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Old 24th Oct 2021, 12:52 am   #1
paul1962
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Default AVO meter help required.

Hello everyone
Firstly, many thanks to those who are interested in my thread and taking the time to view it.
OK, here is the scenario ..
I have an AVOMeter Test Set No 1 (ex NATO equipment). I have replaced both batteries with new units, the voltages are seeming to work fine on ac, and I believe this to be the case on dc also (although, to be fair, the reading on a brand new D cell appears to be 1.3 rather than 1.5V, but possibly a slightly old stock battery)
The ohms settings can be zeroed on the high range and also the low range on the meter, BUT .. on the mid range ( ohms divided by 100 setting), I cant get this to go any lower than 100 on the meter, even with the adjustor at full tilt. It was originally sitting at 500, but I removed the main workings and cleaned up the contacts as best as I could, which has resulted in the last 100 readings now.
So, I guess my question is why is this ahppening and how do I correct it ? Is this a known issue with these AVO's ? I know they are high sensitivity models, but being ex NATO spec (with potted components etc) I would assume that these would be catered stronger for harsher environments etc.
Over to you in the know and all input greatfully received.
Many Thanks in advance.
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Old 24th Oct 2021, 1:47 am   #2
Refugee
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Default Re: Avo meter help required

The divide by 100 range only works with a brand new D cell.
1.3 volts will not be enough and you will never get it to zero.
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Old 24th Oct 2021, 7:34 am   #3
Phil G4SPZ
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Default Re: Avo meter help required

Yes, pristine-clean contacts and a fresh D cell are absolutely essential.
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Old 24th Oct 2021, 1:16 pm   #4
paul1962
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Default Re: AVO meter help required.

Thanks for your input so far guys
I guess it's off to get some more batteries that are better than these damn Duracells
Any recommendation as to a good reliable battery these days ? (I have no doubt that they are all made in China and rebranded), but maybe there is something decent that won't throw its content all over the battery compartment
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Old 24th Oct 2021, 1:18 pm   #5
Phil G4SPZ
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Default Re: AVO meter help required.

I order all my batteries online from CPC Farnell. They don’t leak, in my experience, but any cell left for years in a discharged state is likely to cause trouble.
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Old 24th Oct 2021, 1:23 pm   #6
paul1962
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Default Re: AVO meter help required.

Hello Phil,
I have just checked for a D Cell on their site and the only one they seem to list is rated at 1.2V and 4AH.
This puts them at about the same range as the Duracells I have
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Old 24th Oct 2021, 2:07 pm   #7
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Default Re: AVO meter help required.

My AVOs work fine with Aldi batteries and 5 CR2032 cells and a spacer for the high range.
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Old 24th Oct 2021, 2:08 pm   #8
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Default Re: AVO meter help required.

Hi Paul,

If it is 1.2 V and 4 Ah it is clearly a rechargable D type you are looking at.

These are not suitable for Avo meters.
You really need 1.5 Volts or very close too it.

Get yourself down to B&Q or Screwfix and buy some Varta D Types.
As far as I know, they are still made in Germany.

The Battery you measured at 1.3v, if it was a regular Battery and not a
rechargable, it is as good as completely Dead.
Assuming of course you measured it with a known good Voltmeter, and not
a currently suspect Avo meter.

A fresh primary D Battery should read around 1.6 Volts.


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Old 24th Oct 2021, 5:32 pm   #9
The Philpott
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Default Re: AVO meter help required.

New alkaline D cell (or even a zinc chloride will do)
Anything but a duracell.
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Old 24th Oct 2021, 8:28 pm   #10
mark_in_manc
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Default Re: AVO meter help required.

(I opened an AVO8 mk5 this afternoon, and found a nice blue Ever Ready SP2! No trace of a leak...or any current )
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