There are a couple of differences. Thermally-driven sensors can be somewhat
harder to burn out accidentally, because they use a resistive element
instead of a tiny diode chip. You won't tend to fry them with ESD on the
workbench, for example. For the same reason, they can theoretically look
like a better 50-ohm load than a diode sensor, although I don't believe the
difference matters much in the real world.
The biggest drawback to thermocouple-based sensors that I've personally
noticed is that they don't work well at low power levels, where a zero-bias
Schottky diode excels. With a resistor-thermocouple sensor, it can take
several seconds for a power reading near the bottom end of the range to
settle down. They really don't do well below -20 dBm.
A thermal sensor will also give true-RMS power readings for all waveform
shapes, for obvious reasons, while readings taken with a simple diode
detector will be most accurate for clean sinewaves.
I *believe* the 435/436 wattmeters can use both types of elements, but don't
quote me on that...
-- john, KE5FX
toggle quoted message
Show quoted text
-----Original Message-----
From: hp_agilent_equipment@...
[mailto:hp_agilent_equipment@...]On Behalf Of test_right2000
Sent: Friday, January 19, 2007 6:54 AM
To: hp_agilent_equipment@...
Subject: [hp_agilent_equipment] Diode sensors or thermocouple sensors
Very new to power sensors and was wondering if someone had the time to
explain a few things with me. 1)When and why would you select one type
of sensor over the other? 2)Do both sensors work with the same
wattmeter? 3)Does the wattmeter need to be setup differently according
to the type of sensor used? I am a Ham and work with test equipment and
radios mainly below 1 Gig. Looking at buying HP, Boonton or Marconi
digital wattmeter. I am sure I have more questions but this
information would be of great help. Thank you??????..Jim
hp_agilent_equipment-unsubscribe@...
