Measure the capacitance ratio of two capacitors, the capacitance is in microfarads

davidzhu210

Measure the capacitance ratio of two capacitors, the capacitance is in microfarads [Copy link]

 

I want to measure the ratio of the capacitance of two capacitors. For example, C1=100uF, C2=22uF, and the output voltage value must be 100/22=4.55V. The capacitance range is 1uF~220uF, and it is implemented with discrete component circuits without a single-chip microcomputer. Can you please give me some ideas?

杨鹏飞

I don't understand, I just came here to support

Jacktang

Want to know the meaning of measuring the ratio of the capacitance of two capacitors

That environment requires

maychang

[Implemented with discrete component circuits, without a single-chip microcomputer]

Using discrete component circuits means that integrated circuits cannot be used, that is, integrated operational amplifiers cannot be used. Although we cannot say that this is impossible, it requires a lot of carefully selected diodes, transistors, resistors, capacitors... Each component must be measured. Can you afford such a cost?

maychang

[It is realized by discrete component circuit, without single chip microcomputer. ]

Such a circuit can be realized, but what is the point?

captz

It is easy to measure for the sake of measuring. But what is the point and what is the use?

吾妻思萌

This kind of tiny detection is difficult, and the detection error is large. The Huygens bridge method seems to be very common, and the manufacturer's small capacitor tol is 30%.

captz

Ratio is not "V"

Honghuzaitian

Jacktang posted on 2022-10-30 08:24 I want to know what kind of environment is needed to measure the ratio of the capacitance values of two capacitors

I am also curious about the significance of this measurement. Is it something from a textbook? Because in reality, it is cheaper and easier to use other methods.

qwqwqw2088

Do I need to measure the capacitance ratio circuit, and also require the output voltage value to be 100/22=4.55V?

davidzhu210

This is a circuit that needs to measure the capacitance ratio

maychang

davidzhu210 posted on 2022-10-30 17:59 This is a circuit that needs to measure the capacitance ratio

To measure the ratio of two capacitors, you only need to connect the two capacitors in series, pass a certain AC current, obtain the voltages on the two capacitors respectively, and then do a division.

But if we are limited to using discrete components and cannot even use op amps, that would be quite troublesome.

captz

maychang published on 2022-10-30 18:07 To measure the ratio of two capacitors, you only need to connect two capacitors in series, pass a certain AC current, obtain the voltage on the two capacitors respectively, and then do a division...

This is the simplest and most effective method.

davidzhu210

Can use op amps and integrated chips

captz

Squeeze toothpaste.

Then use a divider chip and a voltmeter.

maychang

davidzhu210 posted on 2022-10-30 17:59 This is a circuit that needs to measure the capacitance ratio

In fact, the universal bridge that can measure capacitance and inductance is essentially measuring the ratio of two capacitors when measuring capacitance, except that one of the two capacitors is a standard capacitor, and the measurement result is the ratio of the capacitance to be measured to the standard capacitance. This ratio is determined by the resistance values of the other two arms when the bridge is balanced. The LCR bridge that can be purchased on the market to measure capacitance is just an automatic change instead of the manual change of the bridge arm resistance value, and it still measures the ratio of the capacitance to be measured to the standard capacitance.

jiangbianyeren

Watching, watching and learning, asking the old engineer to lead the way, the new classmate Mark

davidzhu210

Thank you for the help from the great god above!!

chunyang

What the OP mentioned is too broad. You should at least talk about what instruments can be used to measure it...