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Volume 25 (Sep 28, 2004)
8-bit microcontrollers and their relentless support of our everyday lives (1/2)
Gas meters-Always watching over us
We use gas, water and electricity on a daily basis without ever really stopping to think about it. Yet these public resources are indispensable to our everyday lives. In this day and age when energy conservation is being advocated to preserve the global environment, we all would like to reduce the amount of resources we use to the extent possible and contribute to energy conservation. Are you aware that NEC Electronics' products are employed in meters that measure usage amounts for the resources we use each and every day?
Take, for example, gas meters. It is said that there are currently 50 million gas meters (including city gas and LP gas) installed throughout Japan. These gas meters not only measure the amount of gas we use for billing purposes, but they also play an important role in protecting us on a daily basis. Gas meters are also used to detect gas leaks and automatically cut off the gas supply when necessary. These functions are made possible by 8-bit microcontrollers (Figure 1).
Gas meters that use 8-bit microcontrollers are generally referred to as "microcontroller meters." There are also mechanical gas meters that do not employ microcontrollers, but because microcontroller meters have a number of advantages, e.g. they are virtually maintenance free and make it possible to use automatic inspection systems, they are expected to completely overtake their mechanical counterparts in the future.
8-bit microcontrollers and the support they provide for gas meters
Microcontroller meters are always watching over us in our everyday lives. Another feature of gas meters is that they have a monitoring function, which is the equivalent of an electric breaker. For example, if for some reason a gas leak occurs and there is abnormal gas discharge, the sensor detects the amount of gas being discharged and relays this information to the microcontroller. The microcontroller then issues a command for the isolation valve to be shut, and the gas supply is cut off. Moreover, if a fixed amount of gas flows for an extended period of time due to gas equipment having been left on or other reasons, the microcontroller meter automatically cuts off the gas supply just as it would in the event of a gas leak.
In addition, if a large earthquake occurs while gas is being used, the seismoscope built into the microcontroller meter will detect the intensity of the earthquake and relay this information to the microcontroller, which will then cut off the gas supply. However, even if a large earthquake is detected, the gas supply will not be cut off if gas is not being used at the time or there are no abnormalities such as gas leaks. Microcontroller meters are certainly capable of making very wise judgments.
In these ways, 8-bit microcontrollers monitor potentially dangerous situations around the clock and contribute to the safety of our living conditions.
Nowadays, there are even services that inform you of how much gas you have used via e-mail messages sent to your mobile phone or computer. There are also systems through which information such as utilization fees or the condition of the usage environment can be sent over a telephone line to the management center. Our lives are becoming increasingly safe and convenient because of the 8-bit microcontrollers that contribute to the services and systems like these.
The 8-bit microcontroller, which plays an active role inside microcontroller meters on a round-the-clock basis, also has another important feature-its power consumption is extremely low. Although microcontrollers used for gas meters are battery operated, the batteries only need to be changed every ten years, thereby making them a true success story in terms of power consumption reduction. Microcontroller meters are generally replaced every ten years. For the duration of those ten years, however, they can be used continuously and are virtually maintenance free.
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