Energy Measurement In a Complete Package
Looking for a way to quickly and easily measure power input or output, well these IC's might just fit the bill.
Analog Devices, Inc. have introduced the AD7751 and AD7755, additions to the company's family of power measurement data converters. These data acquisition processors are designed for metering active energy at the industry's lowest cost. They interface to 200 micro-ohm shunts and directly drive stepper motor counters. Other members of the AD775x family (soon to be introduced) will contain a serial port interface for bi-directional communication with a micro-controller or non-volatile memory.
The AD7751 is a highly accurate, fault-tolerant energy measurement integrated circuit, intended for use in energy meters on two-wire distribution systems. In addition to a voltage channel, the AD7751 has two current channels to allow for continuous monitoring of both the phase and neutral (return) current. If currents differ by more than 12.5%, a fault is indicated, but the AD7751 continues to bill accurately, using the larger of the two currents.
The AD7755 is a simplified, lower cost version of the AD7751. It is a highly accurate energy measurement integrated circuit with a wide dynamic range that uses one current channel and one voltage channel. The current channel interfaces nicely to current transformers, Hall Effect sensors, or 200 micro-ohm shunts.
These pin-compatible devices feature two sets of frequency outputs that consist of fixed-width pulse streams whose frequencies are pin-selectable. Their frequencies represent the product of current and voltage. Outputs span a broad range, from low-frequency outputs, suitable for stepping motors, to the higher frequency pulse streams, appropriate for calibration and test. Representation of 4-quadrant multiplication can be obtained by reading the magnitude-only outputs and monitoring the reverse-power logic output. The reverse-power indicator becomes active when negative power is detected.
The AD7751 and AD7755 were designed with a unique switched-capacitor architecture that allows a bipolar analog input on a single 5-volt power supply. Nonlinearity for either input is less than 0.05%, maximum. These products are enhanced with an integrated power supply monitor to ensure correct operation during power up and power down.
Fabricated on 0.6µ CMOS technology for low cost and low power consumption, the AD7751 and AD7755 are available in 24-pin SSOP and DIP packages.
The company's Web site address is http://www.analog.com/.