PMEL Forum

K Sections => K3/4 - Waveform Analysis & RF Generation => Topic started by: radhiabouras on 11-09-2017 -- 17:55:53

Title: thermistor mount calibration
Post by: radhiabouras on 11-09-2017 -- 17:55:53
Can a Tegam 1830A power meter be used to calibrate thermistor mounts.
Title: Re: thermistor mount calibration
Post by: briansalomon on 11-10-2017 -- 14:53:38
No. Power meters are used with thermistor mounts and other power sensors to measure RF power and are not capable of verifying the performance of a power sensor.

Because it functions without a referncing 1mW source like other power sensors the 478A is typically used to verify the 1mW reference output of power meters.

This means that in most labs the 478A represents a large part of the traceability for all absoloute power measurements.

I wouldn't send that instrument anywhere but Keysight.
Title: Re: thermistor mount calibration
Post by: kuroi1185 on 11-16-2017 -- 04:45:15
Yes. You can use the Tegam 1830A in 432 Compatible mode to calibrate thermistor mounts. I think that there is some more information about this on Tegam's website or in the 1830A's manual that can be found with a simple search. 
Title: Re: thermistor mount calibration
Post by: briansalomon on 11-16-2017 -- 16:06:46
Not to put too fine a point on it.....

Here is a lick to the 1803A calibration/service manual  https://www.tegam.com/wp-content/uploads/2015/10/1830A-Manual-Rev-L.pdf

If you look on page 5-1 it shows that this manual deals with "calibration of the 1830A" and makes no mention of calibrating a thermistor mount. If we are in doubt, Tegam customer service will be able to clarify.
Title: Re: thermistor mount calibration
Post by: CalibratorJ on 11-20-2017 -- 15:26:59
An 1830A can be used in the calibration of a thermistor mount. It has to be connected to a meter to function.

Is it the standard? No.

I would personally advise to use the same type of meter that the customer is using the thermistor mount on in the calibration of the mount. If a customer uses an 1830A, the lab performing the cal should as well, likewise for a 432A or the N432A (or whatever Keysight is calling it), same if the customer is using it with a Tegam bridge or a Type IV power meter. The differences are minimal, but they are there - trust me, we have looked at it in great detail recently.

And there are labs out there that are capable of calibrating thermistor mounts, even 478A Option H75s, other than the OEMs (Keysight and Tegam, to name the big(ger) 2). Doesn't mean you should send it to all, or even many, of the companies that "claim" to be able to calibrate them without scrutinizing their uncertainties, but they do exist.
Title: Re: thermistor mount calibration
Post by: microwave-kevin on 01-19-2018 -- 04:43:16
Excellent replies but I would ass one caveat.

If the mount is a 8478 type with internal temperature compensation bridge better to do it with the bridge disable. The temp comp bridge adds a small error uncertainty, most national labs calibrate with the bridge disabled

aloha
Title: Re: thermistor mount calibration
Post by: briansalomon on 01-19-2018 -- 13:04:09
I do see value in using more than one vendor for a given discipline and agree Keysight is not the only capable lab out there. We definitely appreciate the value of having multiple vendors.

Title: Re: thermistor mount calibration
Post by: microwave-kevin on 02-07-2018 -- 05:14:01
NMI's calibrate them, whats interesting is to see how people use the thermister as a standard, typically they use a "feed-through" with a power splitter. I have even seen "Primary" labs calibrate a feed-through without access to all three splitter ports.... like they thought source match was 1,1...2,2 and 3,3 with everything terminated..... No concept of Source Match