ADU-500 is an ultra low power, wireless RTU with data logging and alarming capabilities. The battery powered RTU incorporates three digital inputs, two analog inputs, one pulse counter input and multiple excitation options for powering measuring transducers. The device supports acquisition of up to 48 measurement channels, based on the popular SDI-12 communication protocol. ADU-500 uses an internal cell modem to automatically send data and alerts. The RTU is available for GSM/EGPRS and CDMA2000 network environments. A D-size Lithium Thionyl battery can provide autonomous operation for over 10 years.

The Infinite advantage

The ADU-500 RTU Version 4.x incorporates the common flexible form factor (HL, CF3™) Modem modules of Sierra Wireless. OEM versions of ADU-500 can now virtually support any LPWA, 4G, 3G, 2G mobile network technology. The 3G Version of the RTU (ADU-500-3G) includes GNSS capability (GPS & Glonass Sirf V).

Measurements & Data Logging

The digital inputs are scanned by the system controller for detecting an alarm condition. Analog input gain, scaling and alarm limits are user definable. The analog inputs and SDI-12 sensors are sampled according to the user defined sampling rate. Sampling rate and sampling duration affect the battery life according to the transducer power supply requirements.

SDI-12 Serial Bus

SDI-12 is an asynchronous, ASCII, serial communications protocol that was developed for intelligent sensory instruments that typically monitor environmental data. The communication is achieved by digital communications. The addressing system allows data recorder to communicate with several microprocessor-based sensors over a single line. ADU-500 is compliant to the SDI-12 Standard Version 1.2 and supports extended commands for sensor configuration, in terminal mode. ADU-500 can collect data from several SDI-12 sensors for a total amount of 48 measurement channels. Learn more »


ADU-500 supports acquisition from sensors with RS-485 interface, using the popular MODBUS ASCII protocol. Up to 10 measurement channels from several sensors are supported.

Transducer excitation

The unit provides multiple excitation options for measuring transducers.

Alerting & messaging

SMS announcements include alert messages and periodical Status messages for verifying unit availability. The unit supports discrete alerting for several users. Message texts are user definable.

Data Transmission

ADU-500 supports periodical data transmission according to user defined parameters. The unit can send data via SMS to predefined users or to an internet server via FTP.

Setup and Remote Configuration

The unit can be programmed locally through the serial port or remotely via SMS by using simple ASCII configuration commands. The command set features commands for configuring input alarm parameters, scaling parameters and alarm limits, timing parameters and defining user groups. ADU-500 can be remotely reconfigured by sending configuration commands to the unit during the periodical status message processing.

Ordering Codes

Code Description
ADU-500-2G Autonomous RTU/Datalogger with 2G GSM MODEM
ADU-500-3G Autonomous RTU/Datalogger for 3G GSM MODEM


Power supply
Supply voltage Internal: 3.6V, 13Ah Lithium Thionyl battery (Saft LSH-20 recommended)
External: 9..24 VDC, 26VDC max
Stand by 18μA 3.6V
Communication SMS: average 50mA, 2A peak, FTP: average 240mA, 2A peak (GPRS/EGPRS), 650mA (WCDMA)
Measurement Up to 750mA at 3.6V (according to sensor supply requirements)
Processing unit
System controller Ultra low power ARM 7 MCU
Communication processor ARM 9 MCU
Data memory 128 KByte EEPROM
Digital inputs
Digital inputs 3, dry contact, 0-30VDC
Pulse counters 1, 2KHz, common with DI 3
Analog inputs
Input 1 (AI1) 2, Range: 0-5V/0-2.5V, 0-1V, 0-100mV, 12 bit resolution, Gain: 1-200, digitally set (PGA).
Input 2 (AI2) 2, Range: 0-2.5V, 0-1V, 0-100mV, 0-10mV, 0-20/4-20mA, 12 bit resolution, Gain: 1-200, digitally set (PGA).
Serial Bus features & options
SDI-12 48 channels, Support of extended commands in Terminal mode
RS-485, MODBUS 10 channels, MODBUS ASCII protocol
I2C Low power I2C sensors (OEM versions only)
RS-485 Sensors with RS-485 interface and proprietary protocol (OEM versions only)
Sensor excitation
Output 1 9VDC/250mA or 12VDC/200mA (Jumper selection)
Output 2 5VDC/200mA
Output 3 3.3V/250mA
Status & Alarm SMS
Data FTP or SMS
Wireless modem Quad Band 2G (Sierra Wireless HL6528) or Quad Band 3G (Sierra Wireless HL8548-G)
Antenna connector GSM: SMA Jack
Serial interface USB, up to 115 kBit/s
Location solution
GNSS GPS & Glonass Sirf V (HL8548-G only)
Antenna connector SMA Jack
Temperature -40°...65°C, operating
Indications 2 LED, Network status, Operation status
Dimensions 130 x 130 x 75 mm
Protection IP66
Weight 0.5 kg (without battery)
Product Brochures
Document File
ADU-500, Autonomer RTU/Datenlogger, Broschüre V:2.2 ADU-500 German.pdf
WAT, Cloud Server Brochure V:1.1 WaT Datasheet.pdf
ADU-500 V:4.x, Autonomous RTU/Data Logger Brochure V:4.0 ADU-500_4x English.pdf
Technical Documents
Document File
LSH-20, D-size, Lithium-thionyl battery LSH20.pdf
WA Manager User Guide V:6.0 WA Manager V6.0.pdf
Application Documents
Document File
In situ measurement of soil moisture In situ measurement of soil moisture.pdf
Autonomous Intrusion Alarming via SMS Autonomous Intrusion Alarming.pdf