A Tamper-resistant Watt-hour Energy Meter Based On The Ad7751 And Two Current Sensors
Digital circuits

A Tamper-resistant Watt-hour Energy Meter Based On The Ad7751 And Two Current Sensors

By internum


This application note describes a low-cost, high-accuracy watt-hour meter based on the AD7751.

This application note describes a  low-cost, high-accuracy watt-hour  meter  based  on  the  AD7751.  The  meter described is intended for use in single-phase, two-wire distribution systems. However, the design CAN easily be adapted  to suit specific  regional  requirements, e.g.,  in the United States power  is usually distributed  to  residential customers as single-phase, three-wire.

The AD7751 is a low-cost, single-chip solution for electrical Energy Measurement The most distinctive feature of the AD7751 is that it continuously monitors the phase and neutral (return) currents. A FAULT condition occurs if the two currents differ by more than 12.5%. Power calculation will be based on the larger of the two currents. The meter calculates power correctly even if one of the two wires does not carry any current. AD7751 provides an  effective way  to  combat  any  attempt  to  return  the current through earth, a very simple yet effective way of meter  tampering.  The  AD7751 is  comprised  of  two ADCs,  reference  circuit,  and  all  the  signal  processing necessary for the calculation of real (active) power. The AD7751 also includes direct drive capability for electrome chanical Counters (i.e., the energy register) and has a high-frequency  pulse  output  for  calibration  and  communications purposes.

A Tamper-resistant Watt-hour Energy Meter Based On The Ad7751 And Two Current Sensors
A Tamper-resistant Watt-hour Energy Meter Based On The Ad7751 And Two Current Sensors circuits

This application note should be used in conjunction with the AD7751 data sheet. The data sheet provides detailed information on the functionality of the AD7751 and will be referenced several times in this application note.

2516 19 September 2009

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