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How to Use a Clamp Meter?
Resource Description
Electricians and technicians face numerous challenges while dealing with electrical equipment and circuits. Although modern test devices meet the high requirements set by technological advances, they require specific knowledge and skills on the part of the people who use them. Professionals who have a good grounding in the fundamentals of test equipment are better prepared for the challenges they meet while dealing with electricity. Found in most toolboxes, a clamp meter, as well as the other types of test equipment, raises an array of questions connected with its structure and operating principles
What's a Clamp Meter? |
A clamp meter is a testing device used for measuring current in a non-contact way. The technology enables users to conduct measurements without breaking the circuit, as well as to measure high current. In contrast to well-known multimeters, clamp meters allow taking readings without powering down the equipment you are measuring. These devices provide a comparatively high level of safety, as no direct contact with the current is needed.
Although the first clamp meters were designed to take AC readings only, modern clamp multimeters are able to measure both alternating and direct current as well as AC/DC voltage, resistance, continuity, temperature, capacitance, and more.
Clamp meters come in various form factors and designs but their operating principles are similar. The simplest clamp meter consists of a display, trigger, rotary switch, functional buttons, and jaws (Picture 1). Whilst the functions of the separate details are more or less clear, the operating principles of the instrument may raise some questions.
How Does a Clamp Meter Work? |
Inside the plastic housing, the current-sensing jaws of a current transformer have a magnetic core that measures the magnetic field of the current flowing through a conductor. Then, it converts those measurements to AC readings, which you can see on the display.
For those who know the difference between AC and DC current, it is questionable whether a clamp meter can measure DC current as well. The answer is simple - yes.
Flowing through a conductor, the direct current has a zero frequency, or simply put, it creates no magnetic field. So it becomes impossible for a current transformer to measure DC. Here is where the hall-effect sensor comes in handy. Having a completely different structure, this meter is able to measure both alternating and direct current.
How to Use? |
Having learned the principles a clamp meter works on, it’s time to find out how to use it.
Before the procedure
Before taking measurements, you should read the manual attentively. All clamp meters are quite similar in their design but still can have some differences, depending on the brand, model, configuration, and the functions they can perform.
Here you can see the model of the most common digital clamp multimeter, popular among professionals and DIYers alike (Picture 2).
Let’s examine it attentively and pay attention to some important details:
1. Measurement ranges.
Looking at our meter, we can observe a marking, just below the transformer jaws (Picture 3). This actuallyinforms us about the voltage and current range the device is capable of measuring.
- this symbol means that the device measures both direct and alternating current, whereas the CAT II sign - is its overvoltage installation category, that informs users that it can be used for the following applications:
- Equipment in fixed installations, such as switchgear and polyphase motors;
- Bus and feeder in industrial plants;
- Feeders and short branch circuits, distribution panel devices;
- Lighting systems in larger buildings;
- Appliance outlets with short connections to a service entrance, and more.
As we can see, our multimeter can measure both DC and AC circuits with up to 600V and 400A.
Warning! To avoid harms and damages to your device, do not attempt to measure voltages that exceed allowed ranges.
2. Rotary switch positions. The marking around the rotary switch show measurements the device is designed to take. Look through the chart below to find out the meaning of the symbols you may see on your clamp meter.
This very clamp multimeter is capable of measuring voltage, resistance, and current as well as testing continuity (Picture 4).
Warning! Manufacturers are free to print their own symbols on the tools. Study the manual attentively to eliminate the possible risks.
3. Buttons. Buttons can perform various functions, from turning on/off the device to switching between the modes (Picture 5).
Our meter has three functional buttons:
- Select - to select alternate functions;- to disable the Sleep Mode;
- Relative - to switch between different modes;
- Relative - to switch between different modes;
Relative - to switch between different modes;To learn more about the function of each button of your meter, please read the manual.
Having examined the device, now we are ready to conduct measurements.
Warning! Do not use your meter if the case, insulation, or other parts of your device are damaged.
During the procedure
Measuring current with a clamp meter is simple. You should switch to the required current measurement range, press the trigger to open the jaws, place the conductor under test inside, and close the jaws. The display will show the measurement results (Picture 6).
Warning! Although most clamp meters have similar operating principles, check with the instruction manual to take the specific device features into consideration.
There are some important things to remember while using a clamp meter:
Clench exactly the conductor that you need to measure. Basically, wires consist of two or more separate conductors inside the isolation. Thus, measuring the whole cable at a time, we will get a zero result as the meter will detect the difference between the currents.
So, if you have a cable consisting of several wires and you need to measure one of them, you have to strip it or find a place where the cable is divided into separate wires (Picture 7).
Set the correct measurement range. Sometimes users happen to doubt what measurement range to choose. In this case, you have to start with the maximum range and then switch to a lower range if needed (Picture 8). This will eliminate the risks.
As we have discovered earlier, our device is actually a clamp multimeter that is capable of measuring amps, ohms, and volts.
Measuring resistance and voltage or testing continuity with a clamp meter is almost the same as with an ordinary multimeter.
All it takes is to plug in the measuring probes, choose the correct mode, and connect the leads to the circuit you need to measure. In our case, we are measuring resistance (Picture 9).
How to Choose? |
Choosing a multimeter, decide whether you need a multifunctional device that is capable of measuring voltage, resistance, temperature, and more or a simple tool for measuring current only. Consider the functions it is designed to perform as well as its measurement ranges, and choose the most suitable variant from an extensive variety of top-notch meters from the industry-leading brands at Prime Buy!
