You can recognise a meter that can be read with an optical sensor by the mirror on the counter. This small mirror is mostly positioned in the number 6, 8, 9 of 0. The optical reader uses the reflection of the 0, 6, 8 or 9 as it speeds past to count the number of rotations that your meter is making. In this way, it counts the number of litres of water, or m³ of gas, being consumed. You can also use the optical sensor on meters with revolving hands. In this type of counter, the hand interrupts the light beam of the optical sensor as it rotates past. In this way, the sensor counts the number of revolutions that the hand makes and therefore also the volume of gas or water being consumed. If your meter has visibly moving parts, such as hands or a mirror or wheels with a built-in cover, then you use an optical sensor.
The water meter below has rotating hands and even has a reflective surface on one of the hands.
The gas meter below has rotating hands.
The image below shows a meter with a reflective ‘6’ on the counter.
The meter below does not have any reflective numbers on the counter, but instead has an opening in the side into which the sensor can be inserted. This kind of meter has a built-in magnet that rotates every time a volume of water or gas is consumed. The magnetic sensor senses when the built-in magnet at the end of the opening inside the meter comes past. In this way, the volume of water or gas consumed is registered.
You can therefore recognise meters that can be read with a magnetic sensor by the small hole below the counter on the left or right. Readings can be taken from the majority of gas metres with an optical sensor and from the majority of water meters with a magnetic sensor.