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Elpro 505U Radio Telemetry Transmitter

Elpro 505U Radio Telemetry Transmitter

Quick Overview

The 505U radio telemetry module is an economical solution for the remote monitoring of process signals. The 505U can connect to digital, pulse or analogue signals from process transducers, and transmit these signal values up to several kilometers by radio. The 505U is contained in a heavy duty, weatherproof IP65 enclosure.
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Easy To Use 
The 505U has an internal low power radio transmitter which operates on unlicensed radio channels in the UHF band. A radio licence is not required for the 505U in most countries. The 505U has an operating range of several kilometres. It is suitable for monitoring in utility industries such as electricity, water and gas; and because of its low price, it is also a cost effective solution for short range applications in factories and plants. 

Mode of Operation 
The 505U transmits the value of the input signal whenever the signal changes, and after a pre-configured time. Each transmission message includes error-checking to confirm the validity of the message. At each transmission, the 505U may be configured to repeat the transmission several times to ensure that the transmission is received correctly. The input signal is then output either as an identical signal or across a serial data link (RS232 or RS485). 

Extremely Low Power Consumption
The power consumption of the 505U is very small as it conserves power by reverting to ”sleep” mode between transmissions.  The 505U can be powered from an external 12 VDC supply, or it may be optionally fitted with internal AA batteries which will power the unit for more than four years. The 505U unit provides an internal alarm on low battery voltage - this alarm may be transmitted by radio. 

Weatherproof IP65 Enclosure
The 505U is enclosed in a heavy duty painted aluminium enclosure, weather-proofed to IP65.  Signal and power connections to the unit are made via a weatherproof connector.

Compatible with 105U
The 505U is compatible with the 105U range of radio telemetry units*; 105U units may be used to output the process signals, or act as a network master unit to connect to an intelligent host such as a PC or PLC. 105U units may also be used as repeaters to extend radio range - up to five intermediate 105U modules may be used as repeaters in any radio path. More than 10 000 505U units may operate together in a single system. (*Refer to 105U product literature) 

The 505U unit will accept digital, pulse and analogue input signals, and will transmit the value of an input when the value changes. The input value is also transmitted if the signal has not changed within a pre-configured update time (configurable 1 minute to 5 days). Pulse signals use the same input connection as digital inputs.

Alarm and Status Signals
The 505U will connect to digital inputs such as alarm or status signals which are voltage free contacts or 0-5 VDC signals. Whenever the digital signal changes (off to on, or on to off) the 505U will interrupt its sleep mode and immediately transmit the signal value. For digital inputs, there is a separate update time when the digital signal is active (on). For example, an alarm input may update only every day when it is inactive, but update every minute when it is active. This feature allows a large number of 505U units to share the same radio channel.  As well as the external digital inputs, there are two internal digital “inputs”  - low battery voltage and analogue setpoint status. 

Pulse Signals 
The 505U will accept pulse signals up to 100 Hz, suitable for metering applications. Whenever a pulse input is detected, the 505U will interrupt its sleep mode and increase its internal pulse counter. The totalised pulse count is transmitted whenever the count has changed by a pre-configured amount. Transmissions will also occur after the update time.  By transmitting the totalised pulse count, the 505U ensures that individual pulses are not lost, Should a radio transmission not be successful, the pulse count is still held in the 505U, and the totalised value will be updated on the next transmission. Change transmissions may be disabled if the pulse rate exceeds a pre-configured amount, to prevent the radio channel becoming congested during peak periods. 

Analogue Signals
The 505U-2 model has one 0-20 mA (0-10 / 4-20 / 0-20 mA) analogue input. The analogue signal may be externally or loop powered - the 505U generates a 12VDC loop supply. During sleep mode, the loop supply is switched off. After a pre-configured sleep period, the analogue loop supply is activated, and the analogue measurement is taken. A warm-up time may be configured to allow the analogue loop to stabilise before the measurement is taken. If the sleep period is set to zero, then the 505U does not revert to sleep mode, and it will continually measure the analogue signal - note that this is only suitable where the 505U is powered from an external supply. Once the analogue measurement is taken, the 505U will transmit its value if it has changed since the last measurement. A sensitivity value is configured (0.8 - 50%) to determine the minimum change to cause a transmission. In addition, the analogue value will be transmitted if the update time has been exceeded.  Configurable setpoint values may be used to generate an internal alarm status which may also be transmitted. 

Configuration and Diagnostics
Configuration is easily performed by connecting a PC to an RS232 port on the 505U module.  The configuration software which is provided with the unit, also includes diagnostic functions.



  • Environmental -20 to 60degC 0 - 99% RH
  • EMC compliant 89/336 EEC, AS3548
  • Housing - IP65 painted aluminium enclosure 160 x 64 x 36 mm
  • Weatherproof connector for external connections.
  • BNC connector for aerial or coaxial cable connection.
  • LED indicators - Radio TX, Operation OK
Power Supply
  • External supply 11.5-15.0 VDC over voltage/reverse power protected.
  • Power consumption (12VDC) -
    quiescent (sleep mode) 120µA
    operating mode 10mA + analogue loop
    during radio transmission (100 msec)
    170mA @ 250mW
    100mA @ 100mW
    50mA @ 10mW
  • Internal battery supply (505U-x-B only)
    3 x AA lithium 3.5V 6 amp-hour nominal 4.1 year service life
    2 x AA lithium 3.5V 4 amp-hour nominal 2.7 year service life
    3 x AA alkaline 1.5V 2 amp-hour nominal 1.4 year service life
  • Power consumption (internal battery supply)
    quiescent (sleep mode) 2.9mA-hour per day
    analogue sample (5 sec warmup, 20mA) 120µA-hour during radio transmission
      22µA-hour @ 250mW
      15µA-hour @ 100mW
      10µA-hour @ 10mW 
  • Analogue loop supply internally generated 10-12VDC, 50mA
  • Internal monitoring of battery low voltage status - may be transmitted to remote modules as an “input”.
  • Power consumption increases for pulse inputs > 1Hz.
Input Types
Power Supply
Battery low Volts
Digital/Pulse Input
  • 505U-1 one input
  • 505U-2 two inputs
  • suitable for voltage free contacts / NPN
Digital Inputs
  • transmitted as digital status, debounce time 0.5 secs.
  • status transmission on change of input signal and on time elapsed since last transmission - update time period 1 min - 5.3 days, a separate update time may be configured for faster updates when the digital input is “on”
Pulse Input
  • max rate 100 Hz (5 msec on time), transmitted as pulse count transmissions occur when count change exceeds configured amount, or on time elapsed since last transmission - update time 1 min - 5 days - change transmissions may be suspended if pulse rate exceeds a configured value to reduce radio traffic.
  • Up/Down Pulse Input (505U-2 only) - The two pulse inputs may be configured to a single count, to suit quadrature or incremental shaft encoder transducers.
Analogue Input (505U-2 only)
  • 0 to 20 mA (4 - 20mA, 0 - 10mA) “floating” differential input
  • common mode voltage 15V
  • resolution 12 bit
  • accuracy < 0.1%
  • analogue measurement continuous or sampled - sample time configurable 1 min - 5 days
  • transducer warm-up time configurable 1 - 59 sec
  • analogue value transmitted on change of input signal or time elapsed since last transmission - change sensitivity configurable from 0.8 to 50%, update time configurable from 1 min - 5 days
Setpoint Status
  • high and low setpoints generate internal digital status - setpoint status sets (on) when analogue value < low setpoint and resets (off) when analogue value > high setpoint status transmitted as per digital input
Serial Port
  • RS232 DB9 female DCE, used for configuration and diagnostics
Radio Transmitter
  • Synthesised transmitter
  • Frequency range 405 - 490 MHz.
  • Channel spacing 12.5KHz
  • Frequency configurable range 10MHz
  • Transmitter power (factory set) -
     500mW with 3dB aerial
     100mW / 10mW 0dB aerial 
  • For 2 x AA battery supply, max power is 100mW 
  • Conforms to EN 300 220, MPT1329, AS4268.2, NZ RFS29 
  • Line of sight range -
    10km (6 mi) @ 500mW
    5km @ 100mW
    2km @ 10mW 
  • Each transmission may be configured to be sent 1 to 5 times.
Product Types
  • External 12VDC supply only -
       505U-1-E (one digital/pulse input)
       505U-2-E (two digital/pulse inputs plus one analogue input) 
  • Internal battery supply only (batteries not included) -
     505U-1-B (one digital/pulse input)
     505U-2-B (two digital/pulse inputs plus one analogue input)

Availability: Stock Item


Components / Downloads

For further information, technical advice, or a quotation please call or email us. If you are not sure which product you need one of our technical sales advisors will be happy to discuss your application. We also accept company purchase orders by fax or post. Credit card orders can also be placed over the phone for any product.

Elpro 505-u radio telemetry unit, 2 digital or pulse inputs, 1 analogue input, power supply external 12v DC.
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