TWO AND THREE WIRE UTILITY DATA COMMUNICATIONS SYSTEM

摘要

A two wire/three wire utility data communicationssystem for remotely reading utility meter registers. Inthe two wire version, a hand-held reading unit isinductively coupled over two wires via a port locatedremotely from a meter register. Alternatively, a meterinterface unit (MIU) may be connected directly to theregister via three wires. Each register includes one ormore wheel position encoders. An AC interrogation signalis applied by the reading unit to encoder circuitry at themeter which powers the circuitry and causes the position ofeach encoder wheel to be read. In the two wire mode,register display information (e.g. the current meterreading) is transmitted back to the reading unit by varyingthe load (impedance) presented by the register side of thecircuit. This causes a corresponding variation of theamount of current drawn from the reading unit. Thecurrent-modulated signal is decoded by the reading unit andconverted into a register reading. The system can alsooperate in a three wire mode and read older fourteen wireencoded registers. Other features include remoteprogrammability of register characteristics, the ability tointerrogate multiple registers which share a common databus, verification of encoder wheel positions beforeaccepting a reading, real-time flow rate/leak detection,pulse output, and the capability of reading compound meters(i.e. meters having two registers to separately measurehigh/low flow rates).