Chapter 3 Hardware Overview
© National Instruments Corporation 3-3 NI PXI-8250 User Manual
System Monitoring Architecture
With the NI PXI-8250, you can simultaneously monitor intake
temperature, fan speeds, and power supply levels of your NI PXI chassis.
This information allows the user to achieve a higher level of system
performance reliability. Once the first set of data is processed, these status
parameters will also light up the top six LEDs on the front panel. The LEDs
light either as green if the status parameter is in range, or red if the
parameter is out of range. Refer to the Front Panel LEDs section for more
information on the LEDs.
A custom FPGA on the NI PXI-8250 communicates with the power supply
module of the chassis for status information. Upon boot-up, the
NIPXI-8250 waits 7 seconds for the chassis sensors to acquire their first
value. Once the wait period is over, the NIPXI-8250 begins acquisition of
the first full set of data from the chassis. The status information is then
obtained every 5 seconds automatically in hardware until the controller is
rebooted or shutdown.

Voltage Rail Level Monitoring

The NIPXI-825 0 module monitors the +5 V, +3.3 V, +12 V, and –12 V
rails delivered by the power supply shuttle within an accuracy of ±100 mV.
The data from the +5 V and +3.3 V rails have two significant figures, while
the data from the +12V and –12 V rails have one significant figure.
Each power rail has its own status LED on the front panel to reflect the
current status of the rail. If the voltage rail is within ±5% of the common
chassis specification, then the LED will light green. Otherwise, the LED
will light red.
The voltage rail level monitoring feature of the NIPXI-8 250 reports when
a voltage rail goes out of spec. This information is useful in ensuring proper
operating conditions for each PXI module.

Temperature Monitoring

The NIPXI-825 0 provides monitoring of the single intake thermistor
located in the power supply shuttle of the PXI chassis. The reading from the
thermistor (0–50 °C) is compared to the operating range of the chassis. If
the reading is in range, the TEMP LED will light green. Otherwise, it will
light red. All temperature measurements are reported in Celsius and are
accurate to within 1°C of the actual intake temperature.