Another YouTube channel worth a look

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Hi

I'm addicted to the videos of this chap called Andy Davies, whose channel is called AndyDaviesByTheSea. He does a lot of stuff about old radio equipment and test equipment, but even if that doesn't sound like your cup of tea give it a go anyway - it's fascinating. There's a recent video about him fixing a Telequipment scope (which is how I found him). He says "It smelled like a selenium rectifier packing up, if you know what that smells like". Priceless. He also makes forays into horology, which appeals to me no end. I admire his ability to make things out of the contents of a junk box without thousands of pounds worth of tools. I don't think he has a piece of test equipment made in the last 20 years. Makes me feel like a charlatan.

Anyway, check him out.

Cheers
John

Moderator: Added link

[PeterG]

I found him a while ago, he makes very interesting videos.

Regards

[ablacon64]

Didn't know about it, just subscribed! Thanks for the tip!

[KF5OBS]

An old-timer, must me great. Just subscribed. Thanks for sharing that with us.

[G7PSK]

Just looked at the link, and watched No.53. I would like to see Dave measure 2KV with a fluke, just shows how good the old AVO's were

[SeanB]

I checked the output of my insulation tester with a cheap DVM, that I can get cheap if it did not survive. 1053V on the 1000V range. Meter input impedance was measured as well, 10M on the insulation tester ( actually 5M indicated, but there is a scale factor to the 1000 and 250V ranges) which agrees well with the quoted spec for the meter and the tester.

[M0BSW]

Hi

I'm addicted to the videos of this chap called Andy Davies, whose channel is called AndyDaviesByTheSea. He does a lot of stuff about old radio equipment and test equipment, but even if that doesn't sound like your cup of tea give it a go anyway - it's fascinating. There's a recent video about him fixing a Telequipment scope (which is how I found him). He says "It smelled like a selenium rectifier packing up, if you know what that smells like". Priceless. He also makes forays into horology, which appeals to me no end. I admire his ability to make things out of the contents of a junk box without thousands of pounds worth of tools. I don't think he has a piece of test equipment made in the last 20 years. Makes me feel like a charlatan.

Anyway, check him out.

Cheers
John

Moderator: Added link

.
Thank you for the link,  As a  fully licensed radio amateur myself, i can relate to Andy , and his videos are brilliant, I got a few to watch

[M0BSW]

Just looked at the link, and watched No.53. I would like to see Dave measure 2KV with a fluke, just shows how good the old AVO's were

I was offered one of those and turned it down how dumb was I Arghhhhhhhhhhhhhh

[G7PSK]

Just looked at the link, and watched No.53. I would like to see Dave measure 2KV with a fluke, just shows how good the old AVO's were

I was offered one of those and turned it down how dumb was I Arghhhhhhhhhhhhhh

The scope or the AVO. I used to have a similar scope and still have the AVO which is still a good meter. I have a couple of DMM but if I think there might be large transients or I want to measure HT I roll the AVO out best meter ever produced bar none to my mind. A proper mans tool.(For many things but no good for teeny weeny weedy electronics)

ps. my tongue was so far in my cheek for that last bit I may never be able to make adjustments again.

[M0BSW]

Just looked at the link, and watched No.53. I would like to see Dave measure 2KV with a fluke, just shows how good the old AVO's were

I was offered one of those and turned it down how dumb was I Arghhhhhhhhhhhhhh

The scope or the AVO. I used to have a similar scope and still have the AVO which is still a good meter. I have a couple of DMM but if I think there might be large transients or I want to measure HT I roll the AVO out best meter ever produced bar none to my mind. A proper mans tool.(For many things but no good for teeny weeny weedy electronics)

ps. my tongue was so far in my cheek for that last bit I may never be able to make adjustments again.

I'm looking on E-Bay at one now , I intend to correct the mistake I made, as my Transceivers are all high voltage Yaesu FT101 ZD, Kenwood 820, 820s, 520s, big voltage boys.

[IanB]

A handy trick for anyone who might occasionally want to measure a voltage like 1.8 kV which exceeds the DC V range on a multimeter. If you have two meters, put them both on the 1000 V DC range and connect them in series when taking the measurement. You will now have a 2000 V range. Add together the readings on each meter to get the total voltage.

[alm]

Assuming the input impedance is the same. What happens in the case of an overload? CAT III 1000 V standard overload test is an 8 kV transient, so lets assume 16 kV for 2000 V (no idea if there's actually such a thing as CAT III 2000 V, let alone what the test conditions are). The MOV in one of the meters will start clamping the transient. This essentially shorts the inputs of that DMM, and puts almost the full transient across the second DMM, which might catastrophically fails since it suddenly gets to dissipate twice the voltage transient it was designed for.

This assumes the meters were properly designed, like the Fluke 27 that Dave recently reviewed. I wouldn't even trust some random cheap DMM which skimped on safety features, eg. Uni-T, to handle its rated transient, let alone twice that.

[IanB]

I was going to add a comment at the end of my post that such techniques should only be used for low energy electronic circuits on the bench, but then I removed it because I thought such a thing would be obvious. It is clear to me that if you have to measure 2 kV DC in an industrial setting where high energy transients might occur then you will of course have appropriate (safe) instrumentation and training available to you.

It is of course best to use two similar or identical meters so that the voltage is divided roughly equally between them, otherwise one meter might go over range.

[SeanB]

The meters in series works for analogue meters where the input is totally resistive well into overload, but is not good on a digital meter where the input impedance can be modified by overvoltage protection or by other protective methods like a PTC fuse.

Of course the analogue meters must be the same make, model and mod state, otherwise all bets are off.

[alm]

Or you could use a proper resistive high-voltage probe, which is much more likely to be purely resistive well beyond the max. voltage. Shouldn't cost much more than another multimeter. Of course these are usually only designed for low energy circuits.

[IanB]

The meters in series works for analogue meters where the input is totally resistive well into overload, but is not good on a digital meter where the input impedance can be modified by overvoltage protection or by other protective methods like a PTC fuse.

I'm really failing to understand the concern here. If you overload a single DMM on the DC V range, you may damage the meter. If you now put two meters in series each on the DC V range, you run the risk of damaging two meters. OK, that's slightly more painful than damaging one meter, but presuming you use two similar meters and keep the total voltage in range the risk is minimal.

A second use for this trick is to get more digits of precision when measuring lower voltages. For instance if you have two 4000 count meters and you want to measure 5 V, you could have 5.00 V on a single meter, or 2.498 V + 2.502 V on two meters in series.

[alm]

The bang might be larger (four times as large in the worst case of one meter completely shorting and the other behaving as a resistive load seeing twice the voltage). Granted, the risk should be quite small as long as you have decent meters and stay within their limits.

You get more digits of precision with two meters in series, but accuracy may be worse if the offset error (+ n digits) dominates, since you double this offset error.

[EEVblog]

Just looked at the link, and watched No.53. I would like to see Dave measure 2KV with a fluke, just shows how good the old AVO's were

Why would I, I've got a Tripplett that can measure 6KV.
I wonder if the old AVO's survive an 8KV 2ohm transient?

Dave.