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Need help with ESR(?) meter

When I have encountered power supply problems in the past I have just replaced all the caps. I have wanted to get an in-circuit ESR meter but they either came as kits or were more than I wanted to pay. A while ago someone posted here that one could get a functional ESR meter from China for under $30. I hastily did a web search and found this:

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I ordered one and after several weeks it came today. I hadn't paid attention to the picture. The device came without any instructions. There is an EZ-insertion socket which as far as I can tell utilizes only three pins, say

1,2,3. The unit works fine for testing resistors connected either from 1-3 or 2-3 or 1-2. I wanted to test some capacitors in circuit so I cut a clip lead in half and connected the wire ends to pins 1-3. The device seems to read electrolytic capacitors as diodes but gives two uF readings which bear no relationship to the values written on the capacitors. For example, an 800uF cap might read 1.3v, 2.1uF.

I am hoping that someone in this group can shed some light on the device, specifically how it can be used to tell me which caps have to be replaced in some device.

Thanks.

Reply to
root
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They probably will not test devices very well while in the circuit. Not too many testers will do it either for all components.

There is not too much to the testers. Just hook a component to any of the 3 leads and press the button. Some times it may help to switch the leads around. This is especially true with some transistors that have lots of leakage..

You can start here with a youtube video.

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Reply to
Ralph Mowery

The Bob Parker ESR meter kit will test Electrolytic caps in circuit. We've been selling them since about 1999 and the kit has gone through a few updates since then. Not as inexpensive as the Chinese ones, but far better support and replacement parts are readily available...includes schematics!

I won't put the link to my web site catalog, but my email address is the same as the web site...

John :-#)#

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Reply to
John Robertson

** You need to test some known good electros from your parts stock to get a feel for how the meter is working. Do not expect to test capacitance with the cap still in circuit.

Using an ESR meter is much like using a DC voltmeter, the reading gives useful no information unless YOU know what it SHOULD be.

Comparison with a known good electros of the same uF and voltage rating is the best way to know what is normal. Ones that read a few times higher are suspect and any that read 10 times higher are fit only for the bin.

... Phil

Reply to
Phil Allison

** You need to test some known good electros from your parts stock to get a feel for how the meter is working. Do not expect to test capacitance with the cap still in circuit.

Using an ESR meter is much like using a DC voltmeter, the reading gives no useful information unless YOU know what it SHOULD be.

Comparison with a known good electro of the same uF and voltage rating is the best way to know what is normal. Ones that read a few times higher are suspect and any that read 10 times higher are fit only for the bin.

... Phil

Reply to
Phil Allison

First, was the capacitor discharged before the test.

Second, did you connect it, and then press the button to start the tests?

I have one that is similar, and it displays the capacitance and ESR for electrolytics. I also have the original Bob Parker, and a couple other cheap ESR meters that all give adequate readings.

Reply to
Michael A. Terrell

Funny things hapen to electrolytics when an injected sine wave goes negative w.r.t. the designated polarity every half cycle. That may fool your meter into thinking it is looking at a diode or giving you strange readings.

I use a capacitance bridge (General Radio 1611-A) that allows a D.C. polarizing voltage to be superimposed on the injected A.C. to keep electrolytics properly biased.

--
Paul Hovnanian     mailto:Paul@Hovnanian.com 
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Reply to
Paul Hovnanian P.E.

** Not relevant to modern ESR meters that inject a low current at a high frequency ( ie 100kHz) so the voltage across the cap is far too small to cause such effects.
** That is a vintage instrument (1950s) made to test electros that were around at the time - some of which may have changed value when a DC voltage was applied.

.... Phil

.... Phil

Reply to
Phil Allison

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