[Elecraft] K2 voltage and Current display

Mon May 5 10:26:01 2003

In addition to the drop reverse voltage blocking diode The voltage reading 
can be off due to two other factors:
The precision resistors in the voltage divider may be off a little and 
still be within 1%. If they are both "off" in different directions then the 
difference can have more than a 1% effect. Also the DVM does not measure an 
"absolute" voltage it actually measures the voltage from the voltage 
divider relative to the micro controller's 5Volt supply voltage. If that's 
not exactly 5.00Volts than the reading are off by the difference. In my 
case I found about a 1/2% error in the resistors in the divider circuit and 
about 2.2% error in the 5V supply giving a 2.7% error which is almost 0.4V 
at 13.8 volts.
73
Steve Holton N1NB
K2  #2646 & 2843

At 04:01 5/4/2003 -0400, [email protected] wrote:

>From: Jerry Rheinschmidt <[email protected]>
>Subject: [Elecraft] K2 voltage and Current display
>
>Hi All,
>
>I am building a K2 and think I may have a problem.  I have 14.2vdc on
>J3 the dc input jack on the back of the K2.  On the cathode side of
>D10 I have a voltage drop of 0.3 vdc which is normal.  My question is
>I have another 0.3 vdc voltage drop reading on the display.  The
>display reads 13.6 vdc and 0.160 amps with LCD set for day.  When I
>switch to nite the current is 0.2 amps.  I think this is marginal but
>is it ok?
>Jerry
>WA0BFD
>
>K2 #2655