Measuring Circuit. shows a simplified schematic for the ER180 recorder with manual range selector unit-6 thermocouple inputs and 2 ranges. In the standard ER-180 recorder with thermcoouple input, a slidewire resistor with non-linear resistance perunit length is used to correct for the non-linearity ( 记录笔、记录纸 ) of thermocouple input. However, in the recorder with manual range selector unit, linearizer circuits are used for respective ranges to correct for the thermocouple's non-linearity (the slidewire resistor is linear). The linearizer's input-output characteristic is made to agree with the thermocouple. The linearizer converts the thermocouple. Figure 4-2 shows a simplified schematic for the ER-180 recorder with manual range selector unit RTDs input, 6 measuring points and 2 ranges. As RTDs have comparatvely low resistances, relay contacts are used in the range selector circuit to minimize the circuit resistance.