Sorting those horrible slots for capacitor testing in meters

[Variometer]

For years, I have been annoyed by those slots in the front of multimeters that you are supposed to be able to push the leads of capacitors etc. I have always found it very awkward, especially with thicker leads or leads with solder on them. Dedicated capacitance and inductance meters have solved the problem in the past.

Having just obtained a new meter that measures both capacitance and inductance via these horrible slots, I decided to do something about it in order to make full use of the meter. Here is the result:
1
Bolt two pieces of 3mm acrylic together with plan of proposed plug pasted to top.
2
Cut out the two pieces at the same time. (This ensures they are both the same size).
3
Cut top half in two. Drill two holes in top of lower half and glue on two brass strips, with wires attached.
4
Glue the 2nd piece of acrylic on top and put nut & bolt through it as well. Thread wires through top holes and put two small crocodile clips on the ends.
5
The plug is now ready for use in the meter and life is a lot simpler.

Bob

[OErjan_S]

hmm, just a minor question, would not that contraption add both inductance and capacitance in a very unpredictable manner depending on frequency/frequencies and waveform/waveforms used to measure?

[Station X]

I've been using a rather cruder arrangement consisting of two 1/4" male spade terminals, designed for PCB mounting, with wires terminated in clips soldered on. It makes little difference to the reading unless low value (a few pF) caps are being measured.

The arrangement comes into its own when checking components in circuit, allowing for possible shunting of course.

[GrimJosef]

I find these sockets a pain to use too. Thanks for these tips. I'll go out and see if the spade terminals fit my meters.

Cheers,

GJ

[Variometer]

These slots aren't used for measuring frequency on my meter. That is done through the probes.

My dedicated capacitance and inductance meters both have these short test leads anyway. If when the leads are plugged in, it reads 5pf without a capacitor clipped on, just deduct 5pf or whatever from the reading with the capacitor connected. Same goes for inductance.

It only took about 15 minutes to make this morning. I think my biggest problem may be not to lose it! At the moment, I have left it plugged in the meter.

Bob

[neil29]

I know what you mean about those slots. That's why I've never bothered trying to get components into my meter . Cheers, Neil.

[Billy T]

Originally Posted by OErjan_S

hmm, just a minor question, would not that contraption add both inductance and capacitance in a very unpredictable manner depending on frequency/frequencies and waveform/waveforms used to measure?

From practical experience, no. I purchased a budget DMM with capacitance and inductance ranges for about 30 quid in your money especially for this purpose. Once I got it home I found that the lead holes were quite deep and had a stiff set of contacts at the bottom so you couldn't check anything with floppy leads. I made up an adapter (per photo) using long plated-brass pins with flying leads and mini-croc clips and they work a treat. I reverse it for inductance, but used four pins for extra stability.

With nothing connected, the base reading on capacitance is 3pF and adding in the adapter takes it to 4pF.

A vintage Lemco 22pF silver-mica reads 27pF which means its true value is 23pF. You can't ask for better than that, and anyway, capacitance and inductance values are not that super-critical until you get up to much higher frequencies than vintage radios usually use. Stability is more important than the precise cap value.

Cheers

Billy