Monitoring Natural Gas Usage
http://phk.freebsd.dk/Gasdims/
"Somebody, somewhere, had this vision of electronic meter reading, and managed to arrange for all meters to have a pulse output, probably costing all gas-customers extra for the feature, but tickle me with a pole if that will ever be implemented."
"But I did notice something else: it is implemented optically rather than mechanically because the zero on the least significant digit i a shiny metalic oval rather than a painted white numeral."
"I used a standard parallel port to interface to the computer so getting power for the LED was just a matter of using enough of the data outputs. "
"The phototransistor was not quite strong enough to pull down the "ACK" input of the parallel port so an extra transistor was needed as driver for that. A randon NPN from the junkheap did the trick."
"In FreeBSD the "pps" driver provides access to the PPS-API which can be used to report the exact time of the pulses on "ACK" pin of the parallel port."
My comment:
Same kind of ideas can be used for reading any similar type meter. For example rotating electrical consumption meters or the flashing LED in newer electronic electrical meters.
