Digital multimeter - how to solve  - Page 1
Forum section: electronics / beginners

author: Jane
author_rank: Frequent Contributor
timestamp: January 03, 2025, 10:35:37 am
content: I use a multimeter in diode mode ,during repair work, to test cappaitors for shorts. Because my work is microsoldering repair I must use microscope.When a cappacitor is shorted I can hear the voice from the multimeter.( in diode mode). Problem begins when a cappacitor is not fully shorted but only partly. Then the multimeter does not sound. To be sure that every cappacitor is good I must check the display of the multimeter, which is not good ( changing my view from the microscope to the multimeter and back and forth).Do you have any idea how to find out a partly shorted cappacitors without changing my eyes view from microscope?Thanks for ideas

author: Kleinstein
author_rank: Super Contributor
timestamp: January 03, 2025, 11:03:50 am
content: Partially shorted capacitors are rare. Often it is more of another part in parallel in the circuit.A reasonable solution would be to power the circuit and look at it with a thermal camera.

author: NE666
author_rank: Frequent Contributor
timestamp: January 03, 2025, 12:29:49 pm
content: I agree with the previous poster; wrong tool, incorrect test premise.However, if it works for your specific case and you're doing enough of it that using a regular multimeter resistance display is causing significant throughput issues, then I'd suggest replacing the multimeter with either a) one that has pass/fail threshold capability, with audio cues or b) a low-cost custom built something to achieve the same (perhaps a current source, with the voltage developed across the DUT being passed to a VCO, with audio output. Or a simple binary pass/fail tone).

author: jfiresto
author_rank: Frequent Contributor
timestamp: January 03, 2025, 02:21:43 pm
content: What kind of microscope do you have: Greenough or Common Main Objective (CMO)?Assuming you have a Greenough, I remember seeing an ad for a microscope eyepiece system that would superimpose a video source on the optical view. But where?

author: theHWcave
author_rank: Regular Contributor
timestamp: January 03, 2025, 03:58:33 pm
content: There are some very cheap multimeter (in "pen" format) on Ebay .. Bangood .. etc that apparently have actual voice readout. Disclaimer: I don't have one or ever seen on at work but from the description on these sites, such a meter could be a very affordable solution for you. They are probably not terribly accurate but for troubleshooting it would be good enough and you can use the same method to check voltages etc while looking through the microscope.Example:https://uk.banggood.com/MUSTOOL-MT007-or-MT007-Pro-or-MT007-Pro-EN-True-RMS-Digital-Multimeter-+-Voltage-Test-Pen-+Phase-Sequences-Meter-3-In-1-Color-Screen-Voice-Broadcast-p-1806010.html?cur_warehouse=CN&ID=6302089&rmmds=CategoryToolsPop&trace_id=33db1735919799211

author: inse
author_rank: Super Contributor
timestamp: January 03, 2025, 04:20:26 pm
content: That banggod thing looks clunky, probably not suitable for microprobing.Some time ago I gave away an exotic desktop multimeter from the 80‘s with speech output.There was a special probe with a button to start the voice output.

author: theHWcave
author_rank: Regular Contributor
timestamp: January 03, 2025, 06:52:42 pm
content: Quote from: inse on January 03, 2025, 04:20:26 pmI totally agree but that was not what I had in mind. Just connect your micro-probes of choice to the thing and leave it lying on the bench somewhere "in earshot". Easy!

author: inse
author_rank: Super Contributor
timestamp: January 03, 2025, 07:46:16 pm
content: I don’t know how the announcement is initiated, if you need to push a button on the _meter_, it won’t help…

author: Jane
author_rank: Frequent Contributor
timestamp: January 04, 2025, 08:15:29 am
content: I think it could be possible doing so by different sound when a cappacitor is flully shorted and when half shorted only. ( different pitch).What do you think?

author: kripton2035
author_rank: Super Contributor
timestamp: January 04, 2025, 08:29:31 am
content: build yourself a shorty-with-display. it will output sound with frequency depending on the ohm.see my signature in this message.it is designed for less than 2Ω, but I use it often to find shorts on pcbs, and it's often a capacitor cause...ps: you don't need the "-with-display" of the shorty, but it's handy to have it anyway !

author: Jane
author_rank: Frequent Contributor
timestamp: January 04, 2025, 12:31:39 pm
content: Thanks for the info.I checked your videos and also the sounds during presentatiton ( when measuring tin) but would it be possible to make a pitch difference even more different ?Yes, the shorty could be excllent for my needs.

author: kripton2035
author_rank: Super Contributor
timestamp: January 04, 2025, 12:33:21 pm
content: you have the source code available, and the line with the formula that gives output frequency vs entry ohms.you can adapt it as you want !

author: Solder_Junkie
author_rank: Frequent Contributor
timestamp: January 04, 2025, 05:31:06 pm
content: The Peak Instruments ESR meter can test capacitors in circuit. Having spent most of my working life in the mobile radio industry, including bench and field repair, I can count on the fingers of one hand the number of short circuit capacitors I have encountered. Maybe the equipment I worked on has built to a higher standard?https://www.peakelec.co.uk/acatalog/esr70-capacitor-esr-meter.htmlFWIW, the only types we found to go short circuit were tantalum ones, ignoring electrolytic ones that blew from excess supply Voltages.SJ

author: Shock
author_rank: Super Contributor
timestamp: January 04, 2025, 08:07:33 pm
content: Ceramic smd caps will also fail short circuit. In which case a short finding method is appropriate over ESR. In certain situations however an ESR meter can be used for both.The main advantage with the shorty having a display is a reproducible measurement of the short. It's easier than working out tones in my opinion.