DS18B20 Multiplier and Offset

Hi all - I’m pretty new to this so I apologize if this is common knowledge. I have a DS18B20 temperature sensor and a Campbell CR1000x. I am reading the sensor using VoltSE (https://help.campbellsci.com/crbasic/cr1000x/#Instructions/voltse.htm#kanchor110) in the CrBasic, which calls for a multiplier and offset to adjust the values (Calculating Multipliers and Offsets). I was wondering if these sensors had common multipliers and offsets, or if this is something I can determine on my own using a reference temperature and some controlled temperatures?

Hi @gdieter , Sadly the DS18B20 is not an Analog output like the Cr1000x “VoltSE” function is looking for… The DS18B20 communicates over 1-Wire interface

The DS18B20 will convert it’s measured Reading to a Digital Encoding and transmit that over the 1-Wire interface… Looking at the CR1000x, i don’t see a 1-wire module…

I wonder does Campbell have an external convertor module to convert the 1-Wire interface to something it can understand???

Edit, not looking good on their forum: Search Results:

Regards,

Hi @RobertCNelson, thanks so much for the speedy reply. So this is the actual sensor I am using (https://www.amazon.com/HiLetgo-DS18B20-Temperature-Stainless-Waterproof/dp/B00M1PM55K/ref=sr_1_3?dchild=1&keywords=DS18B20&qid=1634065847&sr=8-3). Admittedly I don’t know if it is a Digi-Key sensor or not…the folks at Campbell sent me this wiring chart (below) and information to get me started with the CR1000x, and then directed me here for determining mult. and offset. Does this DS18B20 operate over the same 1-Wire interface? I currently have the sensor connected and reading values using the 1H and circled ground port, and the values are showing up in the Campbell software (3rd image). I have applied some preliminary multipliers and offsets from some test values just to see how close I am and it’s about a degree off…not sure if the units of the bottom reading are actually volts though, maybe millivolts?

That is a classic DS18B20, it’s a really nice sensor, a lot of 3rd party manufactures do the over molding and the extended WaterProof wiring…

This sensor is: DS18B20 Programmable Resolution 1-Wire Digital Thermometer | Maxim Integrated

Is sadly only Digital, the ‘Analog’ values you are seeing are pure noise from the 1-wire communications bus…

Regards,

1 Like

Cheers, I’ll reach out to Campbell and see what they have to say! :slightly_smiling_face:

I reached out to Campbell with this info and they mentioned the C1 port can read an SDI12 sensor…do you know if the DS18B20 is an SDI12 sensor?

Hi @gdieter Nope, the DS18B20 is NOT an SDI12 sensor. The DS18B20 is a 1-Wire based interface.

Looking at the SDI12 spec, it shares more in-common with RS-232, but operating on a single wire.

While 1-Wire, is more in concept to I2C…

Why did you choose the DS18B20 for your application? Based on the capabilities of the CR1000x, i would instead look a pure Analog based Temp Sensor.

Regards,

1 Like

Fair question, forgot to mention this up top…we just had a couple of these lying around that a previous researcher was looking into using with an Arduino but I don’t think they got it working that way before they needed to deploy a sensor. I was just looking into the compatibility of the CR1000x and the DS18B20 to see if we needed to purchase new sensors or could make something work with what we already had.

If you still have the Arduino, you could use that to convert that sensor’s data from OneWire to…

https://www.pjrc.com/teensy/td_libs_OneWire.html

Thinking, either RS-232, SPI or I2C… It’s really up to you…

Regards,