2-142.5 Thermister Input (Only for TM type)2.5.1 Overview of Thermister InputThe control units of which part and product numbers end in “TM” is quipped with the leader lines whichenable the thermister input instead of the analog potentiometer. The change in the termister’s resistancevalues can be loaded as analog values by connecting the thermister with these leader lines.Mechanism for loading thermister input• Loads the change in the resistance values of the thermister connected externally as the change involtage, and then loads it as digital values by the AD converter in which a microcomputer is built.• The values converted to digital values are reflected in the special data registers (DT90040 orDT90041) and can be read in the user’s program.Non-isolated between the FPΣ thermister input unitand the power supply connector (24V).The red leader line is connected with the 3.3V powersupply and the black is connected with the Vin.Total precisionTotal precision= (Total precision of AD converter in which microcomputer is built: ±5LSBNote))+(Precision of thermister)Note) ±5LSB means there is a margin of error of ±5LSB for the values (0 to 1000) converted with ADconverter.Thermister resistance values and digital conversion values• Use the following formula for conversion of thermister resistance values and digital conversion values.• Digital conversion values changes within a range of K0 to K1000.1024 X 2.2Thermister resistance value (kΩ) = -2.2(Digital value+12)
