typical tolerance of a digital counter
It is a copy of well known magazine article. Software included. Description:
Main Features
Displays power in Watts
Displays energy usage in kWh
Displays measurement period in hours
Displays energy cost in dollars and cents
Brownout detection and power switching
LCD module shows several readings simultaneously
Calibration for power, offset and phase
Adjustment of cents/kWh for cost reading
Adjustment of brownout voltage threshold, calibration, hysteresis & duration.
Optional delayed return of power after brownout is restored to normal voltage
Specifications
Wattage resolution 0.01W
Maximum wattage reading 3750.00W
Kilowatt hour resolution 1Wh (0.001kWh)
Maximum kWh reading 99999.999kWh
Cost/kWh resolution 0.1 cent
Maximum cost/kWh reading $9999.99
Cost/kWh setting from 0-25.5 cents
Timer resolution 0.1h (6 minutes)
Maximum timer value 9999.9h
Timer accuracy (uncalibrated) typically ±0.07%
Maximum load current 10A (15A surge)
Reading linearity 0.1% over a 1000:1 range
Frequency range of measurement 40Hz to 1kHz
Battery current drain during back-up 10mA
Accuracy Depends on calibration (error can be <0.5%)
Accuracy drift with temperature 0.002%/°C
Brownout voltage detection accuracy after calibration ±2%
Brownout return delay 18-24 minutes
Wattage calibration adjustment 0.0244% of reading per step (±2048 steps)
Zero Offset adjustment 0.12% of reading per step
Current monitoring resistance 1% tolerance, 20ppm/°C coefficient
Semiconductors
1 ADE7756AN Active Energy Metering IC (IC1)
1 PIC16F628A-20P programmed with wattmetr.hex (IC2)
1 LM2940CT-5 low dropout 5V regulator (REG1)
1 STP30NE06L logic Mosfet (Q1)
1 W04 1.2A bridge rectifier (BR1)
3 1N4004 1A diodes (D1,D2,D6)
3 1N914, 1N4148 switching diodes (D3-D5)