ComWinTop CWT-THxxS Series - temperature and humidity sensor

What it is

The ComWinTop CWT-TH03S-H is a small RS485 sensor that reports air temperature and relative humidity from wherever you mount its probe, rated -40 to +120 °C and 0 to 100 %RH. It has no power path and nothing to switch, so myPower24 only reads it and logs it, through the LoggerV. It also has no display and no buttons: its Modbus address and its baud rate are registers, changed from its device page over the same bus the sensor answers on, so it has to be reachable on its current settings before either can be changed. ComWinTop sells a wider CWT-THxxS series, but CWT-TH03S-H is the only model myPower24 offers, and nothing on the bus says which model is fitted, so the label on the probe is the only record of what a given unit is rated for.

How it connects

RS485, Modbus RTU. The rate is whatever the LoggerV port is set to, because the driver fixes none. The sensor leaves the factory at 4800 and accepts 1200, 2400, 4800, 9600, 19200, 38400, 57600 and 115200. You give it a Modbus address and the LoggerV probes the line for it.
Ethernet, Modbus TCP. Reachable only through a Modbus TCP to RTU gateway, the same as any other RS485 device. It is not used on Solar MD sites and has not been tested with this sensor.

The sensor leaves the factory at 4800-8-N-1.

The factory Modbus address, and the maximum RS485 bus length quoted for this series, are both in the ComWinTop CWT-THxxS series manual. Check it before planning a long run, or before wiring a second sensor onto a line that already has one.

What plant control can do with it

Nothing. The sensor is monitoring only. It has no power path, and the LoggerV never sends it a setpoint, a mode or a command, so it cannot be added to plant control.

What the platform records

Temperature, °C.
Humidity, %RH.

Both are read every 5 seconds and shown to one decimal place, accurate to ±0.5 °C and ±5 %RH. The platform keeps the highest and the lowest reading in each logging interval as well as the average, so a short hot spot or a condensation spike is not smoothed away. Neither reading is restricted: anyone who can open the device can see both. Chart them against anything else on the plant with Device Historical Analytics.

Wiring

Connection diagrams are generated by the platform's Add-Device wizard; see How to add a device in myPower24. The Solar MD connection guide for these sensors is reproduced here.

Solar MD connection guide SMD_SMD_LV2/TEMP_HUMID_MS_00, LV221 Temp Humid Sensors

The sensor end is a four-wire flying lead and two colour sets are in circulation, so check the leads on the unit in front of you before terminating. On units supplied with the LoggerV, which is what the drawing shows, blue is RS485 B, purple is RS485 A, orange is the positive supply and black is the supply negative. On units sourced elsewhere, per the vendor manual, blue is RS485 B, yellow or green is RS485 A, brown is the positive supply and black is the supply negative. Both sets agree on blue and black, and differ on the two that matter.
The sensor is rated DC5 V to DC30 V, so the logger's 24 VDC auxiliary rail suits it with headroom, and Solar MD runs them at 27 V on the bench. The vendor manual's feature list quotes DC5V to DC24V and contradicts its own wiring table; the wider figure is the correct one.
The logger end is an RJ45 into the LoggerV's RS485-1 port. Crimp it to the T568B pinout of the ANSI/TIA-568-E standard. Pin 4 carries RS485 B+ and pin 5 carries RS485 A-, which is the pair the sensor's blue and purple leads land on.
Terminate the bus with a 120 Ohm RJ45 termination resistor. The drawing shows it plugged into the logger's second RS485-1 socket, so the two sockets are the two ends of one bus.
The same drawing also covers the DONGKER XY-MD02, a different sensor that this page does not document.

Setting it up

Connect the sensor per the generated diagram: the RS485 pair, the 24 VDC supply and ground, and the terminator at the logger end. Check the wire colours against the two sets above.
Add the device on the LoggerV; see How to add a device in myPower24. Set the LoggerV RS485 port to the rate the sensor is currently on before you scan, or nothing answers; a sensor out of the box is at 4800. The wizard asks for a Serial Number, and this sensor publishes none, so type the number off the unit label or your own asset number, up to 50 characters. It becomes the device's permanent identity on the platform.
If more than one sensor shares the RS485 line, give each its own address: open the device page, Settings, Communication Settings, and set Slave ID to a value from 1 to 254. The sensor moves to the new address immediately and the LoggerV follows it, so there is nothing to re-add.
Leave Baudrate alone unless you have a reason to change it, and read the warning below first.
You know it worked when Temperature and Humidity on the Actual Values tab track the conditions at the probe. Both sitting on exactly 0.0 is the start-up value, not a reading.

Changing Baudrate re-rates this sensor only. Baud rate belongs to the shared LoggerV port and to every device on that line, so the moment you change it the sensor drops off the bus until the port, and every other device on the line, are changed to match. There is no per-device override to recover from.

On the device page

Two tabs, and no Info tab: the sensor carries no nameplate or firmware registers to fill one.

Actual Values has two cards. Measurements shows Temperature in °C and Humidity in %RH, each to one decimal place. Communication shows Slave ID and Baudrate as read-only values, so the bus settings can be checked without opening Settings.
Settings has one section, Communication Settings, holding Slave ID and Baudrate. Those two are the only settings the sensor has.

A healthy link reads: both measurements moving with the conditions at the probe, Baudrate showing a rate label such as 4800bps rather than a bare number, and Slave ID matching the address you gave the sensor.

Troubleshooting

"Failed to scan ID (device did not respond to all register groups)": the sensor did not answer, so it was not added. Check the RS485 A and B polarity first, since blue and purple are easy to swap, then that the LoggerV port rate matches the sensor, then the address. The same message appears when a different device answers on that address.
"Serial Number required. Please provide serial number": Try to connect was pressed with the Serial Number field empty. The field is mandatory and the scan does not start without it.

A sensor that was working and goes quiet is usually the bus rather than the sensor: a missing terminator, a second device on the same Slave ID, or a baud rate changed on one device and not on the others.

Who can do what

Regular user (basic): sees the device page and both readings, and can edit both settings, Slave ID and Baudrate.
Advanced user (advanced): nothing further on this device.
OEM (oem): nothing further on this device.

A higher tier bypasses the lower gates, so there is nothing on this sensor that only an advanced user or an OEM can reach. Baudrate is not gated at all: anyone who can open the device page can change it, with the effect described above.

Tips and gotchas

Two sensors on one line need two addresses, set one at a time. Both ship on the same factory address, so wire and address the first before connecting the second, or they answer together and neither scans.
Nothing stops the same serial being entered twice, because the platform cannot read one off the sensor to check it against. Agree a convention, the unit label or a site asset number, before adding a batch.
Calibration cannot be done from the platform. The sensor holds a temperature offset and a humidity offset that are settable over the bus, and the device page exposes neither, so a unit reading consistently high or low has to be trimmed with a Modbus tool.
A sensor whose address nobody wrote down can still be found. It answers an address query sent to the RS485 broadcast address, so a Modbus tool can read the address back. This only works with that one sensor connected.