note:

Do not measure live components during use, and discharge them before measuring capacitance!

If you accidentally measure the live parts, it will not work properly.

 Overview:

The LCR digital bridge is mainly used for accurately measuring the L, C, and R parameters of components, with wide measuring range and high precision. Playing the ore radio, most components require DIY and no nominal technical parameters. For example, it is necessary to know the reactance characteristics of devices such as resonant devices, detectors, antennas, earphones, and transformers. Among them, the high frequency parameter can solve the problem using the Q table, and the low frequency parameter Q table is difficult to measure. In order to solve this problem, the author believes that the LCR digital bridge can be competent.

·Design goals:

1, can accurately measure the L, C, R of the reactor, the accuracy is better than 0.5%, if the calibration is performed, the accuracy is better than 0.3%

2, easy to take, the circuit is simple, easy to make, the cost should be properly controlled. Make it have a stronger amateur DIY value and research value, and learn the details and principles of the LCR bridge through design and DIY.

·The basic characteristics of this LCR

Word count of AD converter: about 1000 words, using oversampling technology, effective resolution is about 4000 words

Measurement method: quasi-bridge measurement, the measurement principle is similar to the proportional method to measure resistance.

The main measurement range: 1 ohm to 0.5 mega ohm, accuracy 0.5% (theoretical), impedance comparison, no more than 0.3%

Effective measurement range: 2 milliohms to 10 megohms, minimum resolution of about 0.5-1 milliohm

Series residual error: less than 2 milliohms, this error can not be ignored in low resistance measurements

Parallel residual error: greater than 50M ohms, this error can not be ignored in high resistance measurements

Q value error: ±0.003 (Q<0.5), Q/300 (Q>2, relative error, simple algorithm), others estimated by about 0.5%

D value error: ±0.003 (D<0.5), D/300 (D>2, relative error, simple algorithm), others estimated by about 0.5%

Note: Q = 1/D

ESR error: |Z| / 300

In the high-resistance measurement, D and Q are effectively measured at a capacitance of 40 kPa or more @7.8 kHz, and D and Q accuracy is much worse than 20 pF.

Open circuit, short circuit clear: LCD version provides this function to facilitate high resistance and low resistance measurement. The LED version does not have this function, so the LED version of the small-capacity capacitor must be manually corrected to get the correct result.

Source amplitude: 200mV (100Hz), 180mV (1kHz), 190mV (7.8kHz)

Inductance: 0.02uH resolution, measuring range from 0.1uH to 1000H, not tested beyond 1000H (theoretically can also be measured normally).

Capacitance: The resolution is related to the fixture. If the fixture is good, it can effectively distinguish 0.05pF, and can only distinguish 0.1pF or even 1pF without shielding. The upper limit has not been tested. Only the 10000uF capacitor has been measured, and there is no larger capacitor on the hand.

  Recommended simple fixture: 7cm to 10cm long, 7.5 square millimeter wire, can be attached to a small clip.

The reference source of this table: 4 reference resistors, one time reference. The resistor reference is the four lower arm resistances of the bridge. The time reference is obtained with a 32MHz quartz crystal oscillator, and the accuracy can meet the requirements of the bridge.

Frequency accuracy: The actual frequency is 99.18 Hz, 999.45 Hz (another version 976.56 Hz), 7812.5 Hz, abbreviated as 100 Hz, 1 kHz, 7.8 kHz. Since the frequency resolution of the DDS is limited, the integer frequency is not used. The frequency accuracy is approximately 0.02% (determined by the quartz crystal oscillator circuit).

Signal source distortion: no special instrument test, only estimate. After performing high-pass filtering on the output signal, it was observed with an oscilloscope and no detectable distortion was found. If there is perceptible distortion, there is some impact on the D value measurement.

Packing List

1x host

1x insert clip

1x patch clip