AVR465 datasheet(2/40 Pages) ATMEL

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AVR465

2566A-AVR-07/04

Overview

Power meters are sometimes referred to as energy meters and vice versa. Per

definition, (active) power is a measure of what is required (or consumed) in order to

perform useful work. For example, a light bulb with a 100W rating consumes 100

watts of active power in order to create light (and heat). Energy, per definition, is the

measure of how much work has been required over a known period of time. In the

light bulb example, leaving the bulb on for an hour it will consume 100W * 3600s =

360000Ws (watt-seconds) = 100Wh (watt-hours) = 0.1kWh (kilowatt-hours) of energy.

The meter described in this application note can be referred to as a power meter, an

energy meter or a kilowatt-hour meter. The Energy Pulse output (EP) is a ready

indication of active power, as registered by the meter; the frequency of the pulse is

directly proportional to active power. Integrating pulses over time gives active energy.

For storage purposes, the meter includes two pulse outputs (DPP and DPN) to

directly drive various display counters. All pulse outputs are easy to configure for any

reasonable rate. The default is 10.000 impulses per kilowatt-hour for the EP output

and 100 impulses per kilowatt-hour for the DPP/DPN pulses.

Not only pulse rates are readily adjusted; All measurement results can be calibrated

in the digital domain, removing the need for any trimming components. This includes

adjustments to compensate for phase delays in current transformers. The calibration

event can be automated, removing the time-consuming manual trimming required in

traditional, electromechanical meters. Digital calibration is fast and efficient, reducing

the overall production time and cost. Calibration coefficients are safely stored in the

internal EEPROM, further reducing the need for external devices.

The brain of the meter is the firmware, which is provided open source. Although it

includes all the functionality required for a tamper-proof, single-phase meter, it can be

modified and updated at any time. Even in the field. The firmware is entirely written in

C, which makes modifications easy to implement. Integrity and intellectual property

are yet easy to secure using Lock Bits of the AVR microcontroller.

Meter Hardware

The energy meter hardware consists of a power supply, an analog front end, a

microcontroller section, and an interface section.

The meter described in this application note connects to high currents and high

voltages. High currents and high voltages may be hazardous, even lethal. Hence, the

meter should be operated by qualified technicians only. Atmel takes no responsibility

for any consequence that may result from the use of this document or the application

described herein.

Warning:

Shock Hazard

AVR465 Datasheet(PDF) 2 Page - ATMEL Corporation