Siemens SIMATIC S7-1200 System Manual page 1521

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For optimum operation of the cold junction compensation, the thermocouple module must be

located in a thermally stable environment. Slow variation (less than 0.1 °C/minute) in

ambient module temperature is correctly compensated within the module specifications. Air

movement across the module will also cause cold junction compensation errors.

If better cold junction error compensation is needed, an external iso-thermal terminal block

may be used. The thermocouple module provides for use of a 0 °C referenced or 50 °C

referenced terminal block.

Selection table for the SB 1231 thermocouple

The ranges and accuracy for the different thermocouple types supported by the SB 1231

Thermocouple signal board are shown in the table below.

Table A- 225 SB 1231 Thermocouple selection table

Thermocouple

Thermocouple values below the under-range minimum value are reported as -32768.

Thermocouple values above the over-range minimum value are reported as 32767.

Internal cold junction error is ±1.5 °C for all ranges. This adds to the error in this table. The signal board requires at least

30 minutes of warm-up time to meet this specification.

Table A- 226 Filter selection table for the SB 1231 Thermocouple

Rejection frequency (Hz)

To maintain module resolution and accuracy when 400 Hz rejection is selected, the integration time is 10 ms. This

selection also rejects 100 Hz and 200 Hz noise.

S7-1200 Programmable controller

System Manual, V4.2, 09/2016, A5E02486680-AK

Nominal range

range low limit

Integration time (ms)

A.14 Analog signal boards (SBs)

Normal range

accuracy @ 25 °C

Signal board update time (seconds)

Technical specifications

Normal range

-20 °C to 60 °C