[colemanjj]

Thanks for asking,

After trying several simpler WiFi and cellular boards with only moderate success for about a year, I moved over to the Particle platform.  With generic ESP8266, adafruit feathers and FONO-feathers I found it hard to get things working dependably.  I found cellular communication particularly difficult. I still use some of the other platforms for WiFi but for cellular I find the Particle Electron to be well integrated into a web interface for programming and for monitoring the processor, has good documentation and has code and code examples that mostly work first time. It also has a simple interface for programming the processor over the air. That is particularly important to me because my units are mostly located in difficult to access locations. All those nice things having been said, they are a little expensive and the Electron seems to be only available as a “kit” that contains several things I don’t need.

john

[colemanjj]

neilh,
The TDS code currently posted by DFROBOT for the Gravity: Analog TDS Sensor/Meter for Arduino is a total re-write since I downloaded it. The code I downloaded about 6 months ago had an error in it (applied temperature correction to the raw analog voltage) The updated code is much more modular (a bunch of functions) and seems to have the TDS calculation correct now, with temperature correction applied after calculating electrical conductivity. I haven’t tried the new code but it seems to use the same multi-nomial equation to convert from voltage to electrical conductivity. I’m not sure where they got the coefficients for the equation but I developed my own equation from running the DFROBOT sensor side-by-side with a Onset HOBO U24 logger for about 3 months. I’m going to run my DFROBOT sensors side-by-side with Onset loggers for the foreseeable future because I’m not sure if there is variation in response between individual DFROBOT sensors.
BTW, the DFROBOT TDS sensor seems like it might be stable over long periods. I’ve been sampling the same one at 15 minute intervals since June and haven’t seen anything weird. I won’t know for sure about stability ’till I download the Onset logger in the spring to compare to the DFROBOT sensor data.

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