Remote Terminal Unit with Display

Pliant Technology Specialists

Pliant : readily yielding to influence

  • Host Interface Options:
    • MODBus RTU protocol: the “PRTU/RTU”
    • 4-20mA Output: the “PRTU/RTU/4-20”
    • Custom RS232 protocols available
  • Sensor Interface Options:
    • ECN protocol: the “PRTU/RTU/ECN”
    • Modem-based communications using
      • Leased-line modems: the “PRTU/RTU/MDMLL”
      • Dial-up modems: the “PRTU/RTU/MDM”
  • LED Display and operator switches
  • EEPROM for non-volatile storage of set-up parameters
  • Level-controlled relay output with user-programmable alarm conditions
  • Operates on 12VDC

Standard Features

The ///AMASSER PRTU is a host communications module which polls a remote ///AMASSER PSE shaft encoder and provides the retrieved data to a host device such as a SCADA, PLC, … The PRTU is designed specifically for polling the PSE. In cases where the PRTU is equipped with a built-in modem, it enables practically unlimited distances between your host machine and the remote sensor. The retrieved data is displayed on a LED digital display. Below are some example configurations that are possible between the PSE and your host machine:


The PRTU/RTU provides MODBUS registers that include the water level to 3 decimal places, the RTU address and the Alarm trigger points and hysteresis for the relay output. Distances of up to 4000' are supported between the PRTU/RTU and the host using two twisted pairs (full duplex).

Digital Display

The digital display and operator switches allow the user to view the realtime data as well as set the following parameters (if applicable): MODBUS address, Alarm UPPER, Alarm UPPER reset, Alarm LOWER, Alarm LOWER reset, 4mA OFFSET, 4-20mA SPAN, Cal 4mA, Cal 20mA.

Relay Output

All PRTU shipped after July 1, 2003 are equipped with a level-controlled relay output. The user defines the UPPER and LOWER levels for which the relay closes. These levels typically correspond to flood and drought conditions. The hysteresis for each of the trigger points is also user-configurable.

4-20mA Ouput

The “/4-20” option provides a 4-20mA signal proportional to the water level using by means of a 16-bit DAC. The water levels corresponding to an output of 4mA and 20mA are user-configurable from the digital display. Also, although the DAC is factory-calibrated, the unit features a calibration mode whereby 4mA and 20mA current levels are provided as a reference for fine adjustment of the device if necessary.

Modem-based Communications

The PRTU can be equipped with a leased-line or dial-up modem. This allows unlimited distances between the PSE sensor and the PRTU.

For leased-line modem order with option "/MDMLL".
For dial-up modem order with option "/MDM".


Processor : Atmel 89S8252 @ 3.6864 MHz.
Word Size : 8 bit data - 8 bit instruction
Memory : 89S8252, 256 bytes RAM
EEPROM 2 kbytes

Host Interface

/4-20 option: 4-20mA output

Sensor Interface

/MDMLL & /MDM: Built-in leased-line or dial-up modem.
PRTU/RTU/ECN: ECN protocol

Master/Slave set

Polls the PSE shaft encoder at fixed rate (1/sec for /MDMLL) and loads MODBUS registers with realtime data for retrieval by host device Provides data to host via MODBUS RTU. 4-20mA output available (option “/4-20”)


ASCII accumulated level of remote sensor

Power Supply

Configured for external 12 V lead-acid battery
9 V 565 mAHr alkaline battery backup
(Only if 9 pin connector is mounted)


9 pin and 8 pin AMP CPC Connectors
Current Carrying Capability - 1.5 Amp rating
Dielectric Withstanding Voltage >1500V

Power Consumption

About 120mA if the digital display is illuminated continuously (standard).
Can be ordered with 5-minutes auto-shut-off

Physical Characteristics

Height : 152 mm. (6.0 in.)
Width : 200 mm. (7.75 in.)
Depth : 70 mm. (2.75 in.)
Weight : 1.35 Kg (3.0 lb.)
Mounting : Four Mounting brackets, Standard height - 8mm. (0.31 in.)

Environmental Characteristics

Operating : -40 to +55 C
Storage : -60 to +100C
Humidity : <= 100% non-condensing


The above information is believed to be true at the time of printing. AMASS Data Technologies Inc. reserves the right to modify specifications without notice. All trademarks are owned by their respective companies.

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