Remote RTD temperature sensing-voltage and current output conversion circuit

When the distance between the RTD temperature sensor and the amplifier is relatively long,
issues such as the sensor's lead resistance and the vulnerability of the leads to interference cannot be ignored. The circuit shown in the figure can solve this problem.
    This circuit uses a voltage-4-20mA current converter XTR103. XTR103 is a dedicated signal processing circuit for RTD.
It integrates Rrl'D linearization circuit internally and expands the power supply voltage range to +9~+40V.
    XTR103 outputs two 0.8mA current sources. The current sources are driven by VT2 and then added to the RTD to avoid
attenuation caused by the line and suppress line interference. The function of Rh is similar to that of R in XTR101. The function is exactly the same: limiting
the maximum value of the output current. Rini is a linear adjustment resistor, which can change the resistance value to change the linearity. The output signal
gets a current of 4~20mA after being connected to the external transistor VT1. RCV420 is a 4-20mA current-to-voltage dedicated converter (
will be introduced in "3" of this section), which outputs a 0~5V voltage after conversion.