Nice to see the pic of the 3G logger.
I was wondering if you got the link to the LT400 working.
I’ve been attempting to access the LT500 but not had any success decoding the LT500 protocol that runs on top of the modbus/RS485.
I have had packets as per the “Insitu Modbus_Communication_Protocol_5.10.pdf” but seems there is some initialization sequence that is needed before reading the sensors. I wonder how far you got with it.
I have got Keller Nano Level device that is very accurate in low water (capactive sensors) and water temperature change polling.
My hardware arrangement is prototype with a RS485 plugin using an Olimex STM32-H407 running off a 12V source. Pic enclosed. This is of the sensor in stable jar of water so the water depth isn’t varying except for evaporation. The sensor depth reading variation is from temperature variation.
BTW – I would think that with the mayfly interfacing to an RS485 chip (sparkfun has them) – the 12V would be well isolated. But as Shannon said, the 12V will fry 3V mayfly logic should they ever meet.
One of the issues with any electronics is they often take a surge on power up. For 12V sensors this may be a problem with a boost circuit, switched the way it is on the Mayfly. Powering is always tradeoffs and it may take some characterization. https://github.com/EnviroDIY/EnviroDIY_Mayfly_Logger/issues/1