On 28 October 2016 at 01:05, Poul-Henning Kamp <[email protected]> wrote:
>The exception is the "cold mirror" type of sensor, which measures the > >dewpoint by cooling a mirror and bouncing a light off it to sense the > >temperature where dew condenses on it. Those are expensive, and they > >require maintenance to keep the mirror clean. > > And they are comparatively slow, last I saw one it could only do > a measurement every second minute. > I was just reading the Keysight forum on VNAs. Someone was having issues measuring a bit of waveguide 80 m long. Dr. Joel Dunsmore pointed out that humidity has an effect in waveguide. I'm guessing this is due to the change in permittivity in the air, which would be most noticeable near the cutoff frequency of the waveguide. That should change the magnitude of the reflection, not just the phase, so it might be a relatively cheap way to measure humidity. Just thinking aloud. I'm probably talking rubbish. Dave _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
