ST AN2323 Application note
AN2323
Application note
Calibration procedure for STEVAL-IPE007V1
single-phase energy meter based on ST7FLite2x
Introduction
This application note describes the calibration procedure for STEVAL-IPE007V1, a singlephase power / energy meter with tamper detection.
Calibration is performed to minimize measurement errors and to increase the accuracy of
the meter.
Figure 1. STEVAL-IPE007V1 energy meter
July 2006 Rev 2 1/14
www.st.com
Contents AN2323
Contents
1 Calibration procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Hardware set-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2 Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2.1 Using firmware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2.2 Using the energy meter-GUI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
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AN2323 Calibration procedure
1 Calibration procedure
The procedure for meter calibration is explained below by firstly giving an overview of the
hardware set-up, and then by describing how to connect a calibration board and energy
meter GUI to update the firmware of the board.
1.1 Hardware set-up
Figure 2. Wiring Diagram
voltage
220 V
Input
AC Source &
phantom load
current
Energy
Meter
Sensor
Reference
Meter
Phantom Load Equipment
● AC Source and Phantom Load: As shown in Figure 2, this provides the AC source
and serves as a virtual load providing the current and voltage ratings as per the circuit
requirements.
● Energy Meter: The required voltage and current of the energy meter input is provided
by the phantom load. The basic current of this meter is 10 A with a maximum current
rating is 50 A. Operating voltage is 140 to 280 V.
As can be seen in the block diagram, there is an LED called the pulse count LED drawn
at the output of the meter. It glows at the rate of 3200 imp/kWh.
● Sensor: The sensor detects the current pulses of the pulse count LED and thereby
shows the error on the error calculator screen. As can be seen from the block diagram,
the sensor is connected to the error calculator.
● Reference Meter: This acts as a reference to the various measurements made with
the energy meter. The meter constant and the pulse count can be set with the help of
the reference meter. The meter constant is initially set to 3200 imp/kWh and the pulse
count is set according to the current at which the error is to be measured. For example,
Error
Calculator
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Calibration procedure AN2323
if the pulse count is set to 15, this means that after 15 current pulses, the error
calculator shows the deviation of the energy meter from the reference meter.
● Error Calculator: As the name suggests, this calculates the error and shows the value
on its screen. The Error is the deviation of the energy meter from the reference meter.
1.2 Calibration
There are two methods of meter calibration
● Using Firmware: This uses firmware and a calibration board linked to a PC, and
through the use of an Energy Meter GUI, calibrates the Energy Meter board. Before
doing this, the micro should have code inside. Refer to Section 1.2.1 on page 4.
● Using Energy Meter GUI: This method uses only a calibration board linked to a PC
and through the use of an Energy Meter GUI, calibrates the Energy Meter board.
Before doing this, the micro should have code inside. Refer to Section 1.2.2 on page 7.
1.2.1 Using firmware
Here, the firmware is used for calibration of the energy meter. The various steps to follow are
as follows:
1. First of all, the energy meter calibration board is connected with the PC Energy Meter
GUI using a serial cable. Then, the energy meter calibration board must be connected
to the meter. The connection diagram of the calibration board with the energy meter
and the PC is shown in Figure 3 below:
Figure 3. Connection diagram of calibration board with energy meter and PC
5V DC
Power Supply
PC
Serial
Cable
Serial
Calibration
Board
TDO RDI
GND1
GND2
V2
V1
Port
220V
TDO RDI GND
AC
Supply
V1
Energy Meter
2. A 5V DC supply should be connected to the GND2 and V2 pins of the calibration board.
For the calibration mode, a switch is provided on the energy meter which must be
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AN2323 Calibration procedure
pressed within 30 seconds of the supply of power to the unit. The energy meter then
switches into calibration mode.
3. Then, on the PC, it is necessary to open the Energy Meter GUI V1.x.x. This shown in
Figure 4 below:
Figure 4. Energy meter GUI
To operate the Energy Meter GUI:
4. First press Open, a window appears in which the baud rate should be selected as 9600
and COM port as COM1. Then, press the calibration switch on the energy meter and
click on the Check icon (upper middle), shown in Figure 4. With successful
communication, the message ‘Device is connected’ appears and voltage/current
offsets can be read. Otherwise, check the connections between the energy
meter/calibration board/PC and repeat the earlier steps.
5. The voltage/current offsets can now be read:
a) First, read the voltage offset. To do this, click on Offset icon (right side of close
icon). On the window that appears, click on the Select icon. Four gain multipliers
and a 220V reading are displayed. To read the voltage offset, click on 220V.
Press the calibration switch of the energy meter again and click on the Read icon
(bottom left) of the GUI. Offset values appear in the “Previous Values” column
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