Operating temperature PXI Cards

[s.h._tech]

Hello everyone,

I have a PXI 1078 System with a few PXIe Cards in the following order

• PXI4322: Analog outpot
• PXI5433: waveform generator
• Empty
• PXI8513: CAN
• PXI8433: Rs232
• PXi6220: AI/DIO

I recently installed the FGEN driver for the waveform generator and after starting MAX and checking the device I noticed that the operating temperature of the PXI5433 was 78C°. The neighbour card PXI4322 was 73°C, all others were around 45°C.  In the datasheet the normal operating temperature of should be between 0-55°C.

The PXI is located on a free standing laboratory table. No walls nearby and the next equipment is at least 0.5m away.

Why is the temperature that high? Can I still safely operate my system?

Over lunch I systematically change the cards and check if the temperature goes down to identify if one of the cards generate the heat increase. 

[s.h._tech]

I removed the Waveformgenerator Card and the PXI4322 now shows a Devicetemperature of 65°C. 

After studying the datasheet I noticed some vocabulary that I do not understand correctly. In the datasheet is a value of the operating voltage from 0-55°C, where MAX shows a devicetemperatur. 

Are this the same temperatures?

Or is the devicetemperature just an internal value for processors/ ADC and other hardware?

[GPIB_Guru · Accepted solution]

You may be confusing ambient with operating temperature. The hardware is designed to run up to certain operating temperatures, which will exceed the ambient (room) temperature. The hardware is generally spec'ed to run at given ambient temperatures so that the heat generated during runtime (which will be essentially be added to the ambient) doesn't exceed the actual hardware thermal limits.

I don't know what the maximum operating temperature of the 5433 is, but someone else may.

[s.h._tech]

I was thinking the same. My understanding of operating temperature is the temperature of the environment. 

It would be nice to have a recommended value in the datasheet for the 'devicetemperature'. I also contacted out NI-Technician and he told me that this values usually are a mean value of temperatures across the PCB. As long as the values are below standard chip limits (~125°C) this should be fine.

We placed two CPU-Fans on top of the chassis since the top of the and the bottom plates are grated. Now there is a nice warm breeze on the bottom. This should not be necessary but the hardware is too expensive and I may be to cautious.

I will repeat some calibration measurement to see if the overall behavior changed.