[time-nuts] OT: Power level reference

[Lux, Jim (337C)]

There was a special issue of IEEE proceedings about 30 years ago on just
this subject.  I'll see if I can find the date (it's on my desk at work)

Basically, you always wind up going back to some sort of calorimetric
standard: some sort of load which you measure the temperature rise of, and
that you can calibrate the mass/thermal properties of by some sort of DC
replacement (since it's straightforward to accurately measure voltage and
current).

Be aware that this is only part of the game.  There's also the whole
mismatch issue to deal with, and for microwave frequencies, the mismatch
uncertainty often dominates over the uncertainty of the power reading.

You can also read up on the NIST Type IV power meter.


On 12/1/09 12:17 AM, "Poul-Henning Kamp" <phk at phk.freebsd.dk> wrote:

> In message <c793a5fe0911302041p1bcde3e0p13deca7efe9c9cad at mail.gmail.com>,
> Josep
> h Gray writes:
> 
>> We all have our various highly accurate frequency and perhaps time
>> references. Is there a relatively simple and inexpensive method of
>> making an accurate RF power level reference? If so, then what do we
>> calibrate it with, not already having such an accurate reference?
> 
> I investigated that some time ago, in relation to calibrating the
> HP3458A.
> 
> The way you do it, is with a thermal converter.
> 
> I've been playing around to see if instead of a thermocouple it would
> be possible to do the sensing by infrared light, and it looks possible
> but I have not spent enough time to nail it usably yet.
> 
> --
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> phk at FreeBSD.ORG         | TCP/IP since RFC 956
> FreeBSD committer       | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.
> 
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