Where to buy rotary switch and digital panel meter?

[Dave]

I've spent the last 30 mins going through RS, Maplin and Farnell sites without success - HELP! I need a 2pole 4way rotary switch that's rated at 600V (negligible current, break_before_make) and a cheap AC digital panel meter (3 or 4 digit) that I can use for a voltmeter to measure up to 600V (with suitable external divider). Can anyone point me at a supplier?

Dave

[Gordon Hudson]

These switches might do as they are ceramic:

[Frank Erskine]

On Sun, 23 Jul 2006 21:26:57 +0100, Dave had this to say:

Try:

may be wholesale only, but might be able to let you know of any retailers (or even send you a sample foc !)

[Dave]

Thanks, for some reason I hadn't thought of eBay for this sort of thing! They're actually a bit too pricey for what they are but looking at the pics has given me the idea of just getting a standard 2 wafer rotary and removing alternate contacts to improve the voltage rating - unless I can find something that's actually rated for what I need.

Dave

[Bob Minchin]

IF you've been to Farnell you will have seen their 1999vac fullscale meter.

1volt resolution. Is this no good?? part no 3099830

As for the switch, the voltage will likely restrict you to industrial control switches which are not cheap and made up with switch modules fitted onto a detent mechanism. I agree - not easy to find.

A low voltage switch plus relays might be workout cheaper?

Good Luck

Bob

[Frank Erskine]

On Sun, 23 Jul 2006 21:13:18 GMT, "Bob Minchin" had this to say:

I don't know if it's still possible to get "Yaxley" switches, which were very popular in the 60s. There were similar ceramic things, which were great for high voltages.

Hang on a mo...

Dives into shack - bottom drawer of desk I think...

Eureka - I have a 2-pole 4 way ceramic switch which just wants a bit of a clean-up with Servisol. It's yours for the cost of postage...

[Dave]

Thanks Frank!! I've sent you an email.

Dave

[Dave]

... snipped

Thanks Bob, TBH I'd missed it but maybe it was the price that put me off. When a cheapy DMM can be had for £10-20 it seems a bit much to pay £50 for a DPM - maybe I'm just being too tight ;-) Quack!

Dave

[Tony Williams]

A hidden advantage of using a low voltage DMM is that it needs an attenuator. This means that a high voltage attenuation resistor can be placed in series with every incoming hv line. These resistors usefully limit any transient or fault currents through the switch.

[Dave Plowman (News)]

Have a look at Lascar. They'll be easier to mount than trying to adapt a cheap DVM.

[Dave]

Thanks, but the (few) AC ones are relatively expensive. Why does an AC function make these DPMs so much more expensive than the DC ones? - ISTR that back in my designing days the standard way to do RMS conversion was to use a couple of ap-amps with diode feedback - surely that's a virtually "free" function these days.

Dave

[Andy Dingley]

Don't use wafer switches over 50V, unless they're designed for it (ceramic wafers and physical gaps). You get carbon tracking across the paxolin, no matter what distance.

Old valve radio wafer switches, or S/H industrial cam switches are the things to use though. Not cheap new, but they're around S/H. Greenweld used to have loads.

[Dave]

I ordered a Moeller "voltmeter switch" (obvious when you think about it!) that's made for the job at £11.98 -25% +17.5% ... not too bad.

Dave

[Dave Plowman (News)]

My old, but top of the range Maplin DVM with rotary switch went bang when measuring - or trying to - mains voltage. It was brass dust from the tracks bridging the insulation between them.

[The Natural Philosopher]

A not uncommon failing.

Switches for HV are made on different principles often.