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Need help scaling 4-20mA signal in Fatek PLC

wicked14

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Jun 27, 2025
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Im using an Autonics THD-R-C temperature and humidity sensor that outputs a 4-20mA signal, connected to a Fatek PLC analog input (1-bit, range 0-16380). This is actually my first time working with 4-20mA instead of 0-10V, and i need help with scaling the input so I can get accurate temperature readings. The sensor outputs 4mA at -19.9degrees C and 20mA at 60degrees C.., how do I convert the raw PLC value into the correct temperature?
 
Use this formula: Temp = ((Raw - 3276) × 79.9 ÷ 13104) - 19.9. it scales the 4–20 mA input (3276–16380) to your sensor's -19.9 °C to 60 °C range
 
Use this formula: Temp = ((Raw - 3276) × 79.9 ÷ 13104) - 19.9. it scales the 4–20 mA input (3276–16380) to your sensor's -19.9 °C to 60 °C range
Here, 3276 is the raw value at 4mA (calculated as 16380 × (4/20)) correct?
 
Here, 3276 is the raw value at 4mA (calculated as 16380 × (4/20)) correct?
Not quite, your input card doesn't start from zero at 4 mA, it treats 0 mA as raw 0. That's why you got ~4095 for 4 mA instead of 3276. You should stick with 4095–16380 as your usable range for scaling
 
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