In most large cities, utility companies or closed communities run piped Water and Liquefied Petroleum Gas, LPG, to all homes. The usage of such fluids is monitored by the meters that are connected to the line. This requires a person from the company to come over during the end of each billing period, to take readings and prepare the bills. To save costs on these visitations, utility companies started looking at ways and mean to capture readings directly, via the Internet.
This is where Magnet Sensors and Reed Sensors help. To make an existing analog meter generate digital output readings that can be transmitted, a square wave pulse should be generated for every turn of the smallest digit. The way to get this done is to embed a tiny magnet within the last digit and place a reed sensor just near it so that an on and an off is generated for every turn of this smallest digit on the meter. This sort of pulse counting application requires careful selection of AT band and magnet. Once the square is generated, it is correlated to actual consumption and can be transmitted to the utility company.
For such applications, specially designed reed switches with high spring back forces are suitable for use inside the reed sensor or magnet sensor. Even if the meter is unused for periods of up to three months and the reed sensor stays closed for all this time, the contact can easily open up and continue to work once the meter dial starts turning.