Reply To: Please Help! Meter CTD Gen2 being blocked by Yosemitech 511-a

We’ve been using Y-511a sensors together with Gen 2 Hydros21 CTD sensors and have had no problems with communication, however we’re using our own modbus adapter (based on a MAX13412 chip) instead of the Neil’s modbus wing.  As Sara said, the sensors shouldn’t be talking the the Mayfly at the same time since the Y-511 has a 40-second warmup time, followed by a 8-second sampling time, so the Mayfly doesn’t hear anything from the Y-511a for almost a minute after it is powered up.  I’m not sure if the modbus wing you’re using has a level-shifter on the SDI-12 data line, but we found that most level-shifting circuits cause inconsistent communication with the Meter Group sensors, probably because the logic high level of their sensors is only 3.6v, which in our experience is safe enough to connect directly to the Mayfly’s digital input.