Comimark1Pcs SHT20 Temperature Humidity Sensor Modbus RS485 High Precision Transmitter

Its very unfortunate, despite of feed back for more technical info of product, no one has contacted to me, i was looking for Product Data sheet / power and signal cable details / register details ( if its available )

There is absolutely NO DOCUMENTATION with this part. Fortunately, I found a similar device on Amazon that did have the wire colors decoded: RED=+5V; BLK=COMMON; YEL=RS485 A+; WHT=RS485 B-.It comes defaulted to Address 1; baud rate 9600. To find the registers you need to actually communicate with it, search the internet for "SHT20 MODBUS commands". I found a device on banggood.com that must use the same chipset, and have the same registers.So, I eventually figured out how to use it, and now am reading Temperature (in tenths of degrees C) and relative humidity (in tenths of a %) So a reading of 276, 432 is 27.6 deg C at 43.2% RH.Seller, you need to add some form of documentation for this!

They work. sort of. Of the four units bought two don't read humidity anymore, and one returns garbage for temperature and humidity.They seem to produce significant heat internally. Powered with 24V and in still air the temperature reading will rise 4-8 degree Celsius within a few minutes. This is consistent to all the units. and only the initial readings are about right to the ambient temperature. If you have a switched fan the readings are useless as you can't calibrate that out. Who knows, maybe you are supposed to leave them unpowered unless you are actively taking a reading every few minutes... Not sure how accurate humidity is, but two units next to each other are reading +/- 10% RH.Two gotchas for usage:The unit must be powered cycled for address configurations to take effect.You must wait after writing a configuration register before reading another register. otherwise the read will fail. EG write modbus address register, wait 500ms, read modbus address register.

Seems like a good sensor. I used with a PLC but was not able to let modbus master control the scan. Experimented with many timing parameters but ended up manually triggering the scan which seem to work 100%.

The comment from a prior customer allowed me to hook it up and get it running immediately.