29-07-2016, 11:33 AM
That's a Mk. 5, often regarded as cheap tat from Thorn
The Movement should clean up OK.
Alan
The Movement should clean up OK.
Alan
DMM
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29-07-2016, 11:33 AM
That's a Mk. 5, often regarded as cheap tat from Thorn
The Movement should clean up OK. Alan
29-07-2016, 01:18 PM
I've got a bunch of Fluke DVM's (And AVO 8's etc) and absolutely agree that the Flukes hold their calibration for an eternity. As do well cared for AVO 8's.
However, I needed two cheapish DVMs to measure heater voltage and current as part of a valve curve tracer project. I needed 0.1V to 100V ACV and 100mA to 10A ACI. I bought two of these http://www.ebay.co.uk/itm/VC97-Accurate-DIGITAL-LCD-VOLTMETER-MULTIMETER-WIDE-RANGE-TESTER-AMMETER-AC-DC-/321133117131 . Took the cases off, removed transistor test socket, thermocouple socket and input sockets. Hard wired the range switch to V and I with a transistor reset soldered in where the AC button was. Cut two rectangular holes in the chassis for the displays to poke through and I have autoranging ACV and ACI panel meters for a total of >£34. Accuracy is comparable to my Flukes - and amply accurate enough for the use. Of course it had a fake CE mark, and allegedly is Cat II. This is of course absolute Chinese nonsense and for £17 each I expected precisely that, but it is much less of an issue when the guts are mounted inside an aluminium instrument case. My advice for a pukka DVM, I'd wait around for a good Fluke to appear on eBay. 8060A's are a goodie if you can get one (lots in the US). Do not under any circumstances buy an alleged Fluke meter from either China or Hong Kong - they will be ripoffs with 100% certainty. From my £17 meters here is a large amount of plastic, probes (rubbish quality), cardboard etc went straight in the recycling.
29-07-2016, 02:58 PM
I do like you approach. By the way, I think you meant '<£34'.
How did you Power them? Alan
29-07-2016, 05:27 PM
I toyed with the idea of external power. But since the power draw is tiny, it will only get occasional use, and the supplied batteries are 2 x AAA size, I have just used a panel mount (Bulgin) 2xAA battery holder with an on/off switch. That runs both meters. Battery life will probably be dominated by shelf life rather than depletion.
And you're right - I got my greater than and less than wrong! Craig
30-07-2016, 07:57 PM
(28-07-2016, 10:37 PM)Mark Hennessy Wrote: I've got a handful of Flukes (slight understatement!). You can see some here: http://www.markhennessy.co.uk/dvm_reference/#postscript - note the range in ages and price, yet note how they are all bang-on. None of them have been adjusted in the time I've had them (most were second-hand). Flukes hold their calibration for decades, and are very well made and rugged (both mechanically and electrically). I've got a Wavetek RMS225 which bears quite a resemblance to your Ex MOD Fluke. I've had it for years and it still performs well, though I've no way of checking its calibration. I believe it was originally marketed under the Beckman trademark.
02-08-2016, 12:41 AM
(29-07-2016, 11:29 AM)ppppenguin Wrote: I've dug it out. Unfortuantely the movement is slightly sticky. Don't know how fixable it is. If you want it you're welcome to it for the cost of postage plus a very small donation. Thanks Jeffery The fleabay meter I bid on fell through (outbid) I'll go with your mk5 if it's still available if I may Dick.
I was there when Rock & Roll was born & Rock & Roll will be with me till the day I die.
02-08-2016, 06:17 AM
I reckon it will go RM Small Parcel for £2.85. I'll PM you with my Paypal details and in return I'll need your address. If you include a small Museum donation with the postage it will get to the right place.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
Although I'm using two cheapo Chinese meters inside a metal enclosure to measure heater current and voltage, there is no way I would use these for any serious measurement, particularly on a high energy circuit. The probes which came with them say "Cat III" which they most certainly aren't - they are CAT I with a following wind. The probe tips are far too long, and they have a double insulated symbol, but use single insulated wire.
Although this is a Fluke video, it is a good round up of what voltage categories are, what you have to look for, and even (if working at or near a mains incomer) what clothing to wear and the chilling consequences of not doing so after an arc flash. Plus some scary tests on cheapo meters, like connecting to volts on the ohms range, or volts when the plugs are in current sockets - flames and explosions. https://www.youtube.com/watch?v=IzwN8yibjjA All my DVM's (5) and probes are Fluke, and in fact have just bought a set of high energy CAT III/CAT IV probes from Farnell (£59 plus VAT) in the event that I have to work on our domestic distribution board - which I have done in the past. Best have them on hand. |
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