Multimeter notes: Difference between revisions
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Not a standard feature, because it needs some faster processing to do. | Not a standard feature, because it needs some faster processing to do. | ||
There are a few methods | There are a few methods | ||
https://electronics.stackexchange.com/questions/441383/how-do-digital-multimeters-measure-capacitance | https://electronics.stackexchange.com/questions/441383/how-do-digital-multimeters-measure-capacitance | ||
One way would be to charge it, and monitor the voltage. | |||
t=RC, so with a known resistance, | |||
At ''very'' low capacitance you are instead limited by measuring speed/precision. | |||
Some multimeters refuse to go down to picoFarad, | |||
probably also for the reason that by then you're also measuring the wires and even the meter's PCB, | |||
so even if the value shown is accurate we shouldn't pretend it is necessarily all that meaningful. | |||
Limitations: | |||
However, '''the larger the capacitance, the longer it would take to get to the actual would take''' | |||
: At low capacitances we would call that rise time, but if you use the same resistor for millifarads or larger you're looking at minutes or hours to get a reasonable charge | |||
Multimeters may do that, but with a fixed current to make life easier. | |||
They also use a fixed time, rather than waiting for the RC. | |||
That ''does'' limit the precision, | |||
but also it doesn't spend that much of the battery. | |||
If you want an answer ''quick'', you start looking at expensive RLC meters. | |||
If you can accept a slower answer you can do it much cheaper. | |||
https://www.circuitbasics.com/how-to-make-an-arduino-capacitance-meter/ | |||
You can even do a chirp and see what kind of filter it's being, | |||
but this doesn't seem like it's precise without taking more time either. | |||
In-circuit, they will tend to measure the largest capacitance, which is only sometimes the capacitor you're holding it to. | In-circuit, they will tend to measure the largest capacitance, which is only sometimes the capacitor you're holding it to. | ||
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