Author Topic: Capacitor leakage tester/ checker  (Read 7218 times)

0 Members and 1 Guest are viewing this topic.

Offline diydidi

  • Contributor
  • Posts: 19
Capacitor leakage tester/ checker
« on: November 01, 2016, 06:01:39 pm »
Hi
I want to build a capacitor leakage tester/ checker instead of buying something expensive.
I was thinking of using my variac, followed by a voltage doubler to reach about 700V DC.
I'm not sure how to do the metering. I could either use a 50uA moving meter in series with a 10k resistor followed by the cap under test, or I could measure the voltage across the cap instead of the uA meter keeping the series 10K resistor.
I'm open for ideas and if any one has a better layout, please share it with me.
Thank you!
 

Offline Seekonk

  • Super Contributor
  • ***
  • Posts: 1849
  • Country: us
Re: Capacitor leakage tester/ checker
« Reply #1 on: November 01, 2016, 06:19:10 pm »
I built a MOV tester for production and used a 120V isolated winding of a transformer and a quadrupler or more to get a high enough voltage at very low limited current.  I can see driving a 12V winding pulse width to get the desired voltage you want.  Use a resistor to measure the current, protected by the voltage drop of two diodes in parallel. This will limit the maximum voltage of your sense circuit. Feed that into an op amp that drives your meter.
 

Offline Fraser

  • Super Contributor
  • ***
  • Posts: 9438
  • Country: gb
Re: Capacitor leakage tester/ checker
« Reply #2 on: November 01, 2016, 06:21:33 pm »
Your proposed design sounds dangerous.

A Safer option would be to repurpose a much safer and cheap CCFL or EL driver board to create your 700V DC. Current monitoring may be a suitable ammeter but I would opt for p.d across a series resistor so that an oscilloscope may be used to monitor any momentary leakage.

Some thought is needed for circuits protecting the Multimeter or Oscilloscpoe from a damaging high voltage event.

Fraser
« Last Edit: November 01, 2016, 07:52:44 pm by Fraser »
 

Offline kripton2035

  • Super Contributor
  • ***
  • Posts: 1901
  • Country: fr
    • kripton2035 schematics repository

Online Ian.M

  • Super Contributor
  • ***
  • Posts: 8597
Re: Capacitor leakage tester/ checker
« Reply #4 on: November 01, 2016, 07:07:51 pm »
Another key area that you have to get right is quickly and effectively discharging the capacitor under test at the end of the test, and reliably indicating it has discharged to a safe voltage.
 

Online Johnny10

  • Frequent Contributor
  • **
  • Posts: 694
  • Country: us
Re: Capacitor leakage tester/ checker
« Reply #5 on: November 05, 2016, 10:06:09 am »
I know your interest is in building your own... but I have restored one of the Heathkit IT-28 Cap and leak detector. They are very inexpensive. Work great. Checks Leakage to 600 volt.
http://www.ebay.com/itm/Heathkit-IT-28-Capacitor-Checker-/201681713037?hash=item2ef52ab78d:g:5zgAAOSw8w1X8Yua

Also schematic easy to find.
Or use for parts.
« Last Edit: November 05, 2016, 05:47:47 pm by Johnny10 »
Tektronix TDS7104, DMM4050, HP 3561A, HP 35665, Tek 2465A, HP8903B, DSA602A, Tek 7854, 7834, HP3457A, Tek 575, 576, 577 Curve Tracers, Datron 4000, Datron 4000A, uTracer, HP5335A, EIP534B 20GHz Frequency Counter, TrueTime Rubidium, Sencore LC102, Tek TG506, TG501, SG503, HP 8568B
 

Offline PA4TIM

  • Super Contributor
  • ***
  • Posts: 1123
  • Country: nl
  • instruments are like rabbits, they multiply fast
    • PA4TIMs shelter for orphan measurement stuff
Re: Capacitor leakage tester/ checker
« Reply #6 on: November 05, 2016, 05:33:19 pm »
http://www.pa4tim.nl/?p=1385
A variac is not a great Idea because of safety.
I made a page about DC leakage, there are also a few schematics. They are very easy to make. 
For voltage over 450V I use an old HP PSU  that was made for photomultipliers but you can use a transformer like they used in tube equiped stuff. Because we have 230VAC and 450VDC  is more then enough for me I used two transformers with the secundairs coupled.
www.pa4tim.nl my collection measurement gear and experiments Also lots of info about network analyse
www.schneiderelectronicsrepair.nl  repair of test and calibration equipment
https://www.youtube.com/user/pa4tim my youtube channel
 

Offline kripton2035

  • Super Contributor
  • ***
  • Posts: 1901
  • Country: fr
    • kripton2035 schematics repository
Re: Capacitor leakage tester/ checker
« Reply #7 on: November 05, 2016, 05:57:03 pm »
siliconchip made a capacitor tester and reformer
http://archive.siliconchip.com.au/cms/A_112073/article.html


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf