Each DSCT47 thermocouple input transmitter provides a single channel of thermocouple input which is filtered, isolated, amplified, linearised, and converted to a process current output. Signal filtering is accomplished with a five-pole filter, which provides 85dB of normal-mode-rejection at 60Hz and 80dB at 50Hz.
An anti-aliasing pole is located on the field side of the isolation barrier, and the other four are on the process loop side. After the initial field-side filtering, the input signal is chopped by a proprietary chopper circuit. Isolation is provided by transformer coupling, again using a proprietary technique to suppress transmission of common mode spikes or surges.
Linearisation is achieved by creating a non-linear transfer function through the module itself. This non-linear transfer function is configured at the factory and is designed to be equal and opposite to the thermocouple non-linearity.