help sought - fuse for digital multimeter

[mcbrien410]

Mike,............... 'ave you seen the price of an AVO these days? They're over 500 Quid. I just don't know how they can knock 'em out for that price. Chris

[mike ring]

[e-mail] wrote in news:1126381292.747540.223360 @o13g2000cwo.googlegroups.com:

You sure? I had to have a look and prices seem to vary from about 65 to

225?

Ther are issue variations, too.

The electric protection must have been bulletproof, but it still popped out a button to disconnect.

(We could straighten the needles by swinging it to get the needle up the other end, and at the critical moment apply reverse HT on the 50µA range.) And if the needle did fall off, well it was an Admirality cost-plus contract.

Gawd help the poor taxpayer

mike

[Owain]

I 'spect they make their profit on the AVO T-shirts and flip-flops, children's toy electrical tool-kits in a blow moulded case, and the exclusive licensed men's colognes "A Touch Of Flux" and "Burnt Selenium".

Owain

[John Rumm]

Not if you are talking the "original" model 8.

Have a look at RS stock code 653-020.... £700 quid exc VAT for the basic model. Another 50 if you want it calibrated! They want £109 extra on top of that for the case.

[Dave Plowman (News)]

They do, however, turn up on Ebay regularly often in mint condition. Go for maybe 150 quid.

[John Rumm]

Must admit I have never quite understood the big attraction with Avos. Yes OK they are class 1 accuracy, and have a nice big meter movement, but are they really *that* good to command such a price? Or is there something they will do (besides keep heavy doors proped open) that I have missed?

[Dave Plowman (News)]

They were simply the UK industry standard. Although I do have one it rarely gets used - I've got a smaller Taylor for things where a simple analogue meter might help diagnosis.

[Alan]

In message , "Dave Plowman (News)" wrote

I think the operative word is 'were'. They were outclassed on performance twenty years ago.

The price probably doesn't reflect the quality of the meter but the cost of the calibration and the tractability back to standards.

The average 'certified' electrician will be paying £100s to get their existing equipment calibrated each year.

[Dave Plowman (News)]

For many AC measurements - or anything which required a high impedance device - many more years earlier. I've got a homemade (Heathkit) valve voltmeter which is over 30 years old.

It's just the cost of making something so old fashioned.

I've got some ways of calibrating DVMs, and they don't drift that much - if well made. In some ways, calibration is a bit like CORGI etc membership. Just to satisfy the suits.

[Alan]

In message , "Dave Plowman (News)" wrote

While you may have some accurate ways of calibrating (or checking the calibration of) a multi-meter I guess the average electrician doesn't. Was that resistance measurement really 2 ohms or was it actually 4 ohms but with a partially fried ranging component?

If not subjected to (accidental) abuse the underlying DVM part of the equipment may not drift that much in a well made piece of modern equipment. Any form of accidental abuse may outwardly give an indication that no damage has been done because the meter still gives a reading but one or more of the ranges may be widely inaccurate. How many electricians are proclaiming installations are safe and are writing certificates while still using equipment that has never been checked for accuracy since they purchased it.

In some respects yes, if taken to the extreme , but also regard a regular calibration in the same way a road vehicle MOT test. Many faults are not identified until someone else checks out the equipment.

[Fred]

Not sure if that's a good analogy. A good car mechanic will have some sympathy with the car and sort important things out before an MOT. Recovery vehicles are exempt from MOTs.

[Dave Plowman (News)]

Well, yes. But assuming that damage happened just after annual calibration and certification there could be many many installations not checked correctly.

At one time the accurately calibrated speedometers in police traffic cars where checked for calibration daily...