How hot should a PXI chassis get?

[toddy]

I have several PXIe-1071 chassis running with either 8133 or 8135 controllers. I have the fans on the chassis set to Auto via the switch on the back. On Friday, one of these chassis was 65°C on the top of the case (above the controller) but the fan wasn't going flat out. Another 2 chassis were about 55°C, again the fans were not running very fast. 2 more of the chassis were in the mid 30s.

All of these chassis are in the same, air conditioned room.

I would have thought that if the outside of the chassis is getting above 50°C, the fans should be going flat out, as surely the temperature inside is much much hotter?

The chassis have space all around them for ventillation, so it's not that causing the variance in temperature. They are all running more or less the same code, and using approx. 60% processor load (on the 8133s)

Any insight would be appreciated.

Toddy.

[Lucas.]

Hi Toddy,

According to the data sheet of the product (link below) the operating environment should be 0 to 50 degrees so it seems you are pushing that limit. 

http://sine.ni.com/ds/app/doc/p/id/ds-257/lang/en

I would advise that you turn the FANS on high to ensure that there is sufficient cooling. This is the recommended setting in the manual. Auto is designed to minimise acoustic disturbance. 

http://www.ni.com/pdf/manuals/373011d.pdf

Have you got the chassis stacked on top of each other ? 

Have you looked at the temperature of your controller using MAX  ?

[toddy]

Hi Lucas,

Thanks for responding. The ambient temperature around the chassis is 23°C, so they should easily be able to keep cool, the hot temperatures measured on the outside surface of the chassis are being generated internally. Unfortunatley there's no way of seeing the internal temperature of either the chassis or the controller as far as I can see in MAX. I think this is a limitation of using the PXIe-1071 chassis.

The chassis are not stacked on top of each other - there is at least 150mm of free space above the chassis.

I understand that turning up the fans to full will make it run cooler, but I would have thought that the whole point of the Auto setting is that it uses as much fan as it needs to keep it to a certain temperature. We don't run our PCs with full fans on all the time!

Do you know what temperature the Auto fan control is aiming to maintain?

Thanks,

Toddy

[Lucas.]

Hi Toddy

The recommended setting is High for this paritcular chassis and Auto is suggested to be used to minimise acoustic disturbance whereas a PC typically doesn't require you to set the fan speed to high. 

What cards do you have in your chassis  (Some cards such as High speed digitzers often get very hot so the fan should be on the High setting) ?

If you have an appropriate card in your chassis you may be able to access the card temperature (see the link below on how to do this ) 

http://digital.ni.com/public.nsf/allkb/5222222FF438914B86256B0C000347C6 - Accessing on-board temperature of DAQ Device. 

I'm afraid I don't know the temperature that the Auto control is trying to maintain but I found a Knowledge Base article on using slot blockers to aid cooling in a PXI chassis and I thought this may of use to you. 

http://digital.ni.com/public.nsf/allkb/F443407138DBCE2286256C8600584E96 - Improving cooling with slot blockes. 

Let me know if you have any more questions. 

[Lucas.]

You may also be able to use distributed system manager to access the information about your device. 

You could also use a 3rd party piece of software to access the CPU temperature of your controller. You can do these by doing a quick look on google. "Real temp" was one that showed up when I searched online. This is a 3rd party software so NI doesn't support it but you should be able to find some usefull information about your controller so see what temperature it is operating at. 

I hope this helps!