CPC do a selection which may be suitable – see here

If you are looking for ex GPO what about the Rugby Radio Rally this Sunday at Princethorpe College?

The old BT leads were only designed for low voltage use. You should really only use leads and probes with sleeved safety plugs. Buy them from a reptutable supplier like RS Farnel, CPC or electrical factor. If you are a business or employer of any sort you must use appropriate safety leads. For domestic mains on the "user" side of the socket they should be "CAT II" at least andfor house wiring work CAT III see http://www.hse.gov.uk/pUbns/priced/gs38.pdf

Robert G8RPI.

Testing has become increasingly difficult as the requirements for shrouding have become more onerous. Needle points are useful for checks on PCBs that have been lacquered, they can also be useful for piercing the insulation on cable, obviously this must only be used where the pinhole left will not compromise the safety and integrity of the installation and personnel. Sometimes you can have fond memories of slate backplanes and rigid bare interconnections, accessibility was easy but so was an accidental touch when live testing.

Mike

The 4mm plugs with spring loaded sleeves are pretty useless and no longer common (or acceptable for new mains rated leads).

When teaching use of meters I had a "lesson" on digital accuracy. It involved a PP3 battery, AVO Model 8 analog meter (1%) and AVO DA116 digital meter (0.5% +1 count). Tne lesson was to measure the battery with both meters and discuss the results. The Model 8 read around 8.4V and the DA116 read 9.0V. Most students said the Model 8 was out of calibration and inaccurate (dispite having a in cal sticker) by 0.6V. A small percentage said the DA116 was faulty. – these had noticed that the PP3 was a rechargable with a nominal voltage of 8.4V. The DA116 had been deliberately adjusted to over-read. More digits does not mean more accuracy. The DA116 was only good to +_ 0.055V making the last digit virtually useless.

Robert G8RPI.

No, very much more accurate, at least if the agreement of multiple meters on a reading and the occasional test against an accurate reference voltage is sufficient test. Essentially, it isn't any more expensive to make them accurate to within a few tenths of a percent, so there's no incentive to make them less accurate.

Neil

E-Z Hooks were one of my favourite small probes for bench repair work E-Z Hooks

Mike

Hi Neil,

I doubt any cheap meter is an order of magnitude more accurate than an expensive anlogue meter. A classical analogue meter like an AVO 8 has a specificed accuracy of 1% on DC volts. Even a good 31/2 digit DMM e.g. Fluke 110 series is only specified to 0.7 percent. plus 2 counts. Any 31/2 digit meter (1999 count) has only 0.05% resolution so with the best uncertanty of 1 count even if everything else is perfect they can only make 0.1% of full scale. Accuracy for AC, current and resistance is poorer. A single point check is not confirmation of overall accuracy.
Accuracy, precision, resolution and linearity all need to be considered. A great book on the subject is "Calibration Philosophy in practice" by Fluke.
I'm a bit of a ""volt-nut" I have meters up to 81/2 digit resolution, good solid state voltage references, Kelvin-Varley dividers etc.

Robert G8RPI.

Edited By Robert Atkinson 2 on 16/08/2019 11:11:09