Optical Utility Meter LED Pulse Sensor

£18.97 (Inc. VAT)
£15.81 (Ex. VAT)
50.00 Grams
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Optical pulse sensor for detecting LCD pulses from Utility Meters. 

The sensor can be easily stuck on to the front surface of any utility meter with an LED pulse output. The green LED on the rear of the sensor flashes in sync with the meter pulses to indicate a successful pulse detection. 

The Optical Pulse Sensor works by sensing a utility meter's pulsed LED output. Each pulse corresponds to a certain amount of energy passing through the meter. The amount of energy each pulse corresponds to depends on the meter. By counting these pulses the meters kWh value can be calculated.

Unlike clip-on CT based monitoring, pulse counting is measuring exactly what the utility meter is measuring i.e. what you get billed for. The pulse counting cannot provide an instantaneous power reading like CT based monitoring can. Where possible, we recommend using pulse counting in conjunction with CT monitoring. The emonPi and emonTx can simultaneously perform pulse counting and CT based monitoring.

In the case of an electricity meter, a pulse output corresponds to a certain amount of energy passing through the meter (kWh/Wh). For single-phase domestic electricity meters (eg. Elster A100c) each pulse usually corresponds to 1 Wh (1000 pulses per kWh). For water and gas meters they will usually be marked to show the quantity of water (litres/gallons) or of gas (cubic meters/cubic feet) that each pulse represents.


Compatible with emonPi (all versions) and emonTx V3.4 (firmware V1.8 and above, July 2015 onward)

With the removal of the RJ45 connector or use of RJ45 breakout and manual terminal block wiring the sensor will also work with the emonTH (firmware V1.6 and above) see emonTH wiki and emonTx V3.2 (firmware V2.0 or above) see emonTx V3.2 Wiki.



  • Pulse Output: TTL synchronised with the LED light pulses of energy meter.
  • Sensing Spectrum: IR to Light
  • Indicator: LED light at the top which synchronises with the pulses
  • Suitable for: all types of utility meters with pulse output: single-phase, multi-phase meters, water gas and electricity
  • Sticky attachment 
  • IP54 
  • Power supply: 3.3V - 5V 
  • Diameter: 22mm 
  • RJ45 Connector
  • 1m Cable


  • Current Consumption - no Pulse (sensor in darkness): 0mA @5V
  • Current Consumption - Pulse: 7.5mA @5V for duration of pulse (standard meter 100ms)
  • Output: Positive pulses output in TTL, is synchronized with the LED light pulses.

RJ45 Connector Pin-out:

  • RJ45 Pin 2 - VCC
  • RJ45 Pin 5 - GND
  • RJ45 Pin 6 - TTL Data

See Optical Pulse sensor Github Repo for further hardware resorces.

The cable can be extended using RJ45 Extender and standard RJ45 cable (not cross-over).


Optical Pulse Sensor Setup Guide

When installing the sensor, it is advisable to shield the meter and it from bright light as this can adversely affect readings.