[Hallicrafters] 1000 ohm/volt VS 20K/volt VTVM voltage measurements

[Richard Knoppow]

    The problem is that the difference depends on the resistance of the 
circuit. For very low resistance circuits there is little difference but 
when the resistance is high the difference can be considerable.  In the 
SP-600 even the B+ will read a little differently for the two meter 
resistance values.
    I can't remember if it was Hammarlund or someone else that specified 
a Weston voltmeter for the measurements. It took a lot of searching to 
find that particular model and its specs. Turned out to be 1000 
ohms/volt. The lower resistance divider string can be used with a less 
sensitive meter (i.e. cheaper) so was very common. 20,000 ohms/volt 
meters began to be popular about when television sets showed up because 
they were necessary in order that the meter not disturb the circuitry 
too much. Around the late 1950s some very high resistance meters came on 
the market; I have a Simpson 269 VOM with 100K ohms/volt for DC. On the 
higher ranges this can be higher than a typical VTVM but I don't like it 
much because of the layout of the scales. My most used meter is still a 
Triplet 630A.

On 5/26/2017 2:39 PM, Jammer via Hallicrafters wrote:
> 
>   Richard Knoppow said (emphasis mine):
> 
> 
>   readings made with the1000 ohm/volt meter are significantly different from those you will get with a 20K ohm/volt meter or a VTVM
>   aHa!, I thunk so, thanks mucho for the confirmation and clarification,
> Richard; s'good to have these factoids on hand. <G>
> 
> Thanks!  73 de Terry Bakowski KC9KEL, on-air someday


-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL