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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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22nd Nov 2020, 12:53 pm | #1 |
Guest
Posts: n/a
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Looking for more info about this meter
Hello, I have this Milliohmeter.
I am looking for some information about it, as when was it made and what was it principal use, I found it in an old airport here in the Canary Islands. I want to sell it to buy another meter more useful for me. Help will be appreciated Last edited by Guest; 22nd Nov 2020 at 1:07 pm. |
22nd Nov 2020, 12:55 pm | #2 |
Guest
Posts: n/a
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Re: Looking for more info about this meter
The space for the batteries
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22nd Nov 2020, 1:52 pm | #3 |
Dekatron
Join Date: Nov 2003
Location: Heckmondwike, West Yorkshire, UK.
Posts: 9,637
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Re: Looking for more info about this meter
Some information here: http://bunkerofdoom.com/shal673/index.html
As usual, eBay will be a good place to look for its value, but transport and/or local values must be taken into consideration. |
22nd Nov 2020, 2:57 pm | #4 |
Nonode
Join Date: Oct 2014
Location: West Midlands, UK.
Posts: 2,181
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Re: Looking for more info about this meter
Just a shot in dark, but it might be worth looking at equipment used on rail/ petroleum installations . One of the specifications in the rail testing handbook on these places was that the resistance between rails and to earth( ground) was less than ( from memory ) 1 ohm, possibly lower.
This was in the early 80's. |
22nd Nov 2020, 3:26 pm | #5 |
Guest
Posts: n/a
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Re: Looking for more info about this meter
thanks!
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23rd Nov 2020, 1:10 am | #6 |
Rest in Peace
Join Date: Jun 2006
Location: Chard, South Somerset, UK.
Posts: 7,457
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Re: Looking for more info about this meter
For many instruments designed to measure resistance, one pair of terminals for connecting a pair of test leads is common, but here we have two pairs of terminals: probe 1 and probe 2.
With that in mind, I suspect that the method of resistance measurement used here is the Kelvin Sensing 4-wire method. The fundamental idea is to pass a known current through the low resistance to be measured using one probe and to simultaneously measure the voltage developed across that resistance using the other probe. From those two measurements, the resistance can be calculated. The principle of the Kelvin Sensing 4-wire method follows: https://www.allaboutcircuits.com/tex...e-measurement/ I built such a low resistance ohmmeter several years ago using semiconductors: it will measure resistance to less than 0.05 ohm. It is invaluable for measuring low resistances when an ammeter shunt is required, for example. Photos are attached (albeit not a very good ones: this item does not actually look that scruffy!). I do have the cct. diagram of that instrument, should anyone wish to see it. Al. Last edited by Skywave; 23rd Nov 2020 at 1:36 am. Reason: Add photos 2 & 3 |
23rd Nov 2020, 10:54 am | #7 |
Heptode
Join Date: May 2015
Location: Chatham, Kent, UK.
Posts: 947
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Re: Looking for more info about this meter
Hi yes please would like to see cct diag please Mick
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23rd Nov 2020, 3:32 pm | #8 |
Octode
Join Date: Jul 2009
Location: Cheshire, UK.
Posts: 1,706
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Re: Looking for more info about this meter
It wouldn't have been made for a specific use, it's a general purpose low-ohm meter, using the four wire Kelvin connection to compensate for lead resistance (compared with two wire measurement).
David |
23rd Nov 2020, 9:14 pm | #9 |
Guest
Posts: n/a
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Re: Looking for more info about this meter
As i said, it was in an old airport, with others specific tools for the engines of the planes
Very interesting that Kelvin method. |
23rd Nov 2020, 11:17 pm | #10 |
Rest in Peace
Join Date: Jun 2006
Location: Chard, South Somerset, UK.
Posts: 7,457
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Re: Looking for more info about this meter
mickm3for - you have a P.M.
Al. |
24th Nov 2020, 10:36 am | #11 |
Nonode
Join Date: Jan 2016
Location: Stafford, Staffs. UK.
Posts: 2,529
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Re: Looking for more info about this meter
Depending on the aircraft involved, there may have been requirements to check bonding of various parts of the plane to each other. I know of a vehicle used by the military as a radio vehicle, and all of the bolt on panels had to have the bond resistance checked.
I do have a milliohmeter, but interestingly it's my insulation tester that came from an airline's workshop. |
24th Nov 2020, 10:45 am | #12 |
Dekatron
Join Date: Nov 2011
Location: Surrey, UK.
Posts: 4,385
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Re: Looking for more info about this meter
Also, confirming effective bonding continuity of bowser hoses and fittings- without which, a bowser feeding an aircraft is like a liquid iteration of a van de Graaf generator. Just what you don't want when fuel and vapour are present in abundance.
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