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Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders. |
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19th May 2023, 7:39 pm | #81 |
Dekatron
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Re: Old or New multimeter?
No... But you can keep screws, washers and other take-to-bits items in the meter glass recess!
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Regds, Russell W. B. G4YLI. |
19th May 2023, 9:51 pm | #82 |
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Re: Old or New multimeter?
Quite-we've all done it and it does no harm- but ensuring the pointer reading is honest should be done by rocking the meter on it's tripod feet, not tapping the glass!
Dave |
15th Jun 2023, 11:05 pm | #83 | |
Pentode
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Location: Clovis, California, USA.
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Re: Old or New multimeter?
I use a Simpson 260-6 since 1978 works great
It still made today itis a life time investment by one for life. Dave Quote:
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16th Jun 2023, 5:57 pm | #84 | |
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Re: Old or New multimeter?
Quote:
I'd love an Avo 8, just 'cos it's an Avo 8 and everyone involved in electronics should have one I have 2 or 3 that have been donated over the years but all have a fault which renders them BER. Namely a sticking meter movement on 2 of them. IIRC the third has lots of charcoaled bits where it must have been connected to a high voltage low impedance source such as 415V mains on a very wrong range... |
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16th Jun 2023, 6:23 pm | #85 |
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Re: Old or New multimeter?
I had a rare case of the input resistance of a DMM being the source of measurement error just a couple of months ago. I'd designed and built myself a high voltage bench supply for use with valved equipment and a "USP" is quite high precision (not really necessary of course to be able to precisely set a valve HT supply to within 1V or better and have it stay put to within a couple of mV over hours but the way the design was going naturally lent itself to it and I hadn't the capacity to resist).
Voltage dividers for the three ranges were calculated and suitable resistors dug out but to get ultimate accuracy I allowed for a SOT resistor to make up for tolerances etc. A temporary preset was employed to find the best SOT resistor and as a final/sanity check the divider output was measured and referenced against the measured output voltage. Well there was a discrepancy wasn't there... just maybe a couple of percent ish but seemingly unexplainable and it had me virtually pulling my hair out! Then a eureka moment as it dawned on me that the 10M input resistance of the multimeter was having enough effect on the measured voltages from the dividers (which are made with resistors in the 100's of K region) to cause the discrepancy. I'd got just so used to ignoring the Input Z of a DMM as it's so high as to be negligible... except when it isn't! I went back to my spice simulation and made allowances for the 10M of the meter so I knew what I should be reading on the meter when allowing for this and all's well |
16th Jun 2023, 10:46 pm | #86 |
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Re: Old or New multimeter?
Jez, might the AVO 8's suffering a sticking pointer merely have ferrous fragment/s obstructing the movement..? - a problem that a steady hand, a head torch and a set of jeweller's loupes can rectify?
Dave |
16th Jun 2023, 11:48 pm | #87 | |
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Re: Old or New multimeter?
Quote:
The internet is so full of both apocrypha as well as good info but I vaguely recall reading that in cases of a sticking pointer on an Avo 8 you would be incredibly lucky or skilled to ever get it back working as it should (some esoteric but believable reasons were given IIRC) and that it was a fools errand to even try... which sounds vaguely ridiculous reading that back but the guy seemed a real expert on Avo 8's .... IIRC! |
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17th Jun 2023, 12:03 am | #88 |
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Re: Old or New multimeter?
..I reckon on 2 out of 3 sticking pointers being fixable, either by aforementioned debris removal or backing off one of the jewels slightly.
The remaining 1 out of 3 usually seem to be down to a damaged jewel, and require watchmaker skills and a donor meter... most of us (including me) wouldn't even try. I assume this is the scenario said expert was referring to. I agree there is a lot of flannel on the 'net. 'Cool your home down in 90 seconds with this brilliant new hack' etc etc. Dave |
17th Jun 2023, 1:11 am | #89 |
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Re: Old or New multimeter?
"Blah blah resetting jewels blah blah only a few in the UK can properly do it" seems somewhat what I remember yes! Like I say it was years ago when I had a quick look at them and then googled it.. we're talking 2000 or XP I'd have googled it with!
All the talk of analogue meters then mention of a TMK meter and my remembering that was the brand I bought as a lad and wondered if it still worked (I dug it out and tried it. it does. And Ohms could be still be zeroed on the higher ranges with the battery that's prob been in for at least 15 years.no not the original!) and it got me thinking about the Avo 8 and how everyone in electronics should have one by law etc and that I actually had a few I'd not looked at for years... So many projects going on (whether for me or customers) and so few round tuits |
17th Jun 2023, 2:42 am | #90 | |
Pentode
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Location: Clovis, California, USA.
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Re: Old or New multimeter?
Most time you do not here on DMM or other
electronic volt meters about is the refresh rate. This because they a slow computer for calculations for voltage and ohms. . Worst on low end DMM than high end high cost. About the only time use a digital meter is checking resistors. Everything else is the good old Simpson 260. Dave Quote:
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17th Jun 2023, 10:18 am | #91 |
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Re: Old or New multimeter?
That is indeed a relevant point: Sampling Rate and Refresh Rate. Certain Auto ranging DMMs also take a long time to make an initial decision- my Uni-T meter is like this on Ohms and Volts. I don't actually mind, but i can see how it would grate on people doing repetitious tests in a hurry.
Dave |