LM34: Understanding output voltage

Alex Rodriguez

Part Number: LM34

I am connecting LM34CZ/NOPB to a PLC analog input 0-10 V. LM34 is powered by 24 VDC and I get .560V at about 78 degrees Fahrenheit on the output signal of LM34 but how do I interpret that signal? My PLC Engineering units is set to receive 0 for min and 1000 for max and it is receiving 56 in data but that isn’t 56 degrees temperature. Question is what is the min/max of the sensor? And how do I interpret that signal in reference to degrees?

over 5 years ago

0 Audrey Dearien7 over 5 years ago

TI__Expert 4875 points

Hi Alex,

You are correct that 560 mV corresponds to 56 F. The temperature range of the LM34C is -50 to 230 F. The device is calibrated to degrees Fahrenheit, with a linear scale of 10 mV/F. This means the output ranges from -500 mV to 2300 mV. At 78 F, the output should be 780 mV.

Can you share your schematic so that I can further address this issue?

Thanks,

Audrey

0 Alex Rodriguez over 5 years ago in reply to Audrey Dearien7

Prodigy 20 points

I don't have a schematic but I am connecting 24 VDC to +Vs, Vout to PLC analog input and GND to ground or (-)24 VDC. Hope this helps

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LM34: Understanding output voltage