How To Use A Multimeter To Measure Capacitance And Its Working Principle

Is it normal? Today Xiaobian will teach you several ways to measure capacitance, in daily life and work, we have to check some small components, such as judging good or bad. This article will explain how to use a multimeter to detect capacitance, and some ways to use a multimeter

The First Method: Measurement With A Pointer Type Multimeter

Set the multimeter to Ohm;

Select the gear according to the capacitance size: the capacitor below 10pF can use the multimeter Rx10k gear; 10PF~0.01uF capacitor, can choose multimeter Rx1k gear:

Map the red probe of the multimeter to the negative electrode of the capacitor, and the black probe to the positive electrode of the capacitor. Check whether the capacitor is normal by changing the pointer

Under normal circumstances, if the multimeter pointer swings to the right to a certain value and then returns to the leftmost infinity, it indicates that the capacitor is intact: The capacity of the capacitor can also be estimated according to the pointer swing amplitude: the larger the capacitor, the longer the charging time, and the larger/slower the pointer swing amplitude.

If the multimeter pointer swings to the right or even to 0, the capacitor is damaged or broken down.

The Second Method: Measurement With A Digital Multimeter

1. Measurement OF Non-Polar Capacitance

If it is a non-polar capacitor, set the multimeter to the "" file to measure whether it is on or off. If the multimeter displays 1, it is normal. If the multimeter displays 0 or another number, the capacitor is damaged. Second, the measurement of polar capacitance

The polar electrolytic capacitor, its shell appears "bulging", "deformation" or "leakage" phenomenon, can directly judge the capacitor has been damaged; Capacitance file of digital multimeter can also be used to measure capacitance:

(1) According to the rated capacity marked by the capacitor, the multimeter is hit to the appropriate range:

(2) Insert the capacitor into the capacitor hole of the multimeter, and the capacity of the capacitor can be measured.

If the capacitance is within the rated range, it indicates that the capacitor is intact, otherwise the capacitor is damaged.

Measure With The Resistance Level OF A Digital Multimeter

Under normal circumstances, the capacitor below 1μF, use the multimeter Rx10k gear; 1uF~100uF capacitor, use multimeter Rx2k stop; Capacity greater than

100uF capacitor, with multimeter Rx200 stop detection: the pen is connected to the two poles of the capacitor, according to the reading and change of the multimeter (the principle is the same as the pointer multimeter), determine whether the capacitor is good or bad. Note: When the electrolytic capacitor is measured, because the electrolytic capacitor is polar, if the measured value does not change significantly, the probe should be replaced with the corresponding pin for multiple measurements.

Principle OF Measuring Capacitance Capacity With A Multimeter

The capacitance value is measured when the current changes with time when the capacitor is charged with a multimeter resistance, and the capacitance value is calculated by measuring the time when the switched capacitor reaches the selected end point with a stopwatch. First, the multimeter sets the resistance and adjusts the machinery and zeroes, and then connects the capacitor and tims to a point near ∞

service

i=i0e-t/T(T=RC)

C=t/{r0x[-In(i end /i0)]}.①

C=-t/{r0xIn[r0/(r0+r end)...②

Where t: the time (seconds) from the time the capacitor is switched on to the selected end point

r0: The central resistance value of the selected resistance file of the multimeter is multiplied by the rate of the file (for example, the central resistance value of the Rx10 file is multiplied by 10, that is, r0)

r end: The resistance value of the selected end point when the capacitor is charged. (Unit :Q)

i End: The full degree current value of the selected resistance of the multimeter, that is, the open circuit voltage value of the resistance file E divided by the central resistance value multiplied by the rate of the file. (Unit:

i0: capacitor charge end current point [i0=E/(r0+r end) (Unit :A) Select end point Method:

The capacitance value can be calculated by formula ② with a digital resistance scale line close to ∞. Or the first grid point of the voltage and current file is used as the end point, at this time, the formula ① is used to calculate (i end /i0=1/50 multimeters are generally 50 cells).

Note:

Discharge the short circuit before measurement and make sure the contact is good:

Electrolytic capacitors must be positively connected;

Reasonable selection of resistance gear makes the charging time larger and convenient for accurate timing;

Adjust electrical and mechanical zero positions before connecting capacitors;

Capacitors with voltages less than 12V cannot be measured with Rx10K.

Common Faults And Maintenance Methods OF Multimeter

Analog multimeter is one of the multimeters, so the things that can be measured are the same, the following through some introduction, talk about the common faults and maintenance methods of multimeters:

The Pointer Swing Is Not Normal, When The Pendulum Resistance

The solution:

(1) Open the case, use small tweezers and screwdriver to trim the mechanical swing part, so that the pointer swings flexibly; (2) re-weld the meter head line, reconnect the shunt resistance when it is disconnected, and change the shunt resistance of the same type when it is burned off; (3) Re-adjust the shape of the spring with tweezers, so that the outer ring is smooth and the layout is uniform :(4) trim the support part 2, the resistance file is not indicated

(1) Reassemble the multimeter battery, or replace it with a new battery;

(2) re-weld the connection, and adjust the potentiometer center contact plate so that it is in good contact with the resistance wire (3) wipe the contact oil, and trim the contact plate, if the welding connection line is disconnected, to re-brilliant connection,3, in the pen short circuit, the pointer is adjusted to zero, or the pointer swings back and forth is unstable (1) replace the same model of the new battery;

(2) Replace the series resistance; (3) Adjust the socket shrapnel so that it is in good contact, and remove the oxide layer on the meter plug and socket; (4) Clean the contact contact of the multimeter switch with alcohol, and correct the contact distance between the moving contact and the static contact sheet; (5) Press down the moving contact plate in the middle of the zeroing potentiometer with tweezers to make it in good contact with the static contact resistance wire,4, the resistance range is blocked or the error is too large

(1) Replace the resistance with the same resistance value and power;

(2) Wash and repair the bad contact with alcohol;

(3) Replace the stop shunt resistor;

(4) Replace the new battery of the same model;