Refurbishing a Heathkit IM-13 VTVM. Originally had zinc/carbon battery which I understand had a voltage of 1.55 and to calibrate the instrument, the meter has a red dot at the 1.55 spot and you would have tweaked a pot to align the needle with the dot.
What is available is an alkaline battery which has a voltage of 1.60; I am thinking that I need to calibrate the instrument by tweaking the pot to line up with 1.60 volts (not the red dot 1.55 volts).
Your thoughts and/or comments must welcome. I can attach a schematic if that helps.
What is available is an alkaline battery which has a voltage of 1.60; I am thinking that I need to calibrate the instrument by tweaking the pot to line up with 1.60 volts (not the red dot 1.55 volts).
Your thoughts and/or comments must welcome. I can attach a schematic if that helps.
Can't answer directly, but with 1% resistors cheap and common these days, try it. Then see if your resistors measure up correctly.
There is calibration and then there is just daily use. Each time you start a measuring session, don;t you generally have to short the leads and turn the set-zero control anyway? They were not expecting a fresh battery in those meters every day. That zero control was there to compensate for battery variations.
As an aside, we mostly prefer alkaline batteries for performance reasons, but aren;t plain old common batteries still on the market? Usually called "heavy duty" or some such.
There is calibration and then there is just daily use. Each time you start a measuring session, don;t you generally have to short the leads and turn the set-zero control anyway? They were not expecting a fresh battery in those meters every day. That zero control was there to compensate for battery variations.
As an aside, we mostly prefer alkaline batteries for performance reasons, but aren;t plain old common batteries still on the market? Usually called "heavy duty" or some such.
Oh wait. This is not about calibrating the ohms scales? They are using the 1.55v as a voltage standard to calibrate the DC volts scale against? For that all you need is a DC voltage you know to be a certain value then set this meter to it. it may not have the convenience of aligning to a dot, but should work just as well. If your flikes agree on some voltage, be it a battery or something else, then use that as a standard and set the Heath to it.
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