My current boards I have deployed in my garden use the DS18B20 to measure soil temperature. The DS18B20 requires a pull-up resistor on the signal wire (Dallas 1 Wire), and I am using a 4.7K resistor. I am going to try out a different soil temperature sensor - SMT50 - which does not require a pull-up resistor. It only requires an Analog input.
Will the 4.7K pull-up have an impact on the sensor readings? Do I need to perform a calculation on the input with the added resistance? I am trying to avoid a hardware spin if I can help it. Thanks!
czu001:
I am going to try out a different soil temperature sensor which does not require a pull-up resistor. It only requires an Analog input.
Will the 4.7K pull-up have an impact on the sensor readings? Do I need to perform a calculation on the input with the added resistance? I am trying to avoid a hardware spin if I can help it. Thanks!
The new sensor you are going to use, I'll call it the X1Jz_Mystery_922-X-SuperDoubleSeceretSensor. What is it really?
Apologies all.. the new sensor is the SMT50. I updated the original post.
Can't you just unsolder the resistor?
Yes, but I have several of them deployed in the field. I was hoping to just swap out the sensors and perform a firmware update, but if I must desolder then I'll do it.
In general, a pullup resistor will distort or confuse ADC readings, and without knowledge of the internals of the sensor, it may be impossible to correct.