National Instruments SCXI-1321 Offset-Null and Shunt Calibration Terminal Block

The NI SCXI-1321 (Part Number: 777687-21) is ideal for applications with strain gauges, RTDs, or thermistors. This model is well-suited for temperature or voltage applications with a high quantity of channels. This High-Voltage Terminal Block is shielded to allow swift, reliable signal connections. The SCXI-1321 brings nulling and shunt calibration to SCXI-1121 strain gauge applications but can only be used with the SCXI-1121 module revision C or later. There are 18 screw terminals on the NI SCXI-1321.

There is also a front-panel trimming potentiometer, which enables the user to manually null out the offset voltage or bridge transducers. Every channel has shunt calibration circuits that can be controlled as a group via software. The user can also trigger a switch on the SCXI 1321 Terminal Block to link a 301 k Ohm shunt resistor in parallel with the strain gauge. The nulling and shunt resistor on the Terminal Block are socketed, so they can be customized by the user with ease. The device has a maximum field wire gauge of 26-16 AWG, a cold junction sensor output and accuracy of ±10 mV/˚C and 1.3 °C respectively. It has a maximum working voltage of 300 V (CAT II).

Offset nulling is a hardware nulling process with Wheatstone-bridge transducers that have an initial offset error. Fixing this error will increase measurement preciseness. The nulling circuitry on the SCXI-1321 will work with quarter-bridge, half-bridge, and full-bridge strain-gauge arrangements. Every channel has separate nulling circuitry, as well as a designated trimming potentiometer. For example, Channel 0 corresponds to Potentiometer R1. Channel 1 corresponds to Potentiometer R2. Next, Channel 2 corresponds to Potentiometer R14. Finally, Channel 3 corresponds to Potentiometer R15.

It has a recommended operating temperature range of 0 to 50 °C, a storage temperature range of –20 to 70 °C, and a non-condensing relative humidity range of 10 to 90%. The NI device is designed to comply with the following electrical safety standards: IEC 61010-1, EN 61010-1, UL 3111-1, UL61010B-1, and CAN/CSA C22.2 No. 1010.1.

SCXI-1321 Obsolete Status has been announced by National Instruments, but the Terminal Block will still be available for purchase and repairs by Apex Waves.