What frequency does Victor vc97 multimeter test capacitors?

[electronium]

greeting to the forum users
at what frequency does the vc97 multimeter capacitor check the capacity of capacitors?

 

[danadak]

Probably a RC charge time measurement ? So no frequency per se. Unlike
the ESR measuring meters which do so at a freq.

Put a cap on it and look at waveform with a scope to confirm.

 

[crutschow]

It likely uses a constant-current to the capacitor and measures the time it takes to reach a specific voltage.

 

[danadak]

From Chatgpt -

low cost voltmeters how do they measure capacitance


Low-cost voltmeters measure capacitance using a few basic methods, typically relying on charging and discharging cycles of the capacitor. Here are the common methods used:

1. RC Time Constant Method​

This method measures the time it takes to charge or discharge a capacitor through a resistor. The voltmeter applies a known voltage to the capacitor through a resistor and measures the time it takes for the capacitor to charge to a certain voltage level. The capacitance CCC can be calculated using the formula:C=tRln⁡(VfinalVinitial)C = \frac{t}{R \ln\left(\frac{V_{\text{final}}}{V_{\text{initial}}}\right)}C=Rln(VinitialVfinal)twhere:

• ttt is the time taken to reach a certain voltage,
• RRR is the resistance,
• VfinalV_{\text{final}}Vfinal and VinitialV_{\text{initial}}Vinitial are the final and initial voltages, respectively.

2. Oscillator Frequency Method​

In this method, the capacitor is part of an oscillator circuit (like a Colpitts oscillator). The frequency of oscillation depends on the capacitance. The voltmeter measures the frequency of oscillation and calculates the capacitance using a known relationship between frequency and capacitance:f=12πLCf = \frac{1}{2 \pi \sqrt{LC}}f=2πLC1where:

• fff is the frequency,
• LLL is the inductance of the inductor in the oscillator.

3. Bridge Method​

This method uses a bridge circuit, like a Wheatstone bridge, but adapted for measuring capacitance. The capacitor to be measured is placed in the bridge circuit, and the voltmeter detects the balance point. The capacitance is then calculated based on the bridge balance conditions.

Implementation in Low-Cost Voltmeters​

Low-cost digital multimeters (DMMs) use microcontrollers to perform these measurements. The typical process involves:

1. Charging the Capacitor: The microcontroller charges the capacitor through a known resistor.
2. Timing the Charge Cycle: The microcontroller uses an internal timer to measure the time it takes for the capacitor to reach a certain voltage.
3. Calculating Capacitance: The microcontroller calculates the capacitance based on the timing measurement and the known resistor value.

Some low-cost meters might use dedicated capacitance measurement chips that simplify the design process. These chips integrate the necessary circuits for performing the measurement and providing a digital output that the microcontroller can easily read.

Practical Considerations​

• Accuracy: Low-cost voltmeters might not be as accurate as high-end LCR meters, especially for very small or very large capacitances.
• Range: They usually have a limited range of capacitances they can measure, typically from a few picofarads (pF) to a few microfarads (µF).
• Calibration: Regular calibration can help maintain accuracy.

These methods allow even low-cost voltmeters to provide reasonably accurate capacitance measurements for general-purpose use.

end chatgpt ---------------------------------------------------------------------------------------

Low cost meters of course have a number of precision R's in them that can be
muxed for the purpose doing RC, timing.


Knight

 

[electronium]

I don't have an oscilloscope, but with the frequency meter module, I was able to measure the frequency of the capacitor section that was testing the capacitor with a capacity of 1uf 400v.

video tseting and analyze

 

[danadak]

Look at post # 2 for a PC based sound card oscilloscope :

[SOLVED] - Typical beginner microcontroller questions

Hi, I'm doing preliminary research/reading about using a microcontroller. I see I have a lot more to read before a lot of the fun of e.g. making LEDs blink, but still. The attached picture is if it helps to visualize the basic idea - it's a block diagram concept, not a complete circuit...

www.edaboard.com

and https://windowsreport.com/oscilloscope-software-pc-laptop/

Whatever you do build the PC sound input protection circuits to make sure you
dont hose your sound inputs.


Regards, Dana.