LED Pulse Sensor

Picture of LED Pulse Sensor

The LED pulse sensor (LPS) picks up the light output pulses from the flashing LED consumption indicator on an energy meter and converts this into an electrical pulse. The electric pulse can then be used in a suitable logger to monitor energy usage.

The LPS is designed to work with the Crucible Technologies Meter Logger 100 and 6C products.

Benefits of using the LED pulse sensor

  • Easy attachment
  • Non-intrusive
  • Measures exactly the same energy usage as the meter
  • Low cost
  • Only one needed on 3-phase electricity meters

Current clamps are the traditional method of measuring electrical energy consumption. However they introduce a number of inaccuracies. They have a tolerance when measuring the current and one would need to measure the voltage as well to calculate the actual power used. The LED pulse sensor measures exactly what the revenue meter measures.

Versions

The LED pulse sensor comes in two versions: passive and active. The key differences between the two versions are described in the following table:

Passive Active
2 wire connection (signal and ground)
Does not require external supply voltage
3 wire connection (5V, signal and ground)
Requires 5V supply
Every time the LED on an energy meter pulses, the resistance between the signal and ground connections drops to around 2k ohm
This means that if the pull-up resistor on the input of the data logger is around 10k, the voltage on the input is around 20% of the supply voltage
Every time the LED on an energy meter pulses, the voltage between the signal and ground connections drops to less than 0.2V
This means that the voltage on the input of the data logger is independent of the pull-up resistor
The only current the passive LPS draws from the input of the data logger is when the LED pulses and this is typically 0.3 mA (based on a 10k pull-up to a 3.3V supply) The active LPS draws current from the 5V supply when the LED flashes (2.3mA) and current from the input of the data logger when the LED flashes of typically 3.3mA (based on a 1k pull-up to a 3.3V supply). This second current reduces with increasing pull-up resistance.
The alignment of the passive LPS with the LED of the energy meter can be quite critical in order to achieve the lowest "on" resistance The alignment of the LPS with the LED of the energy meter is much less critical
The width of the pulse from the LPS to the data logger can be significantly less than the LED pulse from the energy meter and is dependent on alignment and value of pull-up resistance The width of the pulse from the active LPS to the data logger is close to width of the LED pulse from the energy meter and is more tolerant of alignment and value of pull-up resistance

Installation

The LED pulse sensor is extremely easy to install. The black cross on the unit assists the user to line up the optical sensor with the LED on the energy meter. The LED pulse sensor is provided with a sticky pad which is used to securely attach it to the meter.

The photograph at the bottom of this page shows the LED pulse sensor installed on a typical 3-phase electricity meter.

Performance Data

The following table shows the cumulative electricity usage recorded by a Meter Logger 100 & LED pulse sensor installed at our premises versus the reading on the meter itself. As can be seen, to within the display resolution of the meter (whole kWh's), there is complete agreement.

Date Meter (kWh) ML3P+LIGHTSENS
3 Mar 2014 66 66.06
4 Mar 2014 141 140.7
6 Mar 2014 426 425.78
10 Mar 2014 777 777.45
13 Mar 2014 1373 1372.5
17 Mar 2014 1735 1735.7
25 Mar 2014 2687 2687.7

Wiring Information

The LPS is supplied with 1 meter of cable.

The passive LPS has two wire cable where the more negative side of the two wires is marked with a black line.

The Active LPS has a three wire cable;

Red: 5V
White: Signal
Black: Ground

Additional Technical Information

When connected to a Meter Logger 100 or 6C, the cable connecting the LED pulse sensor can be up to 20m in length, allowing the Meter Logger to be conveniently located.

When using the passive LPS, it is recommended that the electronics on the data logger should have a pull up resistance of at least 10kohms to allow reliable detection of the pulse signal.

Dimensions

The LED pulse sensor is approximately 10mm deep.

Light sensor dimensions

Delivery Leadtime

Wherever possible, orders are fulfilled from stock. However for larger quantity (10 or more units) orders, a delivery leadtime of 3-4 weeks may be experienced for part or all of the order.

Alternate picture of LED Pulse Sensor Alternate picture of LED Pulse Sensor

Description Code Price (ex Vat) Select
Add to Basket
LED Pulse Sensor LIGHTSENS £16.50
Active LED Pulse Sensor ACTIVELPS £19.30

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