Changing the Fan Mode Programmatically of a PXIe Chassis
Updated Feb 12, 2020
Certain National Instruments PXIe chassis' have a fan speed selector switch on the back of the chassis which allows for switching the fan speed between Auto and High. In Auto mode the chassis fan control system uses intake air temperature as the input for controlling the speed of the fans, which provides improved acoustic performance. High fan speed mode on the other hand provides for maximum cooling performance, but decreased acoustic performance. Some use cases may benefit from having more control of the fan mode programmatically. Details for how to do this are contained in the rest of this document.
Programmatic fan control is currently supported in the following National Instruments' PXIe Chassis: PXIe-1085, PXIe-1086, PXIe-1066DC, PXIe-1084, and PXIe-1095.
A feature was introduced in NI System Configuration 16.0 to allow users to programmatically change the fan speed control to a third mode, Safe Manual mode, on the PXIe-1085, PXIe-1086, and PXIe-1066DC chassis. Safe Manual mode allows the user to set a speed, in rpm, at which the fans should run. Your chassis' fan speed selector switch must be in Auto mode in order to utilize this mode. If the speed selector switch is set to High, the fans will continue to run at High regardless of the configured Safe Manual settings.
Note: If you set the speed below the maximum supported by your chassis, the fans will run above the user-defined speed if the intake air temperature necessitates it.
Use of this feature requires the following two properties within the System Configuration API:
*The PXIe-1085 supports a maximum fan speed of 4600 rpm. The PXIe-1086 and PXIe-1066DC support a maximum fan speed of 3800 rpm.
Use the NISysCfgGetResourceProperty and NISysCfgSetResourceProperty functions to get or set the current value of these properties. Call NISysCfgSaveResourceChanges after setting these properties to write and save the property changes to the device. Once saved, these settings will persist between reboots. See the NI System Configuration API help that gets installed with the software for more information on using these functions.
Similar functionality was introduced for LabVIEW in NI System Configuration 18.0. You can take advantage of this functionality by dropping a System Configuration Property Node onto the Block Diagram of your VI, and finding the appropriate properties in: System Resources >> Fans >> PXI ChassisFan Control.
Upgrade your host PC or controller to NI System Configuration 16.0 or later (or NI System Configuration 18.0 or later for LabVIEW functionality). If programming in C, make sure to enable the LabWindows/CVI (C) API support in the installer tree:
If programming in C, include nisyscfg.h and nisyscfg_pxi.h in your source code. These files are installed at: C:\Program Files (x86)\National Instruments\Shared\ExternalCompilerSupport\C\include\