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Author Topic: Relatively Measuring (REL)  (Read 1121 times)
AD7C
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Posts: 81




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« on: March 03, 2011, 03:31:24 PM »

So I have a decent (cheap) digital voltmeter and it has served me well, however, I have never used one feature because... well... I have no clue what it means.  The manual is all Chinese so no help there. 

There is a button labeled PRL and when pressed (in just about any mode: DCV, DVA, ACV, etc) it puts the word REL on the screen.  After some digging today I found another manufacturer that has a similar button on a similar meter but the only explanation they give is "Press PRL Button to activate the relatively measuring (REL) function".  Nothing more. 

What is the world is "relatively measuring".  A feature built in for Einstein?

73,

Rich
KE7SAK
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N3OX
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Posts: 8847


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« Reply #1 on: March 03, 2011, 04:07:52 PM »

I don't know for sure, but here's my guess and you can test it.

Measure a voltage, say 12VDC.

While the voltage is displayed on the screen, press PRL.

My guess is that the meter will go to zero and REL will appear.

Now measure ground.  Does it read negative 12VDC?

My guess is that the meter memorizes the voltage value it sees when you press the PRL and subtracts that from subsequent measurements, allowing relative measurements with respect to some voltage.  If you press PRL when you're not measuring anything, then you're measuring relative to zero and nothing changes.

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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
AD7C
Member

Posts: 81




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« Reply #2 on: March 04, 2011, 07:26:37 AM »

Yep.  That's it exactly.  Tested with 12v as the reference and then on a 9.6v battery and got 2.4v as the reading. 

Thanks!

Rich
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