LM35 Sensitivity
Posted: Thu Jul 21, 2016 8:04 am
Hi guys,
Now I have, with the help of Dazz, sorted out the minus temperature readings on my fridge controller using the LM35 sensor connected as per Fig 18 of the datasheet. When I use the LM35DZ sensor in positive temperature applications, the output from the sensor via the PIC to the LCD is very stable, the numbers of degrees change very positively up or down.
What I find now with using the LM35C in the minus range, with the sensor now having two outputs instead of one, is that the display is very jittery. When the number of degrees changes, the readings would sometimes jump and down over 3 numbers ie if the reading is for example -15......then the display will "oscillate" between -14 and -16.
This jittery output is a problem as it triggers the cutoff temperature when the actual temperature has not really been reached by the fridge.
Is this jittery output as a result of the "negative" output being above ground? I have tried unsuccessfully to try and stabilize the output using small caps and resistors on the sensors. Can one stabilize these outputs in software???
Would appreciate it if somebody in the know can assist me with the above.
Thank you
Regards
Ted
Now I have, with the help of Dazz, sorted out the minus temperature readings on my fridge controller using the LM35 sensor connected as per Fig 18 of the datasheet. When I use the LM35DZ sensor in positive temperature applications, the output from the sensor via the PIC to the LCD is very stable, the numbers of degrees change very positively up or down.
What I find now with using the LM35C in the minus range, with the sensor now having two outputs instead of one, is that the display is very jittery. When the number of degrees changes, the readings would sometimes jump and down over 3 numbers ie if the reading is for example -15......then the display will "oscillate" between -14 and -16.
This jittery output is a problem as it triggers the cutoff temperature when the actual temperature has not really been reached by the fridge.
Is this jittery output as a result of the "negative" output being above ground? I have tried unsuccessfully to try and stabilize the output using small caps and resistors on the sensors. Can one stabilize these outputs in software???
Would appreciate it if somebody in the know can assist me with the above.
Thank you
Regards
Ted