In this paper, how to measure the current and the small make up to digital multimeter introduces digital multimeter to measure current often make mistakes, if you want to understand the details of the digital multimeter, or want to enhance the understanding of digital multimeter, might as well look at the following content.

A, digital multimeter

First of all, let's take a look at the basic content of digital multimeter. Digital multimeter is a kind of multi-functional electronic measuring instrument, usually contains ammeter, voltmeter, ohmmeter, and other functions, is sometimes called a multimeter.

Digital multimeter is suitable for portable equipment for the basic fault diagnosis, and the worktable are placed with equipment, some equipment for the resolution of seven or eight digit figures.

Digital multimeter functions by converter, A/D converter, LCD display (LCD), power and function/range switch, etc. Usually adopt A/D converter ICL7106 double integral A/D converter. Using ICL7106 integral model, two for the first time integral of the input analog signals V1 is called sampling process; Reference voltage - VEF integral process called comparison process, which is the second integral. The two integral process by a binary counter counts, converted to digital quantity, and displayed in digital form. To measure ac voltage, current, resistance, capacitance, diode is the pressure drop, transistor amplification coefficient and other power, must add a corresponding converter, with the measured power is converted into a dc voltage signal.

Furthermore, we also know that the digital multimeter is used for measurement of the electrical electronic instrument. Digital multimeter has many other special features, but the main function of the digital multimeter is measuring voltage, resistance and current. Then, the digital multimeter is mainly used in what areas? Digital multimeter, as a modern multi-functional electronic measurement instruments, mainly used in the physical, electrical and electronic measurement field, etc.

B, the digital multimeter measuring current

So, how, when using the digital multimeter to measure the current in the circuit? Digital multimeter to measure current, general need five steps, the step five steps in detail as follows:

1) disconnect the power supply circuit, in order to make all the high voltage capacitor in the discharge state, the aim is to insert a multimeter probe provides a location

2) in the second step, we need according to the specific requirements, and refer to the manual product choose ac or dc gear. Insert the black probe COM input jack. Then, according to our expectations may read value, insert the red test probe amp or ma input jack.

3) if you use A terminal, then set the rotary switch in the mA/A position. If you use mA/mu A terminal, then set the rotary switch in mu A position or mA/A position. Connect the probe tip to disconnect point at both ends, all current flows through the digital multimeter.

4) then, reconnect the power supply circuit and reads the display value

5) closed circuit power, and to all high voltage capacitor discharge. Unplug the multimeter wiring, make the circuit back to normal working condition.

C, digital multimeter measure current common errors

The above five steps are usually adopt digital multimeter measurement used in the current process, although a lot of friends in accordance with the above steps can complete measurement work well, but there are still a few friends will make some mistakes in the process of measurement. A common mistake is to insert the test line current jack and try to test voltage. The small resistance in digital multimeter can lead to short circuit voltage sources. If large current flows through the digital multimeter, if the multimeter is not fully protected, will not only damage the instrument and circuit, will also hurt the operator. If it is a high voltage circuit, will cause the bigger danger.

Therefore, digital multimeter should have big enough current input protection fuse. No current input fuse instrument cannot be used in high energy circuit (> 240 v alternating current). To use the fuse tube digital multimeter, fuse tube should have enough capacity.

Eliminate the high-energy fault. Fuse rated voltage of the maximum voltage should be greater than you expected. Multimeter measuring 480 v circuit, 20 a, 250 v fuse can't protect. Multimeter measuring 480 v circuit, only 20. A, 600 v can fuse protection.