# Typical and Maximum Heat Load for PXI and VXI Controllers?

Updated Aug 22, 2018

## Reported In

### Hardware

• PXI Controller
• Controller for VXI

## Issue Details

I have a system in which I need to know the heat load for National Instruments controllers because the system is very sensitive to different heat levels. Where can I find that information?

## Solution

For a conservative estimate of how much heat is given off by any PXI or VXI controller, we first must assume that the entire power draw for the controller is transferred into heat. Even though there is energy loss in the conversion from power to heat, we will use this assumption for the conservative estimate.

To find how much power a controller will produce, we must use the following equation:
Power = Voltage x Current

We can then apply this equation to the electrical specifications found in any PXI or VXI controller's manual.

For example, under the Electrical section on page A-2 of the PXIe-8840 User Manual, it states that the PXIe-8840 outputs 5 different voltages. Each voltage has a typical and maximum current that it can supply at that voltage. By applying this equation, we can find the typical and maximum heat loads for that controller.
(3.3V * 1.03A) + (5V * 1.33A) + (12V * 2.87A) + (5V * 0.20A) = ~45 watts generated, an estimate for typical use.
(3.3V * 1.65A) + (5V * 2.48A) + (12V * 5.16A) + (5V * 0.41A) = ~82 watts generated, an estimate when the controller is under full load.