How to adjust the current of a digital multimeter? 5

1. Digital multimeter.

The measurement principle of the current level is measured using the U=IR formula method.

As can be seen from the formula, when the input current i, a voltage drop u is generated on r and passes through the meter header.

The circuit is displayed on a liquid crystal.

When i is constant, the display value u can be changed by changing the value of r.

2. For ordinary digital multimeters, the full-scale value of the general meter head is 200mV, from which the value of R can be calculated, and the value of R is 1 ohm when the 200mA file is used; 100 euros in the 2ma range; 20A (10A) is in Europe.

3. The method of positioning R, for example, to find the resistance R of 2mA, you can dial the range to DC 2mA file, in the other multimeter 200 ohm file, at its input end, you can measure the resistance value of 100 ohms, this is the R, disassemble the instrument, check the wiring of the instrument, you can easily find it, and enter the resistance in series on it, which can increase the display value; Resistors on top of it to reduce the displayed value.

1. First of all, we must test each multimeter and analyze whether the indication deviation of several current levels is in one direction? Is the deviation ratio consistent? 2. If the deviation ratio is within your allowable range, you can adjust the shunt resistance, 3. If the current indication is small, it is

The method is to apply solder to the shunt wire with a soldering iron. If the current indication is too large: the method is to file the shunt wire.

4. If the current deviation of each gear is not in the same direction, and the error is beyond your allowable range, you need to adjust the resistance of each gear separately.

A digital multimeter is a relatively simple measuring instrument. In this article, the author will teach you the correct way to use a digital multimeter. Start with the measurement methods of voltage, resistance, current, diode, transistor, MOS FET and other measurement methods of the digital multimeter, so that you can better grasp the measurement methods of the multimeter.

Before use, you should carefully read the relevant instruction manuals and be familiar with the functions of power switches, range switches, jacks, and special sockets.

Put the ON OFF switch to the ON position, check the 9V battery, if the battery voltage is insufficient, it will be displayed on the display, then the battery needs to be replaced. If your display doesn't show up, follow these steps.

The symbol next to the test pen jack indicates that the input voltage or current should not exceed the indicated value, which is to protect the internal wiring from damage.

Before the test. The function switch should be set to your desired range.

Digital multimeters are displayed in numbers.

parameter value. Figure 9-11 shows the general outline of the digital multi-purpose return table. The DMM has a clear and intuitive display, stable performance, and high sensitivity and accuracy. Here's how to use it:

Figure 9-11 Digital multimeter.

When measuring DC current with a digital multimeter, first insert the black watch pen into the "com" hole, when the measured current is greater than 200mA, the red watch pen should be inserted into the "10A" jack, and turn the knob to the DC "10A" block; When the current to be measured is less than 200mA, insert the red watch pen into the "200mA" jack and turn the knob to the appropriate range within "200mA" DC.

Once the range is selected, the multimeter is threaded into the circuit and the reading is made when it is stable. If the value on the screen is "1", the range should be increased and then measured; If there is a "—" on the left side of the value, it means that the current flows from the black pen to the multimeter, and the two pen pens can be swapped. When measuring AC voltage with a digital multimeter, the gear should be hit to the AC block, and the connection method is the same as measuring DC voltage.

Here's how to use it:

Let's take a look first. 2.In the resistance mode, the red pen is inserted in the V socket and the black watch pen is inserted in the COM socket. Measure both ends of a circuit or device.

It must not be electrified, otherwise the multimeter will be burned out. ）

3.DC voltage level, the same resistance level measurement method.

4.AC voltage range, the same resistance level measurement method.

5.AC current setting, red pen plugged in MA or 10A socket, black pen plugged in COM socket. String a multimeter into the circuit for measurement.

6.DC current gear, red pen plugged into MA or 10A socket, black gauge pen plugged into COM socket. String a multimeter into the circuit for measurement.

7.Diode level, same resistance level measurement.

1: Measure the diode, such as the multimeter shows 1, exchange the meter pen to measure again, then the multimeter shows a few tenths of a day, indicating that the diode is good. This value is the positive pressure drop of the tube.

Silicon around, germanium material around. If the two measurements are the same, then the tube is bad.

2. Measure the on-off or short-circuit of the line. If there is a short circuit or path, the buzzer emits a sound.

Note: During the use of the multimeter, you should not touch the metal part of the watch pen with your hands, so that on the one hand, you can ensure the accuracy of the measurement, and on the other hand, you can also ensure personal safety.

It is not possible to shift gears at the same time as the measurement, especially when measuring high voltages or currents. Otherwise, the multimeter will be destroyed. If you need to change gears, you should disconnect the watch pen first, and then go to measure after changing gears.

Be sure to estimate the measured value before measuring, if you can't estimate it, start with the maximum gear and then decrease the gear measurement.

After use, turn the gear knob to the highest voltage to prevent the next use, the gear is incorrect and damages the multimeter. and turn off the power.

If it is found that the reading of the modified meter is higher than the reading of the standard meter, to reach the value of the standard meter, the shunt resistance of the modified meter should be adjusted smaller, and the shunt resistance should be smaller, and the current of the shunt will be more, so that the current of the "high" part will pass through the shunt resistor, and the current through the meter head will be reduced.

According to the principle of parallel circuit current shunt, it can be seen that the resistance of your parallel connection should be appropriately adjusted to reduce the current flowing through the ammeter.

The results of the calibration give the absolute error of each scale of the meter. The largest absolute error is selected, divided by the range, and defined as the nominal error of the meter. According to the size of the calibration error, the accuracy level of the meter to be checked can be determined.

If the calibration error is between to and to, the table is graded.