Re: Experimental Help - Terry?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<Goinbonkers-at-aol-dot-com>
>
> The hot wire sensor is one commom way to measure RF power.  I have some
> literature on it.  I'll try to dig it up.
> Mike
> >
> > Might be a 'hot wire' (second gen) type sensor.

I'd say that a thermal detector is THE way that RF power is measured
(accurately)... Whether a bolometer or thermistor... The fancy detectors use
balanced circuits that hold the detector at constant temperature with a DC
current. The amount the DC current decreases (and the resistance..) tells
you how much power is being dumped into with the RF.  Uncertainties in this
sort of sensor are:

1) How accurately you measure the DC current
2) How accurately you hold temperature (this one's easy, because it's
basically a nulling to hold it at a zero, rather than actually measuring
something...)
3) RF mismatch.. The RF power has to really get into the load, and not get
reflected back.  The connectors are a problem here..

But, in any case, all those HP power meters use thermistor heads...