Using a HP 8477A Calibrator to test a HP 432A Power Meter

[@georgeveropoulos2489]

hi very nice! i want to ask you in any new meauser the power meter must calibrate ?

[@tgsoapbox]

If the meter is new, then typically all you need to do is to confirm that it passes the operator check (assuming that the manufacturer has included a calibration step in its production). If you want to be very sure or the meter is second hand, then you'd run it through its performance checks. If you've done any work on it, then you should run it through the adjustments process before use.

[@w8biatvrepeater638]

I am wondering why, when you started, you did not initiate the fine zero switch as the meter movement was starting below zero?

[@tgsoapbox]

I must have missed doing that as you're supposed to when using the 432A.

[@tgsoapbox]

Actually, just looked at the video - Are you talking about the zeroing at the start of the video around 2:24? If that is what you're referring to then this action isn't part of the test when using the 8477A calibrator - Using the zero knob on the calibrator takes care of that operation. Fine Zero is an automatic control that helps keep the bridge balanced when RF power isn't applied.

[@davidv1289]

Interesting video, thanks for sharing. I'm not sure I understand the difference between open circuit and closed circuit meters, is that a difference between thermistor sensors and diode sensors ?

[@tgsoapbox]

Yes - The 8480 series sensors are basically "open" in the sense that they need the power reference to set the measurement (The 'open loop' designation is a play on control theory with the 'open loop' systems needing a stake in the ground to work). "Closed" ones are like the 478A Thermistor which can make a measurement directly without referencing it to another value.

[@davidv1289]

Thank you for the reply. I've used power meters for many, many years as a radar technician - almost exclusively the diode sensor type - and never noticed the (now) obvious difference between the older thermistor mount meters and the newer diode meters - no calibration source on the thermistor meters! There is no need to "calibrate" the thermistor sensor before use. Still learning ! My choice for my retirement bench was the HP 437B with a 8482A and a 8484A sensor.

[@PapasDino]

Good on Keysight for still supporting this gear which I'd imagine is actually still used in many shops. What was the magnitude of what they got for doing that for you?

[@tgsoapbox]

All up, between the 3458A, 8477A & 432A-H76 it was around $2.5K but it is important to get these things checked when you buy them off eBay - I don't think I'll be doing that yearly as I don't need traceability. I'll do a standards cal on the 3458A every 3 years to see how it is drifting though.

[@TheDefpom]

Noticed the needle is twitching around a little on the first test, I wonder if one of the controls are a bit dirty? Probably the calibrator output, due to the voltmeter jumping around a bit too.

[@tgsoapbox]

I think it is my radio mic - I noticed the needle not moving when I was quiet.

[@danishnative9555]

You have been conspicuously absent lately. Must be playing rugby with the schnauzers.