors with current are placed inside the magnetic circuit, then the magnetic fluxes from them will add up and the tongs will show the overall result.
Since there are no leaks with normal insulation, the currents in phase and zero will be equal in magnitude and oppositely directed, as shown in the photo by arrows and signs + I and -I. Each of them will create a magnetic flux that will add up and destroy each other's action. As a result, the scoreboard with normal isolation should display a zero result.
If the clamps show a different value in such a situation, then this is a serious reason for troubleshooting the current wiring.
Useful tips for measuring currents
Extra cable with plug and socket
To measure the current consumption of an electrical appliance, for example, an iron, it may be difficult with. In a solid cable, it is impossible to do this without opening it. The issue can be easily resolved by connecting the load through a split adapter.
Increased measurement sensitivity for low currents
With ordinary clamps, it can be difficult to determine the values \u200b\u200bof small currents due to the low sensitivity of the device. The way out of this situation is quite simple: pass the conductor with the measured current through the magnetic circuit of the current clamp several times, as shown in the photo above. In this case, the total magnetic flux increases in proportion to the number of turns and the display reading also increases.
It remains only to divide the count value by the number of turns and get the exact value even for small currents.
Please note that this technique is only suitable for working with flexible, insulated conductors.
Voltage measurement methods
The use of a current clamp in the voltmeter mode is, in principle, no different from similar measurements with other devices.
The detachable ends of the conductors are installed in the sockets of the claws, which are pre-switched to the voltage measurement mode by switches. The other ends of the insulated wires are applied to the potential terminals and read off the display, as shown in the photo above.
Features of measuring resistance, frequency. temperature
Methods for measuring power consumption
The current clamp does not have a direct method for measuring and reading power, but they can perform this operation indirectly. To do this, you need to determine by the methods described above:
- A probe with a black wire is installed in the corresponding black socket, and a probe with a red wire in the red socket, where there is a designation "A", that is, ampere.
- The toggle switch switches to the desired position: for AC measurements - AC, DC - DC.
- The measurement limit is set so that it is higher than the expected current level in the circuit. This will help prevent the appliance from burning out.
- The multimeter should be set at the maximum measurement limit.
- The multimeter probes are applied to the battery contacts.
- After the increase in the current on the screen stops, after about 1-2 seconds the probes are removed.
- V with a wavy line or ACV (to the right of the "off" position) - AC voltage measurement mode;
- A with a straight line - DC current measurement;
- A with a wavy line - determination of alternating current (this mode is not available on all multimeters, in the above photos it is not);
- V with a straight line or the inscription DCV (to the left of the off position) - for measuring DC voltage;
- Ω - resistance measurement.
- An ammeter is a specialized instrument for measuring current strength. It is used only in physics lessons, it is not used in everyday life.
- A multimeter is a multifunctional measuring instrument that allows, in addition to current, to check the voltage value and other characteristics of the electrical system. Such devices are widespread, used by professional electricians and in a domestic environment.
- Testers are simplified and obsolete multimeters. They are rarely used today, but used to be widespread.
- Modern measuring clamps are a device that does not require preliminary circuit breakage and load disconnection. Allows you to easily and safely determine the parameters of any electrical system.
- OOF - disabled device.
- ACV - AC voltage measurement mode.
- DCV - DC voltage measurement.
- ACA - AC current measurement mode.
- DCA - DC current measurement.
- Ω - resistance measurement.
- hFE - measurement of the characteristics of transistors.
- indicator of alternating voltage in the network and constant voltage of the battery or battery;
- direct and alternating current (amperage);
- resistance level;
- diode performance (dial mode);
- current frequency;
- temperature;
- capacitance value of the capacitor.
load current;
We can conclude that the power consumption is two kilowatts.
Checking the absence of extraneous consumers
With the help of a current clamp, you can check the unauthorized connection of consumers to the power cable. To do this, it is enough to install the clamps on the input board in the load measurement mode and, leaving the normal power on, turn off all lamps and release all sockets from the devices, that is, provide an idle run for the input cable.
If the clamp in this case shows a zero value, then there are no unauthorized connections and no leakage currents. Otherwise, it is necessary to carefully deal with the reason for the formation of such a load.
1. Any measuring device is designed for use under specific technical conditions and work with specific loads. You should familiarize yourself with these characteristics in advance and observe them during operation.
For example, Fluke instruments are labeled CAT III 600 V or CAT III 300 V. This indicates that electrical circuit the device is designed with protection against short-term overvoltages in the measured network up to 600 or 300 volts, respectively.
If the limit of the measured value is unknown, then the maximum value mode is set on the device.
2. Working insulation on the sliding magnetic circuit and measuring tips protects the user from creating unauthorized short circuits when working under voltage. It is necessary to monitor her condition. This position is especially important when measuring currents on bare, uninsulated wires.
3. The current clamp is a measuring instrument. They must undergo periodic metrological verification in an electrical measuring laboratory and have its stamp on the body or a verification certificate, the validity of which is limited.
4. Since current clamps are used for work under voltage, it is a prerequisite for them safe operation is a periodic test of the insulation layer for strength in an electrical testing laboratory with the execution of a test report and a corresponding stamp.
Without passing the insulation test and verification, the use of pliers in work, even just purchased from the manufacturer, is prohibited by the rules. Damage can occur if storage or transportation standards are violated. The pre-sale preparation of the tool in the store is not able to identify the defects that have arisen.
5. Before measuring resistances, make sure that there are no voltage potentials on them. They can not only affect the accuracy of the readings, but also damage and burn sensitive measurement circuits by generating dangerous currents.
6. Working with an energized current clamp is classified as life-threatening. Only trained and trained personnel with an electrical safety group of at least the third is allowed to it.
Content:One of the main parameters in electrical engineering is the current strength, which is an electric current in a certain amount passing through a conductor of a certain section. This value is of great importance for normal work electrical systems, so the question of how to measure the current with a multimeter often becomes relevant. This procedure is necessary in order to know exactly about a particular current level set for a particular circuit. The multimeter is the main instrument with which measurements are taken.
How to measure the current in an outlet with a multimeter
Before starting measurements, the measuring probes are first connected to the device. Each of them has its own color - black and red. The black probe is usually common, zero or negative, so it is connected to the bottom connector marked with COM symbols. Another red test lead is connected to the middle connector during measurements. There is a connector located at the top of the multimeter that connects the red test lead when measuring AC current up to 10 amps.
After connecting the probes, the desired operating mode is selected by turning the round switch and setting it to the desired position. If the value of the measured parameter is known in advance, then the set measurement limit should slightly exceed it. This measure allows you to protect the multimeter from burnout. In the event that there is no information about possible readings of the device, the maximum possible measurement limit is set.
When measuring voltage, the device is connected to the circuit in parallel, and for current measurements - in series. Measurement of semiconductors or resistance parameters is performed with the power off in this circuit. can also be measured with a multimeter. To do this, the switch must be set to the ACV position at around 750 volts, and then measure. The measurement is carried out in the same way in a network with a voltage of 380V. The strength of the current in the outlet is measured by setting the device to the AC current measurement mode.
How to measure the current of a transformer with a multimeter
Flow electric current in the transformer is carried out exclusively in a closed loop. In order to make current measurements, you must first connect some kind of load, and then a multimeter is connected in series with it in the circuit. In this case, the switch is also set to AC measurement mode. The red wire is connected to a separate output.
At the preparatory stage, you need to do the following:
After preparation, you can proceed to direct measurements. For this purpose, the multimeter must be sequentially connected to the break in the electrical circuit between the transformer and the load. The amount of current passing through the device will be displayed on the multimeter display. In the absence of a load, a limiting resistance can be included in the circuit - an ordinary light bulb or a resistor.
If the display does not show the current value, then the measurement limit is selected incorrectly and it must be reduced by one position. If there is no result, the procedure must be repeated and continue to do this until a value appears on the display.
How to measure battery current with a multimeter
Despite the external similarity, all batteries have different parameters and technical characteristics... In this regard, quite often it becomes necessary to check the performance of these elements, in particular, in measuring the current strength.
The main testing method concerns new batteries, allowing them to determine their performance at the time of purchase. To take measurements, the multimeter is set to the position corresponding to direct current. Further, the procedure will be as follows:
The normal amperage for a new battery is typically 4 to 6 amps. If the indicators are from 3 to 3.9A, this indicates a decrease in the battery's service life. Therefore, it can only be used in devices with reduced power. At lower rates, batteries can be used only in very weak devices or not used at all.
How to measure DC current with a multimeter
DC current measurement is carried out in the same way as for battery measurements. It's just that in this case, the multimeter is also used to check more powerful devices. First of all, these are either rectifiers used in industry and in everyday life.
For measurements with a multimeter, any two points are selected, between which the measuring device is connected in series. Connection must be made with mandatory polarity. If the multimeter is connected incorrectly, the display will show a value with a minus sign.
In the event that the value of the estimated current strength is greater than the uppermost measurement limit, it is necessary to set the switch to the "10A" position. At the same time, the measuring probe moves from the V ΩmA jack to the 10A jack.
How to measure AC current with a multimeter
Before starting measurements, it is necessary to determine exactly what current will be measured - alternating or direct. After that, the multimeter switch is set to the desired position. Next, you need to set the approximate force in this circuit in order to connect the measuring probe to the corresponding connector. If the current strength is supposed to be up to 200mA, the probe is connected to the "V ΩmA" jack, and if the current strength is more than 200mA - into the "10A" jack.
Sometimes it happens that there is no information about the current strength at all. Therefore, measurements should be started with the maximum value. If current appears on the display smaller value, then the plug needs to be rearranged to a different connector. If the current is again less than the required one, the plug is swapped again. If necessary, the regulator knob should be set to a lower level of amperage. Before starting measurements, you need to carefully study all the designations applied to the multimeter and then select only the desired symbols. All measurements should be carried out from maximum values \u200b\u200bto minimum values, this is a mandatory requirement when working with a multimeter.
The home craftsman periodically needs to measure the parameters of the circuits. Check what voltage is currently in the network, whether the cable is frayed, etc. For these purposes, there are small devices - multimeters. With their small size and cost, they allow you to measure various electrical parameters. We will talk about how to use a multimeter further.
External structure and function
Recently, specialists and radio amateurs mainly use electronic models of multimeters. This does not mean that the turnouts are not used at all. They are irreplaceable when, due to strong interference, electronic ones simply do not work. But in most cases, we are dealing with digital models.
there is different modifications these measuring devices with different measurement accuracy, different functionality. There are automatic multimeters in which the switch has only a few positions - they choose the nature of the measurement (voltage, resistance, current) and the device chooses the measurement limits itself. There are models that can be connected to a computer. They transfer the measurement data directly to a computer, where they can be saved.
But most do-it-yourselfers use inexpensive, mid-range models (3.5 bits, which provide 1% accuracy). These are common dt multimeters 830, 831, 832, 833.834, etc. The last figure 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 techniques and procedures.
The structure of an electronic multimeter
Before using the multimeter, let's study its structure. Electronic models have a small LCD screen on which the measurement results are displayed. There is a range switch below the screen. It rotates on its own axis. The part with a red dot or arrow indicates the current type and range of measurements. Around the switch, there are marks by which the type of measurements and their range are set.
Below on the body there are sockets for connecting probes. There are two or three sockets depending on the model, there are always two probes. One is positive (red), the other negative is black. The black test lead always connects to the connector labeled "COM" or COMMON or labeled "ground". Red - to one of the free slots. If there are always two connectors, no problems arise, if there are three sockets, you need to read in the instructions for what measurements to insert the "positive" probe into which socket. In most cases, the red test lead is plugged into the middle socket. This is how most measurements are taken. The upper connector is necessary if the current is up to 10 A to measure (if more, then also to the middle socket).
There are models of testers in which the sockets are located not on the right, but at the bottom (for example, the Resant DT 181 multimeter or Hama 00081700 EM393 in the photo). There is no difference when connecting in this case: black for the socket with the inscription "COM", and red according to the situation - when measuring currents up to 200 mA to 10 A - in the far right socket, in all other situations - in 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 a current from 200 mA to 10 A. Having understood what and why is in the device, you can begin to figure out how to use a multimeter.
Switch position
The measurement mode depends on which position the switch is in. There is a dot at one of its ends; it is usually tinted with white or red. This end indicates the current mode of operation. 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 it easier to work, you can apply bright paint to this pointing edge. It 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 straight up, the device is turned off. In addition, there are the following provisions:
There are also provisions for determining the gain of transistors and determining the polarity of diodes. There may be others, but their purpose should be sought in the instructions for a specific device.
Measurements
The use of an electronic tester is convenient because you do not need to look for the desired scale, count the divisions, determining the readings. They will be displayed on the screen with an accuracy of two decimal places. If the measured value has polarity, the minus sign will also be displayed. If there is no minus, the measurement is positive.
How to measure resistance with a multimeter
To measure resistance, move the switch to the zone marked with the letter Ω. We choose any of the ranges. We apply one probe to one input, the second to the other. Those numbers that will appear on the display are the resistance of the element you are measuring.
Sometimes the screen does not display numbers. If "jumped out" 0, then it is necessary to change the measurement range to a smaller one. If the words "ol" or "over" are highlighted, there is "1", the range is too small and should be increased. That's all the tricks for measuring resistance with a multimeter.
How to measure current
To select the measurement mode, you must first determine the DC or AC current. 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, set the switch. Next, you need to decide which socket to connect the red probe to. If you do not even know approximately what values \u200b\u200byou should 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 reading is small - less than 200 mA, move the probe to the middle position.
The situation is exactly the same with the choice of the measurement range: first, set the maximum range, if it turns out to be too large, switch to the next smaller one. So until you see the readings.
To measure the current strength, the device must be included in the open circuit. The connection diagram is given in the figure. In this case, it is important to set the red probe to the "+" of the power source and touch the next circuit element with the black one. Do not forget when measuring that there is food, work carefully. Do not touch the bare ends of the probe or circuitry.
Alternating current
You can try the AC measurement mode on any load connected to the household power supply and thus determine the current consumption. As in this mode the device must be included in the open circuit, this may be difficult. You can, as in the photo below, make a special cord for measurements. At one end of the cord there is a plug, on the other - a socket, 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 can damage the instrument. In the best case, the fuse will burn out, in the worst case, the "filling" will be damaged. Therefore, we act according to the scheme proposed above: first we set the maximum limit, then gradually reduce it. (do not forget about rearranging the probes in the sockets).
Everything is now ready. First, connect the load to the outlet. You can use 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.
Measuring voltage
The voltage can also be alternating or constant, respectively, we select the required position. The approach to choosing a range is the same: if you don't know what to expect, set the maximum, gradually switching to a smaller scale. Do not forget to check if the probes are correctly connected to the right sockets.
In this case, the measuring device is connected in parallel. For example, you can measure the battery voltage or conventional battery... We set the switch to the position of the DC voltage measurement mode, since we know the expected value, select the appropriate scale. Next, with the probes, 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.
Continuity of wires with a multimeter
This operation allows you to check the integrity of the wires. On the scale we find the dialing sign - schematic representation sound (look at the photo, but there is a double mode, and maybe only a dialing sign). This image was chosen because if the wire is intact, the device emits a sound.
We put the switch in the desired position, the probes are connected as usual - in the lower and middle jacks. We touch one probe to one edge of the conductor, the other to 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.
The most important parameter of the electrical network is the current strength - a quantitative value that is equal to the amount of charge passing through the conductor cross-section for a certain time.
The current value is interconnected with the used in electrical networks cables and safety devices. The larger the cross-section of the wires, the more current can flow through them. Standard copper cables for the lighting system with a cross section of 1.5 sq. mm. are designed for a current of 16 A. Measurement of alternating and direct current must be carried out in all power grids at regular intervals, since the performance and safety of power supply largely depends on the value of this characteristic.
What devices are used to measure current?
Today, there are various measuring tools that allow you to accurately determine the current strength in a household electrical network. The most common meters are:
The most convenient and common means for measuring current strength is a multimeter. This device makes it possible to determine various parameters of the electrical network, but you need to work with it carefully, in particular, it is necessary to control the correctness of the selected mode. The standard device has 7 positions on the scale:
When checking the current value, the multimeter probes must be connected in series with the load, all other types of measurements require parallel connection.
The figure shows an example of the correct connection of the device.
To measure alternating current, select the correct mode, connect the device to the open circuit of the phase conductor and conduct the necessary tests.
To check the direct current, one clamp of the multimeter is connected to the positive terminal of the measured battery or battery, and the second to the wire through which the consumer of electric current is connected. Next, you need to set a suitable mode and carry out measuring work.
It is important to bear in mind that working with a multimeter is difficult and can pose a serious danger to humans. All studies should be carried out after disconnecting the mains and after checking the absence of voltage in the measured sections of the system. Any contact with bare wires can lead to injury and even death, therefore beginners are not recommended to carry out such work on their own.
A much simpler and safer method of measuring the current in an electrical circuit is the clamp-on technique. The figure below shows an example of a connected and ready-to-test device.
With the help of ticks, even a beginner can take measurements without putting himself in danger. The user only needs to turn on the appropriate operating mode (for checking household networks - the AC measurement mode), insert the measured conductor into a special hole between the mustache of the device and conduct tests.
The uninterrupted operation of electrical appliances largely depends on the voltage level in the network, the correct current supply, and the integrity of the wiring. You can measure AC voltage using a multimeter. it irreplaceable assistant in the timely identification of problems in the power grid and ensuring safe use household and professional appliances.
Features, functions, types of devices
This device is a universal recorder of a variety of electrical quantities. Depending on the lineup and the set of functions that they perform, multimeters have found their application, both in everyday life and in the arsenal of professional electricians.
An average cost multimeter can measure:
Devices of the new design may have a low-frequency generator and a sound probe. Among the entire range of products, it is worth highlighting 2 main types of devices.
Electronic (digital) type. The readings are displayed on a screen surrounded by seven-segment indicators. Most of them work in automatic mode, the limit value of the values \u200b\u200bis determined by the multimeter independently, based on the received data. You just need to choose the type of measurement. Other models can transfer data directly to a computer for further processing.
Arrow type. This kind of device will be a real lifesaver when strong interference breaks normal functioning electronic multimeter and completely distort the information.
At home, it will be enough to measure the current with an electronic type multimeter with a capacity of 3.5. These are devices like the dt 831, 832 or newer dt 834 modification.
Body elements
Since digital models have become more and more in demand, the designations and main characteristics of multimeters will be considered precisely on their example.
They are equipped with a liquid crystal display that provides the measured values. Slightly below is a switch rotating around its axis. It indicates the selected type and measurement range.
2 test leads with wires are connected to the sockets on the multimeter case: red or positive, black or negative.
A negative probe is always connected to the connector signed as "ground" or "COM". Positive connects to any other jack.
It should be noted that there may be 2, 3 or 4 connectors. Their number depends on the model and manufacturer. However, even in such multimeters, the socket for connecting only the positive probe can change, the negative one remains in the same place.
Tester operating modes
The operation of the multimeter and its modes is regulated using a switch. Its upper vertical position indicates that the device is turned off.
A turn in any other direction indicates a regime change and is indicated as follows:
All results are displayed on the screen of the tester in a matter of seconds, with an accuracy of hundredths reporting the value of the selected indicator.
The alternating current designation on any multimeter can be displayed in the form of AC symbols (alternating current). Accordingly, ACA is the AC current, ACV is the AC voltage. This is a current that changes the direction of movement a huge, but constant number of times in 1 second. In home networks, the frequency of change is 50 Hz.
Connection sequence
It is important to note that when starting to measure the AC level, it is not at all necessary to observe the polarity of connecting the probes. If its value is negative, then a minus sign will be displayed in front of the numbers on the screen.
We put the switch of the multimeter that measures this indicator in the appropriate position and set the measurement range.
The choice of measurement limits should be taken as responsibly as possible. If the measured current significantly exceeds the selected range, this can cause a blown fuse or, even worse, the entire multimeter.
Pay attention to the choice of connector (jack). Below it should be the maximum value of the current strength that you want to measure. 10 A means that the current is measured up to 10 A (quite large).
To regulate the measurement process, the switch is first set to the maximum permissible range of values, plug the test leads into the sockets. Further, as necessary, reduce the level.
To measure the strength of an alternating or direct current, the multimeter must be connected to the circuit in series with the load (flashlight, lamp, cooler, radio circuit, etc.). This is the basic rule for all electrical measuring instruments. That is, to measure the current, the multimeter is included in the "open" circuit.
How to determine the value of AC voltage in the network
An important point in determining AC voltage is the fact that the test leads of the multimeter are connected in parallel to the measured device. This is due to the fact that the voltage itself is the potential difference between two points.
You can use the same principle as in the case of alternating current... Adjust the range of value from maximum to minimum, not forgetting about the position of the probes.
As an example, a standard battery can be used to measure AC voltage. The switch is set to the appropriate mode, the range is set. In this case, the probes touch the battery parallel to each other on both sides. And you can instantly see how the screen displays the voltage value of the element under study.
With constant voltage, the situation is the same, only you need to remember to move the switch to the correct mode.
Regardless of the model and the specifics of the operation of the multimeter, it is important to follow the fire safety instructions, properly handle electrical devices without risking your health.
