NI PXI-2501 Amplifier

The NI PXI-2501 has an amplifier with a gain of 1. This amplifier can be switched in-line before the COM0 signal and the AB0 signal. The amplifier helps decrease the settling time of the FET switch. The high-impedance amplifier isolates the FET from the resistance, capacitance, and inductance in the external wiring. This isolation decreases the resistance/capacitance time constant seen by the FET, which improves settling time.

The amplifier has an offset that should be calibrated for more accurate measurements. The calibration data can be stored into and retrieved from the EEPROM on the module. You can use NI-SWITCH to retrieve and store the calibration data. When the amplifier is used, the switch module becomes directional, where CHx is for signal inputs and COM0 or AB0 are for signal outputs.

The NI PXI-2501 also has an amplifier in the CJS0+ to COM0+ signal path. This amplifier in the cold-junction sensor signal path is used to improve settling time performance. It prevents the impedance of the cold-junction sensor from increasing the settling time when switching the CJS channel. As a result, when scanning thermocouples, the settling time for the cold-junction sensor channel should be about the same as for the channels with the thermocouples.