What is a clamp meter? As its name suggests, it is shaped like a pliers and functions like a multimeter. It is one of the tools commonly used by electricians. The clamp meter is an abbreviation of the clamp ammeter. It is a portable measuring instrument that can directly measure the AC current of the circuit without disconnecting the circuit. Because it has a clamp-shaped movable opening in its shape, it is called a clamp ammeter. Generally, the clamp meter does not have the AC/DC voltage of 1kV or above. It is recommended not to measure the parameter above this voltage to avoid personal electric shock.
The first method for the use of the clamp meter is to require the two power cords to be separated, and the strands cannot be tested. At the same time, we can see that there are generally three jacks on the clamp multimeter. 1. VΩ is the jack for measuring the voltage resistance. Generally, the red test pen is inserted; 2. COM is a common test hole for each gear position, generally inserting a black test pen; 3. The partial clamp meter also has a hole with a lightning symbol, which is a hole for detecting the fire line, that is, inserting the red test pen The hole, the black test pen is not connected to the multimeter, and the lightning bolt symbol position of the turntable is dialed, and the charged body can be measured with the red test lead.
The figure below is an illustration of the use of the clamp meter. We will also explain it in detail below.
Diagram of the use of the clamp meter The use of the clamp multimeter's gear position, jack use, and range selection are all important. Let's take the FLUKE 337 as an example to detail the method of testing the AC current using a clamp ammeter.
1) Correctly select the gear position of the clamp meter, as shown in the figure, select AC AC current file
2) Open the clamp meter jaw and connect the clamp meter to the circuit under test.
The access method shown in the figure below is wrong, so that the current consumption of the circuit cannot be measured, but the leakage current of the circuit is normally zero.
3) Open the clamp meter jaws and correctly connect the clamp meter to the circuit under test. At this point, the actual current of the household appliance can be measured.
The access method shown in the figure below is correct. Only the single power cable of the circuit under test can pass through the jaws. Two wires can be tested separately. The measured values should be equal in theory, otherwise the line is not normal. The leakage current is large. The measured current value of the test circuit shown in the figure is 4.5A.
4) To test the starting current of the household appliance, press the “INRUSH” button on the basis of the previous step and then start the household appliance. The button process is as shown in the figure.
5) When the “INRUSH” button is pressed and the home appliance is still not activated, the meter displays as shown.
6) After starting the household appliance, the measured starting current is as shown below.
Analysis of the main points of the use of the clamp multimeter When in use, turn the range switch to the appropriate current position. Hold the watch body and press the switch with your thumb to open the jaws and introduce the wire under test into the center of the core. Then, when the switch is released, the iron core is automatically closed, and the current of the wire to be tested generates an alternating magnetic field line in the iron core, and the current value is reflected on the meter, which can be directly read.
1 Read the instruction manual carefully before using the digital multimeter to familiarize yourself with the power switch function and the limit switch, input jack, socket, and various function keys, knobs, and accessories. In addition, you should also understand the limit parameters of the multimeter, the characteristics of overload display, polarity display, low voltage display and other indicator display and alarm, and grasp the change rule of the decimal point position. Before the measurement, the test pen should be carefully checked for cracks, the insulation of the lead wire is damaged, and the position of the test pen is inserted to ensure the safety of the operator.
2 Before each measurement, check whether the measurement item and the limit switch are dialed, and whether the input jack (or dedicated jack) is selected.
3 When the meter is just measuring, the number of hops will appear. Wait until the displayed value is stable before reading.
4 Although the digital multimeter has a relatively complete protection circuit inside, it is still necessary to avoid operational malfunctions, such as using a current block to measure the voltage, using an electrical block to measure the voltage or current, and using a capacitive block to measure the charged capacitor. Etc., so as not to damage the meter.
5 If only the highest digit displays the number "1", the other bits are blanked to prove that the meter has been overloaded, and a higher limit should be selected.
6 It is forbidden to toggle the limit switch when measuring voltage above 10OV or current above 0.5A to avoid arcing and burn the contacts of the transfer switch.
7 Indicate the number of the hazard symbol next to the input jack, which represents the limit voltage or current input to the jack. Once it is exceeded, it may damage the instrument and even endanger the safety of the operator.
8 Clamp-type multimeter must not measure the current of the high-voltage line. The voltage of the tested line should not exceed the voltage level specified by the clamp meter (usually more than 500 volts) to prevent insulation breakdown and personal electric shock.
9 Measurement should estimate the magnitude of the measured current, select the appropriate range, and do not use small range to measure large current.
10 Before measuring, please pay attention to the range switch to the corresponding AC current gear. You can't use the voltage and resistance files to measure the current. Remember! Never use the resistance gear and current gear to measure the voltage. Otherwise, if you accidentally, the meter will be burned.
• Only one wire can be clamped per measurement. The measurement should be placed in the center of the jaws to improve the accuracy of the measurement. It is best to flatten the body with your hand to prevent the wires from leaning against the jaws and the body.
• After the measurement is completed, the range switch must be turned to the maximum voltage range position and then the power switch is turned off. To ensure the next safe use.
