Lufft SHM31 User Manual

Communication in Modbus mode
54 Snow depth sensor SHM 31, V2.1
When writing to a parameter register, the new value is entered into the permanent memory, but is
only active after a device reset. In other words, the register only supplies the new value when read
after a reset. The value to be written is checked to ensure it is permissible. If the set limits are
exceeded, the sensor responds with an ‘Illegal Data Value’ Modbus exception and does not
execute the command.
The actions are executed when the value 0x3247 (hex) or 12871 (decimal) is written to the
corresponding register. If the action cannot be executed, the sensor responds with an ‘Illegal Data
Value’ Modbus exception.
Action registers always return 0 when read.
Action register
Reg.
Nr.
Reg.
Adr.
Function
Description
1
0
Sensor Reset
Initiated a sensor reset. During the reset process
Modbus communication is interrupted for a few
seconds
2
1
Measurement
Start
Starts normal measurement operation *)
3
2
Measurement End
Terminates normal measurement operation *)
4
3
Laser On
Laser permanently on (e.g. for sensor alignment) *)
5
4
Laser Off
Turn laser off after “Laser On” *)
6
5
Automatic
Calibration
Automatic Calibration of reference angle and height
*)
7
6
Automatic Height
Calibration
Automatic Calibration of reference height *)
8
7
Start defrosting
Start defrosting process
9
8
End defrosting
Terminate defrosting process
*
) Action can only be executed if the current operating state allows it. If not, the write process is
answered with the ‘ILLEGAL_DATA_VALUE’ Modbus exception. This is also the case if an action
to be started is already active.
P
arameter register
Reg.
Nr.
Reg.
Adr.
Function
Values
Factor
10
9
Operating mode
block heating
0 = OFF
1 = automatic
2 = start single defrost operation
3 = terminate defrost operation
1
11
10
Operating mode
window heating
0 = OFF
1 = automatic
2 = start single defrost operation
3 = terminate defrost operation
1
12
11
Enable external
heating control
0 = ignore ext. control pin
1 = enable ext. control pin
1
13
12
Automatic defrosting
after power on
0 = OFF
1 = ON
1
14
13
Reference height
Reference height above
measurement point in mm
Range: -16000 … +16000
1
15
14
Sensor tilt angle
Reference angle in °
Range -180 … +180
1
16
15
Use accelerometer
angle
Use current angle from
accelerometer for calculation
0 = use stored reference angle
1 = use current accelerometer angle
1
17
16
Acceptance time for
snow height change
Time to accept snow height change
exceeding the configured max. snow
height difference [sec]
Range: 0 … 65535
1

Lufft SHM31 Specifications

General

Brand	Lufft
Model	SHM31
Category	Accessories
Language	English