Old Megger Test Meters Help ! - UK Vintage Radio Repair and Restoration Discussion Forum

johntech · 31st Mar 2018, 1:15 pm

Hello Folks
I have recently been given a megger insulation tester (hand cranked type) and a low ohms meter the insulation tester is red and the low ohms meter green.
The insulation tester works fine but I cannot fathom how to use the ohm meter.
It has three terminals and a floating meter movement the battery is a pocket flash lamp type 4.5 volt.
Has anyone got the instructions for this meter.
I reckon could be 50-70 years old like me !
Any help gratefully received.
Thanks John

Refugee · 31st Mar 2018, 2:27 pm

Have you checked the battery with a bulb?
It may read all right with a meter but the loading from a low ohms range will need a fresh battery.

johntech · 31st Mar 2018, 9:56 pm

Thank you for your reply the battery is fine. The mystery is that the meter has 3 connections and somehow the meter must nullify the resistance of the test leads as there is no zero adjust pot.
I'm sure there is an easy answer but what !

Refugee · 31st Mar 2018, 10:14 pm

That sounds like one with a single sense wire.
It senses the resistance of one wire and assumes the other wire is the same resistance so the main leads need to be in good condition.
Have you got any photos?

Ed_Dinning · 1st Apr 2018, 7:55 pm

Hi John, I have one of these somewhere, it has a twin probes, one of which has 2 wires, the other only 1.
It looks to be as described above in that it compensates for lead resistance.
It apparently came in 2 versions.
The 2 wire unit had a battery button on the meter
The 3 wire unit had a battery button on the 2 wire probe.

Ed

johntech · 1st Apr 2018, 9:35 pm

Hello Ed & Co
Thank you for your replies.
There is no battery switch on the meter and there are no test leads either !
So I assume all three test leads should be identical wire.
Presumably two leads are connected together which gives the meter its zero reading and the third lead plus the two others can then be used to take a measurement ?
Do you think I am on the right track or talking rubbish as usual !
Its strange because these continuity "Meggers" were very common I can remember the electricians where I worked as a TV engineer having them and yet there is nothing that I can find on the net relative to them !
Perhaps someone somewhere has the original instructions we shall see.
Best Wishes John

Ed_Dinning · 2nd Apr 2018, 8:07 pm

Hi John, I may have the instructions "somewhere" but I believe the 2 leads from the adjacent terminals are taken through a switch to turn the meter on. A probe goes from one of these wires.
The other meter terminal goes to the other probe.

If you are going to Golbourne on Sun I'll try and bring the meter along to show you.

Ed

Stockden · 2nd Apr 2018, 8:27 pm

It sounds like a "Circuit Testing Ohmmeter". There are threads that may help here, here and here.

Hugh

johntech · 3rd Apr 2018, 11:38 pm

Hello
Thank you so much to everyone who has helped me sort out my little ohm meter ! This forum is one of the best it's quite amazing how people rally round to solve the problems of others.
Technology marches on and I am sure a lot of us probably retired as the trade went into decline.
Most service engineers could write a book of there experiences.
Happy days !
Thanks again John

Station X · 4th Apr 2018, 10:08 am

Was it just a case of using the correct leads then?

johntech · 4th Apr 2018, 9:37 pm

Hello Station X
Yes indeed it was !
An ohm meter with three terminals was confusing to my simple brain !

Station X · 4th Apr 2018, 9:50 pm

It would probably have confused me too!

Good to know it's fixed.

31st Mar 2018, 1:15 pm	#1
johntech Triode Join Date: Jan 2011 Location: Harrogate, North Yorkshire, UK. Posts: 34	Old Megger Test Meters Help ! Hello Folks I have recently been given a megger insulation tester (hand cranked type) and a low ohms meter the insulation tester is red and the low ohms meter green. The insulation tester works fine but I cannot fathom how to use the ohm meter. It has three terminals and a floating meter movement the battery is a pocket flash lamp type 4.5 volt. Has anyone got the instructions for this meter. I reckon could be 50-70 years old like me ! Any help gratefully received. Thanks John

31st Mar 2018, 2:27 pm	#2
Refugee Dekatron Join Date: Apr 2012 Location: Worksop, Nottinghamshire, UK. Posts: 5,554	Re: Old Megger Test Meters Help ! Have you checked the battery with a bulb? It may read all right with a meter but the loading from a low ohms range will need a fresh battery.

31st Mar 2018, 9:56 pm	#3
johntech Triode Join Date: Jan 2011 Location: Harrogate, North Yorkshire, UK. Posts: 34	Re: Old Megger Test Meters Help ! Thank you for your reply the battery is fine. The mystery is that the meter has 3 connections and somehow the meter must nullify the resistance of the test leads as there is no zero adjust pot. I'm sure there is an easy answer but what !

31st Mar 2018, 10:14 pm	#4
Refugee Dekatron Join Date: Apr 2012 Location: Worksop, Nottinghamshire, UK. Posts: 5,554	Re: Old Megger Test Meters Help ! That sounds like one with a single sense wire. It senses the resistance of one wire and assumes the other wire is the same resistance so the main leads need to be in good condition. Have you got any photos?

1st Apr 2018, 7:55 pm	#5
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,195	Re: Old Megger Test Meters Help ! Hi John, I have one of these somewhere, it has a twin probes, one of which has 2 wires, the other only 1. It looks to be as described above in that it compensates for lead resistance. It apparently came in 2 versions. The 2 wire unit had a battery button on the meter The 3 wire unit had a battery button on the 2 wire probe. Ed

1st Apr 2018, 9:35 pm	#6
johntech Triode Join Date: Jan 2011 Location: Harrogate, North Yorkshire, UK. Posts: 34	Re: Old Megger Test Meters Help ! Hello Ed & Co Thank you for your replies. There is no battery switch on the meter and there are no test leads either ! So I assume all three test leads should be identical wire. Presumably two leads are connected together which gives the meter its zero reading and the third lead plus the two others can then be used to take a measurement ? Do you think I am on the right track or talking rubbish as usual ! Its strange because these continuity "Meggers" were very common I can remember the electricians where I worked as a TV engineer having them and yet there is nothing that I can find on the net relative to them ! Perhaps someone somewhere has the original instructions we shall see. Best Wishes John

2nd Apr 2018, 8:07 pm	#7
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,195	Re: Old Megger Test Meters Help ! Hi John, I may have the instructions "somewhere" but I believe the 2 leads from the adjacent terminals are taken through a switch to turn the meter on. A probe goes from one of these wires. The other meter terminal goes to the other probe. If you are going to Golbourne on Sun I'll try and bring the meter along to show you. Ed

2nd Apr 2018, 8:27 pm	#8
Stockden Heptode Join Date: Mar 2008 Location: Forest of Dean, Gloucestershire, UK. Posts: 648	Re: Old Megger Test Meters Help ! It sounds like a "Circuit Testing Ohmmeter". There are threads that may help here, here and here. Hugh

3rd Apr 2018, 11:38 pm	#9
johntech Triode Join Date: Jan 2011 Location: Harrogate, North Yorkshire, UK. Posts: 34	Re: Old Megger Test Meters Help ! Hello Thank you so much to everyone who has helped me sort out my little ohm meter ! This forum is one of the best it's quite amazing how people rally round to solve the problems of others. Technology marches on and I am sure a lot of us probably retired as the trade went into decline. Most service engineers could write a book of there experiences. Happy days ! Thanks again John

4th Apr 2018, 10:08 am	#10
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: Old Megger Test Meters Help ! Was it just a case of using the correct leads then? __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

4th Apr 2018, 9:37 pm	#11
johntech Triode Join Date: Jan 2011 Location: Harrogate, North Yorkshire, UK. Posts: 34	Re: Old Megger Test Meters Help ! Hello Station X Yes indeed it was ! An ohm meter with three terminals was confusing to my simple brain !

4th Apr 2018, 9:50 pm	#12
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: Old Megger Test Meters Help ! It would probably have confused me too! Good to know it's fixed. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.