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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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2nd Apr 2020, 12:20 pm | #1 |
Octode
Join Date: Apr 2019
Location: Margate, Kent, UK.
Posts: 1,728
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Plug in Shunt for Avo mark 4 multiminor
Does anyone know what a plug in shunt for the Avo mark 4 multiminor looks like or if you can make one up. I want to measure AC mV but not able too as mA is DC only on the meter and it seems according to booklet you need a plug shunt then insert test leads into that.
Cheers |
2nd Apr 2020, 5:14 pm | #2 |
Dekatron
Join Date: Aug 2016
Location: Colchester, Essex, UK.
Posts: 4,106
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Re: Plug in Shunt for Avo mark 4 multiminor
The copy of the booklet i am looking at says only 4 external accessories were available:
One for high DC voltage, and three for DC current. If you were able to measure AC mV with this meter by some means, i doubt the accuracy would be much good. Dave |
2nd Apr 2020, 6:07 pm | #3 |
Octode
Join Date: Oct 2007
Location: Exeter, Devon, UK.
Posts: 1,554
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Re: Plug in Shunt for Avo mark 4 multiminor
Shunt for AC current on Avo Multiminor.
The varying resistance of the rectifier means that a simple shunt cannot be used for AC current measurement. See Scroggie. Radio Laboratory Handbook - try 6th Edition, p93 or earlier editions. You will have to make a transformer, rather as the Avo 7 / 8 do. Your shunts will be for DC only. I suspect that you could use a shunt with a moving iron meter, as that responds equally well to AC as DC. But as the impedance of the coil will vary with frequency, the calibration will only be valid at one single low frequency. Has anyone experimented with this. I will see if I have a moving iron meter somewhere. wme_bill |
2nd Apr 2020, 7:07 pm | #4 |
Octode
Join Date: Apr 2019
Location: Margate, Kent, UK.
Posts: 1,728
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Re: Plug in Shunt for Avo mark 4 multiminor
Cheers guys the booklet I have is pretty limited in info just how to read the meter and a small section on using a shunt connected to the + -ve terminals then connect the test leads to the shunt for DC mV readings. Read it wrong DC only shunts 5,10, and 25A not AC.
Does not do a great deal really pretty basic but I'll use it see how readings compare with my DVM. I have a GPO one not even looked at that yet maybe that will have a bit more usefulness. Cheers |
2nd Apr 2020, 9:12 pm | #5 |
Heptode
Join Date: Mar 2008
Location: Forest of Dean, Gloucestershire, UK.
Posts: 648
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Re: Plug in Shunt for Avo mark 4 multiminor
The 10A shunt looks like this and, though I've never seen them, I imagine that the other are similar.
Hugh |
3rd Apr 2020, 10:26 am | #6 |
Octode
Join Date: Apr 2019
Location: Margate, Kent, UK.
Posts: 1,728
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Re: Plug in Shunt for Avo mark 4 multiminor
Ah I thought they had to plug in. Must admit I've never seen them sold with AVO meters or singly. Must be quite rare or there was not a major demand for them. I suppose measuring up to 5, 10 to 25A was not often needed not sure what equipment would give you a 25A reading TV maybe?
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