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Where would you measure temperature inside a VNA?

Question asked by drkirkby on May 11, 2019
Latest reply on May 15, 2019 by drkirkby

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I know the FieldFoxes, and believe the PNA-Xs, have a temperature sensor(s) inside. Where are those sensor(s) located?

I have a small lab at home, and can't run the air conditioning 24/7, so its fairly obvious that my 8720D drifts more than it might otherwise do. I'm trying to quantify the drift, and see if it follows room temperature, or the internal temperature. I was thinking of adding a temperature sensor - probably a pt100, as the are more convenient to use than a thermocouple for me.

I'm trying to think where might be the best place(s) to measure the temperature. I'm guessing the receivers might be the most critical - obviously measuring the temperature of the CPU is not going to be as useful.

Dave

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am95405

May 13, 2019 8:19 AM

Hi Dave,

I don't know where FieldFox's sensors are exactly physically located, but I know we have multiple sensors. See page 82 of the Service Guide.

http://literature.cdn.keysight.com/litweb/pdf/N9927-90003.pdf

Afsi

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daras

May 13, 2019 11:29 AM

Unless your room gets really hot or really cold, then the temperature inside your instrument is not going to be greatly impacted by the ambient room temperature as long as you turn on your VNA and let it warm up for 30 to 60 minutes before making any measurements or calibrations. however, the ambient temperature will have much greater impact on the cables, the calibration standards and any other adapters or accessories that are outside of the VNA. so if you want to keep track of temperatures, you need to keep track of it outside of the box close to where you have your cables and DUT. Note the ambient temperature at the time of the calibration and when you are making the measurements. I don't have the specs for eh 8720D, but for PNAs, calibrated system performance is within specifications as longs as the ambient temperature at the time of the measurement is within 1 degree C of the temperature at the time of calibration.

But to answer your original question, the temperature sensors inside PNA's is on the mixer assemblies.

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drkirkby @ daras on May 15, 2019 1:01 PM

Thank you Dara and Afsi. I'm finding the 8720D is taking a lot longer to warm up than expected. I'm reckoning about 4 hours at an ambient temperature of 23 deg C. I will post a plot in a few days time which will show phase and exhaust air temperature vs time. I have the data now, but it was not collected in an optimal way, with about an hour missing, and a sub-optimal sensor.

I'd be interested in any comments following a graph.

Thank you for the comments Dara about the placement of the sensors. The 8720D has 3 samplers, so I'd probably put a thermocouple on each of them. At the moment I only have one temperature sensor, and no instrumentation to get data from any more sensors. But I intend getting a 34970A

34970A Data Acquisition / Data Logger Switch Unit | Keysight (formerly Agilent’s Electronic Measurement)

data logger switch unit with 34901A & 34902A input modules in the next few days. That should allow me to put more sensors around than I would ever hope to use.

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am95405 May 13, 2019 8:19 AM
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Hi Dave,

I don't know where FieldFox's sensors are exactly physically located, but I know we have multiple sensors. See page 82 of the Service Guide.
http://literature.cdn.keysight.com/litweb/pdf/N9927-90003.pdf
Afsi
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daras May 13, 2019 11:29 AM
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Unless your room gets really hot or really cold, then the temperature inside your instrument is not going to be greatly impacted by the ambient room temperature as long as you turn on your VNA and let it warm up for 30 to 60 minutes before making any measurements or calibrations. however, the ambient temperature will have much greater impact on the cables, the calibration standards and any other adapters or accessories that are outside of the VNA. so if you want to keep track of temperatures, you need to keep track of it outside of the box close to where you have your cables and DUT. Note the ambient temperature at the time of the calibration and when you are making the measurements. I don't have the specs for eh 8720D, but for PNAs, calibrated system performance is within specifications as longs as the ambient temperature at the time of the measurement is within 1 degree C of the temperature at the time of calibration.

But to answer your original question, the temperature sensors inside PNA's is on the mixer assemblies.
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- drkirkby @ daras on May 15, 2019 1:01 PM
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  Thank you Dara and Afsi. I'm finding the 8720D is taking a lot longer to warm up than expected. I'm reckoning about 4 hours at an ambient temperature of 23 deg C. I will post a plot in a few days time which will show phase and exhaust air temperature vs time. I have the data now, but it was not collected in an optimal way, with about an hour missing, and a sub-optimal sensor.
  
  I'd be interested in any comments following a graph.
  
  Thank you for the comments Dara about the placement of the sensors. The 8720D has 3 samplers, so I'd probably put a thermocouple on each of them. At the moment I only have one temperature sensor, and no instrumentation to get data from any more sensors. But I intend getting a 34970A
  
  34970A Data Acquisition / Data Logger Switch Unit | Keysight (formerly Agilent’s Electronic Measurement)
  
  data logger switch unit with 34901A & 34902A input modules in the next few days. That should allow me to put more sensors around than I would ever hope to use.
  Like • Show 0 Likes0
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Where would you measure temperature inside a VNA?

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