RTD - PLC Programming & Automation

Wiring a Pt100 into an Analogue Input and Getting Degrees Out: Three-Wire Compensation and the Open-Circuit Reading

The Pt100 head with its three leads, the 22 m run, and the two terminal strips it lands on: IN-0/A, IN-0/B and RTN-0/C on the 1756-IR6I with the two-wire short drawn dashed, and M+, M-, I+ and I- on the SM 1231 RTD with the bridge the S7-1500 function manual describes

A Pt100 RTD input wired two-wire over 22 m of 0.5 mm² cable into channel 0 of a 1756-IR6I reads 104.1 °C in a bath that the reference thermometer says is 100.0 °C, and the same sensor with its third lead landed on RTN-0/C reads 100.0 °C. Lift lead A off the module and the … Read more

PLC Hardware Components and the Software That Uses Them

by PLC

Timing chart showing a field input rising, the input image bit following at the next input scan, the coil in logic changing during the program scan, and the physical output finally switching after the output scan, about one scan behind the field

What is in a PLC rack and how the software sees it: power supply budget, CPU memory, I/O cards, tasks and routines, and tags against S7 addresses.

PLC PID Control: Set Up and Tune a Loop in Studio 5000

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Timing chart of a loop startup: setpoint step, control output saturated at 100 percent, deviation alarm active, then the process variable settling inside a 1 degC band

Scale the analog signals, pick PID or PIDE, put the loop in a periodic task, then tune from a bump test. Siemens PID_Compact covered as well.