[Elecraft] Supply voltage and diode drops....

Wed Jun 18 11:28:06 2003

Hi

The main problem with fixing the voltmeter in firmware is the diodes do not 
all have the same voltage drop and the voltage across the diode will vary 
with the current through the diode and the temperature of the diode. The 
diode will drop maybe .65 volts at 200 ma but may be up closer to a volt at 
2 amps. There is also a small drop in the self resetting fuse and it will 
vary with the current also.

Don Brown
KD5NDB

----- Original Message ----- 
From: "Dave Jewell" <[email protected]>
To: <[email protected]>
Sent: Wednesday, June 18, 2003 10:08 AM
Subject: Re: [Elecraft] Supply voltage and diode drops....

> In-Reply-To: <[email protected]>
> Yeah, that makes sense, Harry.  Although I suppose one could argue that
> since you need to change a jumper on the control board (P7) to enable the
> voltmeter, you may as well change a menu option to disable the automatic
> addition of 0.65 to the voltmeter at the same time.  If there was a spare
> input on the PIC, this could be done automatically with a few more parts.
>
> Cheers,
> Dave GW0LUA
>
> -------------------
>
> > From: Harry Yingst <[email protected]>
> > Subject: Re: [Elecraft] Re: Elecraft digest, Vol 4 #205 - 42 msgs
> > Because then the volt meter would be off and no good for other purposes
> > unless you subtracted that fixed ammount from the reading.
> > it is far easier the way it is
>