The RS-WS-N01-8 DIN rail temperature and humidity sensor

The RS-WS-N01-8 is a very basic but well working temperature and humidity sensor that can be mounted on a DIN rail and is attached to an RS485 ModBus network. It’s a relatively cheap device (at the time of writing around 5 Eur). This blog article is just a quick summary of the default configuration and registers since there is some rumor one needs to violate the ModBus protocol to configure this sensor - this is not required.

Default configuration

The default configuration is a baud rate of 4800 bps and a device address of 1. These settings can be changed by using the holding registers 0x7D0 and 0x7D1 via standard ModBus commands.

BAUD Rate	4800
Device address	1

Known registers

The following registers are known on the device (I’ve enumerated all registers using a quick tool - there are no other readable input or holding registers). All registers are accessed as holding registers!

Address	Content	Read/Write
0x0000	Humidity value (IEEE float, multiplied by 10)	Read
0x0001	Temperature value (IEEE float, multiplied by 10)	Read
0x07D0	Device address	Read/Write
0x07D1	BAUD rate (0: 2400, 1: 4800, 2: 9600)	Read/Write

As one can see the temperature and humidity are available as IEEE floats, all values are multiplied by 10 so one has to divide them by 10 to get real readings.

The device address can be set by writing to 0x7D0. This setting is effective immediately.

The baud rate can be set using the 0x7D1 register. This setting is effective immediately. I’ve seen the following values - this is not a complete list:

Setting in 0x7D1	BAUD rate
0	2400
1	4800 (default)
2	9600