CHAPTER 2
LITERATURE REVIEW
2.1 Introduction
This literature reviews give the basic idea and information of other already done project that has similarity to my project. It also reviews the related hardware and software
theory that need to be use in Energy Meter Data Logger Project.
The digital energy meter or kWh meter developments are very important for today energy monitoring or metering to measure the usage of energy that has been use for the
specific costumer. To maintain the accuracy that energy had been used, a proper system must be made so it can measure accurately within time to time with minimal error. The
energy meter system must have both single phase measurement and three phase measurement for higher energy usage facilities.
2.1.1 Single Phase Microcontroller Based Energy Meter
Based on this project its totally electronic single phase energy meter for residential use and using the Microchip Technology Inc PIC family to do it. The design takes into
consideration the correct operation in the event of an outage or brown out, by recording the energy consumption in EEPROM memories internally available in the microcontroller. By
using the EEPROM memory, after the energy supply restored from failure the meter can gather back the data taken before the supply failure so the data can be use to display the
overall energy consumption. The basis equation for calculating the energy for inte rval ∆t
= t2 - tl is given below:[1]
� = � �
2 1
2.1
The AD converter for microchip use in this project is 8 bits and the sampling frequency of 1,082kHz. While energy measured are compared with reference value Eref,
for 1kW load and 100 period of 924µs the Eref is given below: �
= 100
∙ 924� ∙ 1000� 3600
= 0.00002567 ��ℎ 2.2
While voltage measuring and sensing circuit, they use basic voltage divider circuit as show in Figure 2.1 and second order low pass filter to eliminate any DC component
offset [1].
Figure 2.1 Voltage Sensing Circuit [1]
Figure 2.2 Current Sensing Circuit [1]
To measure current, the operational amplifier circuit in Figure 2.2 is used. Other circuits that are used for this project such as Oscillator circuit for determining the PIC
clock frequency. Then, Supply voltage level detector also needed to enable the EEPROM memory when the supply voltage to PIC is drop less than 4.2V so the energy consumption
can be stored to the memory. The Disabling circuit are also used to shut down the PIC if supply voltage becomes less than pre-defined level to prevent PIC from working in low
voltage level. After the project has completely done the hardware must be tested and the result are shows in Table 2.1.
Table 2.1 Meter Precision Test Result [1] Load
Actual Time Measured Time
Error
1kW 3600s
3643s 1.19
0.75kW 4800s
4769s 0.65
0.5kW 7200s
7304s 1.44
0.33kW 10800s
10855s 0.5
0.25W 14400s
14635s 1.63
0W 36s
36.01 0.03
The precision experimentally obtained for this new meter better than 97. This value is compatible with the electromechanical meters in the market. In addition, the
process of reading the energy consumption is facilitated by the four-digit display, which is simpler than the analog meters. The calibration process is implemented by using a RS232
interface from any microcomputer that runs the Windows Terminal program. This communication form is simple, since it makes use of the basic configuration available in
the microcomputers [1].
2.1.2 Data Logging Solution for Digital Signal Processors
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