help oldish multimeter

[robert the violinist]

How are the RS pro  DMM`s in around the £ 50-100 price range??  Particularly the RS PRO IDM66RT as its on offer at the moment. Or are their any brands almost as good as Fluke only cheaper?
Thanks
Also is this on ebay the same as the RS pro idm66rt with  different branding? Both made in Taiwan.
https://www.ebay.co.uk/itm/ISO-TECH-IDM6...3478602494

[Mark Hennessy]

It looks like it uses the same DTM0660 chipset that many of the cheap meters use. Personally, I doubt it's worth paying extra - the Aneng meters are very good for the money. I certainly don't think the RS Pro 14 is worth the extra over the cheap equivalents I reviewed, but at £20, it's less of an issue. The RS Pro 14 is made by CEM - no idea who makes the IDM66. Whoever makes it, it won't have Fluke's build quality.

My current cheap favourite is the Bside ZT301 - review here: https://www.eevblog.com/forum/beginners/...msg1344853

I haven't explored the market for a couple of years now, so there might be better options, but this one is a really nice balance of features for the money.

If you wanted something that is better built, I would jump up to the Brymen BM235. It's about £100, and is genuinely CAT IV rated. You can pay a bit extra to get the EEVBlog version, which has a different colour holster and much better leads. There are some Flukes available at that price point if you don't mind risking a grey import via eBay or similar.

The £20-£100 market is a bit "meh" IMHO. Either go cheap-but-good, or do it properly.

[robert the violinist]

Thanks Mark,  as mentioned earlier i bought a Extech ex430 off ebay  , after i bought it i started reading horror stories all off about the dodgy selector switch. It arrived today and ive just tested a resistor and a 9v battery to try it out. Havent noticed anything wrong with the selector knob as yet but its far more complex than im used to and i may yet come across that problem.
One breakdown of one  i read ,showed poor soldering and questionable protection .  I will be using it for guitar electronics but also adjusting bias on valve amps  up to 450v ,so not sure if its suitable as yet. Mainly sticking bias probes that go inbetween the valve socket on the amp and the valve to read plate voltage and current.
Bob

[Terry]

Hi Bob, I note your comments about the Extech ex430, which I note is now obsolete, but you seem to have got it at a reasonable price, so long as the shipping costs were low, so I hope you don't have any problems with it.

However, it shouldn't break the bank if you do have to replace it.

[ppppenguin]

450V with a fair current behind it is dangerous, though it's not like mains, with very high current available that could cause arc flash. So look at the probes carefully and possibly buy a higher quality set. Also attach the probes before switching on where possible. It's all too easy for a probe to slip with unpleasant results. Many years ago I got bitten by 1200V DC, mains derived, from a 'scope I was probing. It ******** hurt. The problem was a probe whose insulation wasn't as good as I thought it was.

I'm sure I don't need to tell you all this but a safety reminder doesn't hurt. Unlike a 450V HT belt.

[robert the violinist]

Jeffrey, the probe ill be using  is this which looks well built  and plugs directly into the dmm (the extech ex 430 above) to take  plate voltage and current readings.  I may have to use the normal probes that came with the multimeter to  measure the cathode resitor value and voltage drop but other than that i dont envisage poking around anywhere else. I would of course discharge the capacitor first  before doing the latter.
Heres the instructions given with the bias probe if anyone cares to comment.
Im a bit worried about the cat rating on the extech though after watching a couple of teardown/reviews and the fact the bias probe has the unshrouded banana plugs .
Bob
https://www.eevblog.com/forum/testgear/e...-teardown/

[ppppenguin]

The Cat II rating should be fine for your purposes. I wouldn't like to use it for mains where there's a lot more energy available. The amplifier HT may be able to give a few amps in the event of a short circuit but it's not the 10s or 100s of amps you can easily get from the mains. The hazards in lower quality DMMs are usually about what the PC tracks and fuses will do in the event of a high current surge. With arc flash as the really nasty consequence when you have 100s or 1000s of amps available. You won't get arc flash downsteam of an ordinary ring circuit 32A fuse/MCB.

While you're obviously going to keep your hands clear of the 4mm plugs (unshrouded with a cross hole) I'd do an insulation test on that switch toggle which you will be touching. 500V DC minimum, 1000V is better.

[Old Sparky]

That Skytronics DMM appears to be identical to my M4800, except that the highest DC current range on the 3800 is 20A rather than 10, not that I'd use the leads/probes supplied for high DC ranges. I find the 3800 very useful, but miss the auto-ranging feature of my Fluke 75. The 3800 I have, bought at the NVCF a few years ago, doesn't have a CE mark or the 'Cat II' mark between the 'COM' and 'V Ohm' sockets. It may be a Chinese copy of the original M3800, but there is no indication on the meter, the box in which it came, or the instruction booklet, as to it's country of origin. Regarding test leads & probes, as well as being 'fit for purpose, one of my pet hates is that few have probes that can be rewired without cutting the probe open to gain access to the probe tip end. Perhaps the best lead sets available are the genuine Fluke ones.

[Terry]

I note in that picture that the meter, although not in use, is set to its most sensitive range: 200mV DC.

It is a golden rule that, if there is not an off position on the selector (which the Extech does have) is that the meter should always be left set to the highest possible voltage range - in this case 1000VDC - to provide the greatest degree of protection to the meter.

As an example, imagine what would happen to that meter if you connected it to a 450V HT rail and omitted to set the correct range first! After all, accidents can and do happen!

That tear down comments on the poor quality of the soldering. This is not uncommon. Many items like this are made by numerous manufacturers and build quality varies enormously. From memory, I think Bangood are usually well respected for the quality of the items they sell. Without taking it apart you won't know how good (or bad!) the quality of your new acquisition is.

[robert the violinist]

Terry i wont be using that meter, its the extech im using. that photo was just to show that the unshrouded banana plugs wouldnt fit that particularly meter.

Also im unclear about no10. on the instructions for this bias probe " its says set the meter to the mv range (200mv) to get reading in Ma. SHould that be set the meter to the ma range to measure the plate current in ma.???

I`m assuming i would have to swtich the amp off and then set it up as the current uses a seperate input jack on the meter and i dont want to be unplugging the probe jack with power on???