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Capacitor tester in circuit

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Well, that's invalid too! Your capacitance meter is on the 2000μF range, so either that's a faulty capacitor or your meter does strange things when over range. If it is a 4700uF capacitor then it's measuring 4200μF.

So is it 4700μF, 425μF, or 4200μF? You need (at least) your capacitance meter to roughly agree with your capacitor before you can make any sense from the output of your tester.

Do you understand why I said the test with the 10,000μF capacitor was invalid? And why this one is too?
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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This is protection against charged capacitors.
There may be 2 diodes or 4.
View attachment 43666

So that's yet another option. Is that how it is wired?

Why not use a single diode in each direction?

Can you update the schematic to show the correct wiring?
 

caps

Jul 29, 2018
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Well, that's invalid too! Your capacitance meter is on the 2000μF range, so either that's a faulty capacitor or your meter does strange things when over range.
There is no 2000uF range.
The range is 10000 uF.
The small division is 200uF.
1v-1000uF
2v-2000uF
3v-3000uF
4v-4000uF
5v-5000uF
6v-6000uF
7v-7000uF
8v-8000uF
9v-9000uF
10v-10000uF
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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There is no 2000uF range.

I was referring to your capacitance meter. But on a desktop monitor I now see that the range is 2000uF x10 (on which the 4700uF capacitor measures 425uF)

10v-10000uF

But your circuit is powered from a 9V rail!!!!
 

caps

Jul 29, 2018
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I was referring to your capacitance meter. But on a desktop monitor I now see that the range is 2000uF x10 (on which the 4700uF capacitor measures 425uF)
There is no range of 2000uF and can not be.
Capacitor tester.jpg Capacitor tester (2).jpg
 
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caps

Jul 29, 2018
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Why not use a single diode in each direction?
Yes.2 diode in parallel.
Protection (2).jpg
Small capacitors.
Scale 1000pF.
Capacitor 1000pF 5%.
Scale 0,1uF.
Capacitor 0,014uF 0,5%.
 

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(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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There is no range of 2000uF and can not be.

FFS! Look at this post (the second image).


We will use only the 0-10v scale of the Chinese tester. This has nothing to do with the 9v power supply.

It has everything to do with your 9V power supply. How can you call it a (say) 1000μF range when the absolute highest it can read is 900μF?
 
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caps

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I no longer know how to explain to you.
Look here. Capacitor 680uF.
We select the range 1000uF.
We measure the capacitance-690uF.
We select the range of 10000uF. If the tester works correctly, there should be a multiplicity of measurements on all ranges.
We measure the capacitance-690uF.
 

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(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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First issue: I'm talking about your other capacitance meter.

It shows you measuring a 4700uF capacitor on it's 20,000 uF range and reading 425uF on it's digital readout.

This cap must be faulty and isn't a good unit to use to compare with your meter.

Second issue: when set to your 1000uF range on your home built tester, the maximum it can measure is 900uF.

1000uF is the full scale for your voltmeter on the 10V range. It would be better to call it the x100uF range, since the output in volts, if multiplied by 100 is the capacitance in uF.

Why not have a higher supply voltage so it can output 10V (even better, 11V or 12V to give it some overhead)?
 

caps

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*steve*
"It shows you measuring a 4700uF capacitor on it's 20,000 uF range and reading 425uF on it's digital readout."
This is a 3 1/2 capacitance meter. In the range of 20000uF, the reading is correct-4250uF.
"This cap must be faulty and isn't a good unit to use to compare with your meter."
No, this is a new capacitor.
"Second issue: when set to your 1000uF range on your home built tester, the maximum it can measure is 900uF."
No. It can measure 1000uF. Just that capacitor has a capacitance of 900uF.
"1000uF is the full scale for your voltmeter on the 10V range. It would be better to call it the x100uF range, since the output in volts, if multiplied by 100 is the capacitance in uF."
For this there is a switch 1uFx1000.
"Why not have a higher supply voltage so it can output 10V (even better, 11V or 12V to give it some overhead)?"
The circuit elements are designed to work correctly when powered 9v.
1000uF-50v.
 

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(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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No. It can measure 1000uF. Just that capacitor has a capacitance of 900uF.

How can it output 10V when the power supply is 9V?
 

caps

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Yes, I just marked the scale of 10v, so that it was clear on what scale the reading is going on. There are several scales.
The output of my tester is connected to the measuring part of the Chinese tester.
YX360-TR.jpg
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Well, that makes more sense. I had assumed you were using a multimeter.
 

davenn

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Yes, I just marked the scale of 10v, so that it was clear on what scale the reading is going on. There are several scales.
The output of my tester is connected to the measuring part of the Chinese tester.
View attachment 43726

photo is way too small for me to see anything useful
 

caps

Jul 29, 2018
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Made new test leads.
A thin, flexible cable is connected to the tweezers. Now it is very convenient to work with one hand.
Large-sized film capacitors and smd capacitors are easily measured.
 

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caps

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Capacitor SMD 220uF.
Range 1000uF.
Film capacitor 1uF.
Range 1uF.
Bad capacitor 470uF 25v.
Range 100uF.
 

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caps

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A 47uF 400v capacitor is connected in parallel to one of the windings of a pulse transformer. The inductance of this winding is 650uH.
The measurement result is completely correct-44uF.
 

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