What it is
To check the current strength in high voltage electrical wires without breaking them by connecting an ammeter in series, a current clamp is usually used. In fact, the name of a multimeter with clamps is an incorrect expression.
An additional headset is connected to the devices
It is a current transformer. It has a built-in sliding wire with high magnetic permeability, consisting of two separate magnetic circuit side elements of the same shape and size. The secondary winding includes a meter or mechanical ammeter. The appearance is similar to ordinary pliers with a device.
For your information. To ensure safety, the pliers have long dielectric handles. The current passes through the transformer and is measured at the same time.
Pliers help with work
The composition of the instrument itself is simple. The antennae of the device are covered with insulating material and made of transformer steel. With the primary winding, an electrical wire is created and one curl is made. And the number of turns in the secondary is determined by the expected currents for measurements. The winding covers the entire structure. The insulation hides the entire winding.
In the form of a fraction, a marking is left on the tool with a transformation ratio that is the ratio of the indicated current in the primary winding and the secondary winding. In the device, the ammeter is located in the secondary winding and does the job of determining the current of the wire that encircles the structure.
There are two types of current measuring elements:
- less than 1000 Volts;
- for high voltage wires (more than 1000 Volts).
You cannot touch bare wires with your hands.
In everyday life, electricians use the first type of construction. More advanced devices perform the role of an ammeter, determining alternating current simultaneously with a voltmeter, ohmmeter and others. A multimeter that stands out from the rest is based on the Hall principle and measures not only alternating current, but also direct current. The sensor does not get confused about the direction of the field, reacting only to the voltage amplitude. It has a fast response to changes in current, which allows you to record transmission accuracy. But clamps with the Hall principle have no special advantages; it is the same ordinary multimeter for an ordinary person who does not understand physics.
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How to choose
Today, there are many testers on the market with and without clamps. The price range is not that wide. The problem of choice arises. First of all, you need to decide what it is needed for, what tasks it should solve.
If there is a need for non-destructive testing, it is necessary to quickly measure the currents on the incoming wires at the dacha or at the meter, then purchasing a multimeter with a current clamp would be the right solution.
If you need to measure currents in a car's electrical wiring, you will have to purchase a device with Hall sensors, although they are a little more expensive.
In addition, multimeters, depending on the manufacturer, can measure alternating and direct currents and voltages, resistance, capacitance, frequency, and power.
The set of functions depends on the hardware developers. But there is no need to strive for versatility; this affects the price and characteristics of the tester. It is good if the device comes with detailed operating instructions. After taking into account all the factors, you can make a purchase.
Principle of operation
The multimeter is based on a current transformer with one turn. The voltage flow itself is determined in the primary winding, which will be an electrical wire or bus. The ammeter is connected to the secondary, which contains more than one turn. In the device it is located on a detachable magnetic circuit. The current value that is supposed to be studied in the conductor is obtained by measuring the voltage flowing through the secondary winding. In this case, the already determined transformation coefficient is taken into account.
There are several types of devices
Note! Measuring current with a clamp-on multimeter is convenient and simple and will not cause problems.
Device parameters and measurement progress
There are several ways to measure. You can detect the current flowing through a conductor that is placed in a clamp at a right angle. The indicator will show the desired range. The second method is suitable for measuring current passing through several conductors. The latter (uncommon method) amplifies signals.
The size of the conductor to be measured is limited using a handle. The process goes like this: the pliers move apart, a wire is passed through, the handle is released and the pliers are closed. The subsequent steps are similar to using a simple tester. The insulation of the electrical wire does not matter. It is important to cover only the tire.
This device is easy to measure in hard-to-reach places
The digital or mechanical indicator will show the current value. Some devices can record results for convenience. The value remains after the magnetic circuit is separated from the conductor.
The ammeter measures the current flowing through the secondary winding through the occurrence of electromagnetic induction.
How to measure
Using a multimeter with a clamp meter is easy. First you need to set the AC or DC current measurement mode. Using the switch on the multimeter, you select the required sector with mode designations and stop on the scale with the expected values.
After this, pressing the lever opens the pliers. The conductor to be tested is inserted into the gripping area, and the pliers close. The display will show the instrument readings.
Some testers with clamps have a special button that fixes the reading. Then just click on it to save the measurement result. This is convenient when taking measurements in hard-to-reach places.
If the device shows 1, then the current value exceeds the measurement limit, and you need to set the switch to a higher value. If the reading is 0 or close to it, you need to go to the lower scale.
The measurement scale must be selected so that the instrument readings are in the region of maximum values. In this case, the measurement error will be minimal.
Sometimes, the readings of a multimeter with a current clamp are close to 0, but measurements are necessary. In this case, use a simple method. The conductor is twisted into several turns and all the wires are grabbed with pliers. A value will be recorded on the device.
It must be divided by the number of wires passing through the clamps and obtain the desired value of the current passing through the conductor.
Advantages and disadvantages of a multimeter
There are two types of current devices: digital and pointer. Clamp meters with digital display are much easier to use. They automatically calibrate the measurement range and record results in the device's memory. But their main drawback is the low accuracy of the results of measuring currents other than the shape of a sinusoid.
There are mechanical variations
The dial multimeter began to be used earlier. Its low cost and high measurement accuracy allows it to compete with digital ones. Unlike a digital multimeter, it has a narrow operating frequency range. The mechanical indicator makes it more sensitive to drops or shocks, which may reduce the accuracy of the results.
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There are digital variations
Another type of clamp is used with an oscilloscope or multimeter. It differs only in that it does not include a display or mechanical indicator to display the received signal. Such devices are highly accurate, but do not work independently and require a separate device to determine the current.
Many electricians work with high voltage current variations. They are used for circuits with voltages greater than a thousand volts. Such instruments have improved electrical insulation. This increases the safety of the electrician carrying out the measurements. With their help, you can monitor the current at different transformer substations and distribution nodes. The obvious advantage of high-voltage models is the safe operation of high-voltage equipment. But the operating range for AC is too narrow.
DC Clamps
DC clamps have in their structure a sensitive element in the form of a sensor. It will record alternating and direct voltage during electrical current fluctuations.
The main advantage of such a model is its effectiveness in relation to electrical appliances with a similar structure.
The sensors are capable of detecting minimal voltage surges during device operation. The cost of such equipment is quite high.
Measurement with current clamps must be carried out in compliance with polarity. Incorrect placement of sensitive elements can cause damage to the electrical device or cause a short circuit.
How to use a multimeter
Using a multimeter with current inserts, you can examine the voltage of the residential network. To do this, you need to lock the range switch in “ACA 200”. An insulated electrical wire introduced into the apartment must be grasped with open pliers. The measurement readings will appear on the indicator. They are multiplied by 220 volts (the value of the apartment’s network voltage), and the cosine is not taken into account (equal to 1). The answer will help check the activity of the device installed to measure energy consumption, etc.
TB should be observed
When deciding to buy a current clamp, you need to determine the required set of measurement limits for different types of current, the shape, the accuracy of the results, the operating range, additional properties, and financial capabilities. Then you will be able to purchase a convenient tool. It can be used at home without any problems.
Criterias of choice
There are hundreds of models on the market and in online stores that are designed for carrying out measuring work in the electrical network. You need to choose an option that is easy to use and extremely understandable. An electrician's assistant should not buy expensive professional equipment; this will not improve his skills. It is better to start with easy tools, gradually learning new things. Moreover, even some professionals bypass complex pliers with wide functionality, since they understand that they will not need most of the capabilities during their work.
A budget product is good, but you can’t save much on it. Because the accuracy of measurements will depend on their quality. Also, you should not pay attention to counterfeits of branded instruments, since their level of assembly is far from normal. They can break during measurements. And using such equipment is much more dangerous, since the plastic can fall apart or melt.
