Input bypass circuit with linearization (XTR112/XTR114)

As shown in the figure, the long wire current loop transmission of this circuit will introduce radio frequency (RF) interference. RF energy will cause errors in the sensitive XT11l2/114 input, which will be manifested in the instability of the loop current or input line current. If the RTD sensor is at a long distance, interference will be introduced at the input of XTR112/114. If the transmitter and sensor are connected by short wires, the interference will come more from the connection wire of the current loop. The method to eliminate interference is to add a 0.01μF bypass capacitor filter at the input to reduce or eliminate interference. Connect the common point of these bypass capacitors to the IRET terminal. Although the DC voltage at the IRET terminal is not zero, it is the "ground" of the transmitter. In addition, connecting a 0.01μF capacitor between the V and Io terminals will help minimize output interference.