eem2am
Banned
Hi,
The following is an op-amp circuit which reads a potential divider voltage where the upper divider resistance is an NTC thermistor.
http://i54.tinypic.com/2wpqdmf.jpg
LMC6035 OPAMP datasheet
**broken link removed**
-the thermistor connects between VCC and PL5
-The output of the op-amp is read by a microcontroller ADC.
-The Vcc = 5V
The temperature measurement is required to be very accurate when it is near zero degrees centigrade.
(this is because it measures water temperature in a shower pipe, and the shower must not be turned on if the pipe water temperature is zero degrees C. -This is because if it was, then the cold pipe may be frozen , and un-mixed hot water would go over the showerer and scald them)
The thing is, when the NTC is at zero degrees C, its value is 36000 Ohms.
This value of resistance gives a very low output voltage reading from the op-amp U4-A.
I am wondering how accurate the op-amp U4-A's output is when it is near ground?
The following is an op-amp circuit which reads a potential divider voltage where the upper divider resistance is an NTC thermistor.
http://i54.tinypic.com/2wpqdmf.jpg
LMC6035 OPAMP datasheet
**broken link removed**
-the thermistor connects between VCC and PL5
-The output of the op-amp is read by a microcontroller ADC.
-The Vcc = 5V
The temperature measurement is required to be very accurate when it is near zero degrees centigrade.
(this is because it measures water temperature in a shower pipe, and the shower must not be turned on if the pipe water temperature is zero degrees C. -This is because if it was, then the cold pipe may be frozen , and un-mixed hot water would go over the showerer and scald them)
The thing is, when the NTC is at zero degrees C, its value is 36000 Ohms.
This value of resistance gives a very low output voltage reading from the op-amp U4-A.
I am wondering how accurate the op-amp U4-A's output is when it is near ground?