[time-nuts] Test Equipment

[Chuck Harris]

Bird wattmeters, such as the model 43 thruline, are far from
accurate devices.  They are spec'd to be +/- 5% of the full scale
reading of the installed slug.

That means for a 100W slug, the error band is +/- 5W!

If you happen to read 20W on the meter, the error band says your
true power could be anywhere from 15 to 25 watts!

As a comparison, an HP 432A wattmeter can achieve an ultimate
accuracy of +/-0.2% +/- 10uW.

-Chuck Harris

Don Latham wrote:
> Amtronix did tell me that the power measurements were off, according to 
> some folks who had compared them to Birds.  Of course the E's could be 
> calibrated. I don't have much below 30 MHz at present either.  I sense 
> that there may be enough around to warrant a Yahoo or Google group???
> Don
> 
> ----- Original Message ----- From: "Bob Camp" <lists at cq.nu>
> To: "Discussion of precise time and frequency measurement" 
> <time-nuts at febo.com>
> Sent: Monday, February 01, 2010 6:42 PM
> Subject: Re: [time-nuts] Test Equipment
> 
> 
>> Hi
>>
>> The big question in my mind about these is how well they do below 30 
>> MHz. Until I know I can trust them it down there, I'm not selling very 
>> much stuff.
>>
>> I have yet to find a data sheet from before 2000 when they shipped 
>> with the sub-800 MHz stuff enabled. I get the impression that the 
>> E8285's never quite did as well below 30 MHz as the 8920's do.
>>
>> Bob