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LOGO! - Projects: Heat level switching

Hey,
Logo8 programmed as a thermostat:
start 28 ° C stop 26 ° C
however, it starts at 28.5 ° C and stops at 26.3 ° C.
How come?
And is it not possible to give a start at 26.5 ° instead of just round numbers?
With thanks
Greetings Fernando

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Answers(1)

LOGO! 8 Thermostat Inaccuracy & Decimal Values

Dear Fernando,

The slight deviation you're observing (starting at 28.5°C instead of 28°C, stopping at 26.3°C instead of 26°C) is due to the inherent analog-to-digital conversion and resolution of the temperature sensor and the LOGO! 8's processing.

The LOGO! 8 doesn't work with infinitely precise temperature readings. It samples the analog signal and converts it to a digital value. This introduces a small amount of error. Also, the display resolution might show one decimal place while the internal comparison uses a different precision.

Regarding using decimal start values like 26.5°C: Yes, it is possible. You can directly input decimal values in the LOGO!Soft Comfort program for your temperature setpoints. There are no restrictions to only using whole numbers.

For more detailed information on LOGO! 8 analog input handling, please refer to the SiePortal documentation:

Sincerely,
Siemens Self Support

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