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| Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets. |
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30th Aug 2014, 9:32 am
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#1 |
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Rest in Peace
Join Date: Mar 2006
Location: N.W. Oxfordshire(Chipping Norton)
Posts: 7,306
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LF Choke DC resistance reads higher with DMM than analogue meter - why?
Checking a LF choke the other day, I first measured it with my DMM and it read about 900 ohms, then with a Philips Analogue meter, which read about 400 ohms. Why would there be this difference? The service sheet for the Roberts valve radio to which the choke is fitted specifies about 380 ohms, so the analogue reading is correct, but, as stated, the difference puzzles me!
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30th Aug 2014, 9:53 am
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#2 |
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Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,896
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Re: LF Choke DC resistance reads higher with DMM than analogue meter - why?
The DMM test is pulsed. Often done to save battery life
David
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Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done |
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30th Aug 2014, 12:15 pm
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#3 |
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Guest
Posts: n/a
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Re: LF Choke DC resistance reads higher with DMM than analogue meter - why?
Well I never knew that, you learn something everyday.
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30th Aug 2014, 12:59 pm
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#4 |
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Dekatron
Join Date: Jun 2009
Location: Staffordshire Moorlands, UK.
Posts: 5,273
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Re: LF Choke DC resistance reads higher with DMM than analogue meter - why?
My autorange DMM won't even settle between ranges on some inductors. Using the manual range over-ride fixes that.
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Kevin |
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