Lufft SHM31 User Manual

Communication in SDI-12 mode
Snow depth sensor SHM 31, V2.1 49
HSN
Snow height
DSTC
Calibrated distance
OSF
Snow flag
OFF
Fog flag
OSN
Normalised signal strength
ER
SHM31 error
DSTA
Device status
STA1
Sensor status 1
STA2
Sensor status 2
DRT
System time at request
E
xample:
0IM_002!
0,HSN,mm,cur<CR><LF>
10.11. Switching commands
Switching commands are implemented as manufacturer-defined SDI-12 ‘extended’ telegrams and
are used to trigger procedures.
Switching commands are composed of the prefix X defined in the SDI-12 standard and a three-
digit individual code. The code corresponds in most cases to the corresponding code of the ASCII2
protocol.
If the command was successfully received, the telegram is answered with ‘OK’ added to the
command code.
If the command cannot be executed, e.g. because other procedures are still ongoing, the telegram
is answered with ‘busy’ added to the command code.
If the three-character command code is unknown,
aX_noCmd<CR><LF>
will be the response.
10.11.1. Unit system changeover command
The command is used to change the system of units used to display the SDI-12 data between
metric and US units. The command is implemented as an X command.
The parameter change is applied immediately and stored in the sensor’s configuration memory.
Command: aXUN<U/M>!
Response: aXUN<U/M><CR><LF>
U: US units
M: Metric units
Example: change to metric units
0XUNM!
0XUNMok<CR><LF>
10.11.2. Device reset command
The command initiates a device reset.
Command: aXRES!
Response: aXRESok<CR><LF>
This is followed by a reset, i.e. the device cannot be reached for a few seconds

Lufft SHM31 Specifications

General

Housing material	Plastic
Humidity Range	0% to 100% RH
Humidity Accuracy	±2% RH
Mounting	Wall
Measurement Parameters	Temperature, Humidity
Output	RS-485
Power Supply	12 VDC to 24 VDC

Summary

Read Before Commissioning

Safety Instructions

Provides essential safety precautions for assembly, operation, and handling of the sensor.

Laser Safety and Classification

Details laser safety Class 2 compliance and exposure guidelines to prevent eye damage.

Item and Technical Data

Technical Data

Presents detailed specifications including measuring parameters, interfaces, operating conditions, and dimensions.

Device Description and Operation

Measurement Method Principles

Explains the phase measurement method utilizing laser pulses for distance measurement.

Assembly and Commissioning Introduction

Guides on sensor mounting, alignment, and initial setup procedures including zero measurement.

Sensor Assembly

Assembly Procedures

Details the physical mounting of the sensor on a mast using provided clamps and alignment procedures.

Device Connections

Connector Pin Assignment

Maps the interface cable cores to specific pins on the SHM 31 connector.

Data Interfaces

Lists the available communication interfaces: RS485, SDI-12, and RS232.

Commissioning the Sensor

Important Commissioning Information

Highlights key points for successful commissioning, including software usage and laser safety.

UMB ConfigTool.NET Setup

Introduces the UMB ConfigTool.NET software for sensor configuration, firmware updates, and data acquisition.

UMB-ASCII 2.0 Communication

Communication Syntax

Defines the grammatical structure and components of UMB-ASCII 2.0 data telegrams.

UMB Communication Protocols

Measuring Channels Overview

Lists the available UMB channels with their measured variables and units.

Binary Protocol Communication

Explains how to communicate using the UMB binary protocol, including data frames and addressing.

UMB Binary Protocol Status and Error Codes

Lists and explains status and error codes encountered in UMB binary protocol communication.

SDI-12 Mode Communication

SDI-12 Settings and Configuration

Guides on configuring the sensor for SDI-12 communication via ConfigTool.NET or ASCII commands.

Query Measured Value Parameters

Describes the command for querying measured value parameters and their codes.

Switching Commands

Introduces manufacturer-defined SDI-12 commands used to trigger specific procedures.

Calibrate Offset and Angle

Describes the command to start a process for determining and setting distance and angle offsets.

Parameter Setting Commands

Introduces commands for reading and setting sensor parameters in SDI-12 mode.

Modbus Mode Communication

Modbus Functions Overview

Lists the implemented Modbus functions applicable to the SHM 31-UMB.

Read Input Registers Function (0x04)

Details the function for reading measured values and status information via input registers.

Signal Quality Check

Application of Target Plates

Explains how to use target plates to check the sensor's signal intensity and reflectivity response.

Service, Maintenance, and Support

Firmware Update Procedure

Guides on how to update the sensor's firmware using the UMB ConfigTool.NET software.

Troubleshooting Sensor Faults

Lists common errors, their possible causes, remedies, and specific error codes.

Technical Support and Repair

Offers contact information for obtaining technical assistance and repair for the sensor.