[Elecraft] DMM recommendations

[Don Wilhelm]

Chuck,

That is 5% of full scale with a recently calibrated slug.
Another way to look at that percentage of full scale is to consider a 
200 watt slug.  The error can be as large as 10 watts *anywhere* on the 
scale.  That is why I don't buy Bird wattmeters at hamfests unless it is 
cheap enough to send to a calibration lab.

At least a digital wattmeter retains its accuracy as a percentage of the 
reading - a very different specification.  Yes, +/- 20% is up to 40 
watts error at 200 watts, at 10 watts, the error is only 2 watts.

Many of the digital wattmeters like the Telepost LP100 can boast of 5% 
accuracy because they are calibrated with NIST tracable instruments.
Elecraft does use the LP100 at many of the technician workbenches.

73,
Don W3FPR

On 3/19/2018 3:39 PM, hawley, charles j jr wrote:
> Bird advertised and prints in the manual +/- 5% of full scale power. I remember some digital meters ARRL tested a few years back that did not do that well. Are your numbers something you experienced?
>