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Design Guide: TIDA-010037

High-Accuracy Split-Phase CT Electricity Meter Reference
Design Using Standalone ADCs

Description

This reference design implements Class 0.1 split-
phase energy measurement using high-performance,
multi-channel analog-to-digital converters (ADC). The
ADC samples current transformers (CT) at 8 kHz to
measure the current and voltage of each leg of the AC
mains. The reference design achieves high accuracy
across a wide input current range (0.05–100 A) and
supports high sampling frequencies necessary for
power quality features such as individual harmonic
analysis. An ADC sample rate of 32 ksps can be
acheived by disabling some software functions.
Independent ADCs provide flexibility in the choice of
metrology microcontrollers compared to integrated
SoCs. This reference design uses a SimpleLink

™

ARM

®

Cortex

®

-M4 host microcontroller for metrology.

The necessary software functionality is implemented
in the ADC Energy Metrology library. The software
library can be compiled with Code Composer Studio

™

or IAR Embedded Workbench

®

.

Resources

Design Folder

,

Product Folder

,

,

Product Folder

Product Folder

ADC Energy Metrology Library

Software

support experts

Features

• Split-phase metrology for electricity meters that

meets ANSI C12.20 Class 0.1 active energy
accuracy requirements across 10000:1 input range

• Active and reactive energy and power, root mean

square (RMS) current and voltage, power factor,
and line-frequency calculations

• Isolated RS-232 and RS-485 with 5-kV

RMS

isolation

• Communications module expansion with current

limit and overvoltage and undervoltage protection

• Tested across 50 mA to 100 A input range
• High active energy accuracy still obtained when

ADC sample rate increased to 32 ksps

• Software for energy metrology and displaying

results on a Windows

®

PC GUI.

Applications

•

Electricity meter

•

Power quality meter

•

Power quality analyzer

6'

ADC

6'

ADC

-

Source From Utility

Load

Phase A

Phase A

N

e

u

tra

l

+

+

-

ADS131M04

N

e

u

tra

l

SCLK

DIN

DOUT

DRDY

VCC

GND

6'

ADC

6'

ADC

-

+

+

-

SPI MISO

GPIO

Interruptible GPIO

SPI CLK
SPI MOSI

CLKIN

VDD

GND

SMCLK

RESET VCC

CSn

Phase B

Phase B

I

A

I

B

CT

CT

+

-

TOTAL

A

B

kWh

VCC

GND

Lx

MSP432P4111

GPIO

GPIO

VCC

GND

ISO-DVCC
ISO-GND
ISO-ACTIVE

ISO-REACTIVE

ISO7720

DVCC

DVSS

Active

Reactive

TPS3840

VCC

RESET

CT

GND

RST/NMI

TPS709

GND

VCC

GND

5V_IN

TVS1800

TPS25921L

5V_LMT

Lx/PMAP GPIO

UART2 TX

UART2 RX

RS-232

Connection

ISO7731 B

VCC

GND

TPS709

TRS3232E

DTR

RTS

RGND

RS232_VCC

RS232_GND

Board

Header to

External

Radio/Radio

Module

5V_LMT

GND

Lx/PMAP GPIO

Lx/PMAP GPIO
Lx/PMAP GPIO

THVD1500

RS-485

Connection

GPIO

RE
WE

RGND
VCC3

V

B

V

A

Description

TIDUEM8B – MARCH 2019 – REVISED FEBRUARY 2021

Submit Document Feedback

High-Accuracy Split-Phase CT Electricity Meter Reference Design Using

Standalone ADCs

1

Copyright © 2021 Texas Instruments Incorporated

1
2
3
...
»

Summary of Contents for TIDA-010037

Page 1: ... 0 1 active energy accuracy requirements across 10000 1 input range Active and reactive energy and power root mean square RMS current and voltage power factor and line frequency calculations Isolated RS 232 and RS 485 with 5 kVRMS isolation Communications module expansion with current limit and overvoltage and undervoltage protection Tested across 50 mA to 100 A input range High active energy accu...

Page 2: ...used it is necessary for the current sensors to be isolated so they can properly sense the current drawn from the two different lines without damaging the ADC As a result current transformers which inherently have isolation have historically been used for the current sensors for split phase two phase and three phase electricity meters In this reference design Class 0 1 split phase CT based energy ...

Page 3: ...eparate host MCU or processor as is done in this design A couple of the parameters commonly measured by power quality meters and power quality analyzers are voltage and current harmonics For the most accurate harmonic calculations coherent sampling should be implemented One way of implementing coherent sampling is to vary the sampling clock based on the Mains frequency The standalone ADC in this d...

Page 4: ...re RMS current and voltage Power factor Line frequency Update rate for measured parameters Approximately equal to 1 second Communication options LCD PC GUI via 5 kVRMS isolated RS 232 or isolated RS 485 External radio or radio module connected to the Comms header 5 V rail current limited to 1 6 A with manual reset after overcurrent thermal shutdown event Measured power failure detection threshold ...

Page 5: ...ge Configuration 6 ADC 6 ADC Source From Utility Load Phase A Phase A Neutral ADS131M04 Neutral SCLK DIN DOUT DRDY VCC GND 6 ADC 6 ADC SPI MISO GPIO Interruptible GPIO SPI CLK SPI MOSI CLKIN VDD GND SMCLK RESET VCC CSn Phase B Phase B V IA IB CT CT TOTAL A B kWh VCC GND Lx MSP432P4111 GPIO GPIO VCC GND ISO DVCC ISO GND ISO ACTIVE ISO REACTIVE ISO7720 DVCC DVSS Active Reactive TPS3840 VCC RESET CT ...

Page 6: ... also supports communication using external radios or radio modules that are connected to the J11 and J12 headers of the board The J11 header connects the P7 0 P7 1 P7 2 and P7 3 port pins which can be configured as port mappable GPIO pins if the LCD is disabled Software can be added to the MSP432 MCU to communicate to an external radio or radio module by configuring any of these four pins as comm...

Page 7: ...e ADS131M04 divides this clock by two and uses this divided clock for its delta sigma modulator clock When new ADC samples are ready the ADS131M04 asserts its DRDY pin to alert the host MCU that there are new ADC samples that are available Since the ADS131M04 device can accept a clock with a wide frequency range the device itself can also be used for applications that require coherent sampling 2 2...

Page 8: ...otection for all systems and applications powered from 4 5 V to 18 V For hot plug in boards the device provides in rush current control and programmable output ramp rate The TPS25921 device integrates overcurrent and short circuit protection The precision overcurrent limit helps to minimize over design of the input power supply while the fast response short circuit protection immediately isolates ...

Page 9: ... a customer s system instead of RS 485 only two isolation channels are needed so a two channel ISO7721B device could be used to reduce cost instead of using the three channel ISO7731B device keep in mind that these two devices are not pin to pin compatible Each isolation channel has a logic input and output buffer separated by a double capacitive silicon dioxide SiO2 insulation barrier This chip s...

Page 10: ... protection over the lifetime of the product TI tests the TVS1800 device against 5 000 repetitive surge strikes at high temperature with no shift in device performance In this design the TVS1800 device is placed at the input of the TPS25921L device to protect it from any transient voltages that would occur from the TPS25921L disconnecting the load during overcurrent overvoltage or undervoltage eve...

Page 11: ...MSP432 MCU from the 5 V applied at J4 so that only one input rail is necessary If the voltage provided to J4 is below 4 036 V based on internal undervoltage lockout voltage or above 5 78 V the source at J4 will be disconnected from the load at J3 In addition if the current drawn from the load exceeds 1 6 A thermal shutdown is eventually triggered and the source is disconnected from the load During...

Page 12: ...o meet this input voltage specification the current and voltage inputs must be divided down In addition the ADS131M04 device can sense voltages down to 1 2 V therefore AC signals from mains can be directly interfaced without the need for level shifters This subsection describes the analog front end used for voltage and current channels 2 3 1 4 1 Voltage Measurement Analog Front End The nominal vol...

Page 13: ...rs R91 and R92 and an RC low pass filter R94 R95 C97 C98 and C99 that functions as an anti alias filter There are also footprints U21 and U22 that can be replaced with the TVS0500 for supplemental protection from surges if required As Figure 2 6 shows resistors R91 and R92 are the burden resistors which are in series with each other For best THD performance instead of using one burden resistor two...

Page 14: ...2 MCU has a port mapping controller that allows a flexible mapping of digital functions to port pins The set of digital functions that can be ported to other pins is dependent on the device For the MSP432 device in particular the SPI clock SOMI and SIMO functionality of the EUSCIB0 SPI module are all available options to port to ports P2 P3 and P7 In addition the SMCLK clock output is also availab...

Page 15: ... 2 3 2 1 6 Direct Memory Access DMA The direct memory access DMA module transfers packets between the MSP432 MCU and ADS131M04 device with minimal bandwidth requirements from the MSP432 CPU Two DMA channels are used for communicating to the ADS131M04 One channel channel 0 is used to send data to the ADS131M04 and the other channel channel 1 is used to receive data from the ADS131M04 Once a complet...

Page 16: ... disabled and a reset command is sent from the MSP432 MCU to the ADS131M04 via SPI Interrupts are then re enabled and the MSP432 MCU sends commands to the ADS131M04 to configure its registers At this point note that the modulation clock is not output by the MSP432 MCU yet which means that sampling is not started yet By sending commands to the ADS131M04 to initialize the ADS131M04 registers the ADS...

Page 17: ...ne to Neutral Voltage For a balanced split phase system each line to neutral voltage should be half of the line to line voltage In the one voltage configuration of this design only the line to line voltage is measured The line to line voltage readings are divided by two this division is done automatically by following the calibration process to get the line to neutral voltages of each phase As a r...

Page 18: ...s Provide a pulse on MSP432 GPIO pin connected to TPS25921 V 1 UVLO pin Figure 2 9 Foreground Process The initialization routines involve the setup of the MSP432 general purpose input output GPIO port pins and associated port map controller MSP432 clock system MSP432 USCI_A0 for UART functionality MSP432 RTC module for clock functionality MSP432 LCD MSP432 DMA ADS131M04 registers and MSP432 metrol...

Page 19: ...are associated with each other for the other mapping Otherwise for the one voltage configuration each voltage current mapping has the same voltage for each mapping since only one voltage is measured In the one voltage configuration the line to line voltage measurement is associated with the line A current for the first mapping and the same line to line voltage measurement is associated with the li...

Page 20: ...tive power measurements from other phases and the neutral PREACT_offset ph Offset used to subtract effects of crosstalk on the reactive power measurements from other phases and the neutral Note that for reactive energy the 90 phase shift approach is used for two reasons 1 This approach allows accurate measurement of the reactive power for very small currents 2 This approach conforms to the measure...

Page 21: ...e one for each phase and one for the cumulative of the phases Within each set of buffers the following energies are accumulated 1 Active import energy active energy when active energy 0 2 Active export energy active energy when active energy 0 3 React Quad I energy reactive energy when reactive energy 0 and active power 0 inductive load 4 React Quad II energy reactive energy when reactive energy 0...

Page 22: ...ck Cycles OSR N 2 OSR N 3 Sample Iphx N 1 and Vphx N 1 OSR Modulation Clock Cycles Request Packet with Iphx N and Vphx N Packet with Iphx N and Vphx N Per Sample DSP with Iphx N 1 and Vphx N 1 Sample Iphx N 2 and Vphx N 2 OSR Modulation Clock Cycles Request Packet with Iphx N 1 and Vphx N 1 Packet with Iphx N 1 and Vphx N 1 Per Sample DSP with Iphx N and Vphx N Figure 2 10 Voltage and Current Samp...

Page 23: ...DMA module instead of it being done by the software Figure 2 12 shows the packet that is transmitted by the DMA of the MSP432 MCU and the response packet from the ADS131M04 that is received and assembled by the DMA as well The transmission and reception packets contain six words where each word is three bytes long MSP432 Transmit Command N 1 Dummy Write 3 bytes 0x000000 Dummy Write 3 bytes 0x00000...

Page 24: ...ry because the word size was selected to be three bytes in this design If the word size was selected to be two bytes or four bytes instead the software CRC calculation would not be needed since there would be an even number of bytes Figure 2 13 shows the code snippet for calculating the CRC over 15 bytes by using the MSP432 CRC module and software Figure 2 13 Code Snippet for Using the CRC Module ...

Page 25: ... the background process just calculated and the background process uses a new empty set to calculate the next set of dot products Whenever there is a leading edge zero crossing to voltage transition on a voltage channel the per_sample_dsp function is also responsible for updating the corresponding frequency in samples per cycle of the phase The following sections describe the various elements of e...

Page 26: ...a zero crossing The resultant cycle to cycle timing goes through a weak low pass filter to further smooth out any cycle to cycle variations This filtering results in a stable and accurate frequency measurement that is tolerant of noise 2 3 2 3 2 LED Pulse Generation In electricity meters the energy consumption of the load is normally measured in a fraction of kilowatt hour kWh pulses This informat...

Page 27: ...ther phase shift The user must compensate the relative phase shift between voltage and current samples to ensure accurate measurements The implementation of the phase shift compensation consists of an integer part and a fractional part The integer part is realized by providing an N samples delay The fractional part is realized by a one tap finite impulse response FIR filter that interpolates betwe...

Page 28: ...autions when operating CAUTION High Voltage Electric shocks are possible when connecting the board to live wires The board must be handled with care by a professional For safety use of isolated test equipment with overvoltage or overcurrent protection is highly recommended Hardware Software Testing Requirements and Test Results www ti com 28 High Accuracy Split Phase CT Electricity Meter Reference...

Page 29: ... A is made The terminal block position on the right which is labeled NEG is where the neutral connection is made The neutral connection at this terminal block cover is shorted with the neutral connection on J29 so the neutral only needs to be connected to one of these two positions Note that the order of the phase line and neutral is reversed here compared to the order on J29 Terminal block J29 co...

Page 30: ...e terminal block position on the most right which is labeled POS is where the positive terminal of the CT should be connected The terminal block position on the most left which is labeled NEG is where the negative terminal of the CT should be connected Select the applied current to the input of the CT so that it does not exceed 100 A In addition before performing any test verify that this terminal...

Page 31: ...puts after the sensors for line B This terminal block is a three position terminal block but only the leftmost and rightmost positions are used The center position which is connected to GND is not connected to the CT The terminal block position on the most right which is labeled POS is where the positive terminal of the CT should be connected Connect the negative terminal of the CT to the terminal...

Page 32: ...er here to bypass using the TPS70933 If a jumper is placed at J1 and another jumper is at J2 the TPS25921L input voltage and DVCC is supplied from the same source header J4 so only one external power supply is necessary If it is desired to use a separate power supply for DVCC and the TPS25921L then the jumper at J1 can be removed and the desired TPS25921L can be applied directly at pin 2 of the J1...

Page 33: ...lly output This header is not isolated from AC mains so do not connect measuring equipment here especially for the one voltage configuration If it is desired to test the reactive power pulses use the ISO_REACT pin of J18 instead since it is isolated J18 4 pin header Isolated pulses header Probe here for the isolated cumulative active energy pulses and the isolated cumulative three phase reactive e...

Page 34: ... on J29 J29 2 pin terminal block Phase B voltage WARNING Phase B line connection For the two voltage configuration this terminal block is connected to the Neutral voltage and phase B line voltage connections on the reference design case using wires For the one voltage configuration this terminal block is not used Connect the pin on the terminal block denoted by a NEG on the PCB silk screen to neut...

Page 35: ...hreshold the overvoltage threshold is also tested The overvoltage threshold test is performed by increasing the power supply voltage from 5 V to 6 V and logging at which voltage would the OUT pin of the TPS25921L device get disconnected from the IN pin After determining the overvoltage threshold the voltage is decreased back towards 5 V to determine at what voltage from the external power supply w...

Page 36: ...ation testing was specifically done for the cumulative two voltage active energy test cumulative one voltage active energy test and the individual phase active energy tests Another set of energy tests performed were frequency variation tests For this test the frequency is varied by 2 Hz from its 60 Hz nominal frequency This test is conducted at 0 5 A and 10 A at phase shifts of 0 60 and 60 The res...

Page 37: ...ignation column shows which characters correspond to which metering parameter Table 3 2 Displayed Parameters PARAMETER NAME DESIGNATION UNITS COMMENTS Active power Watt W This parameter is displayed for each phase The aggregate active power is also displayed Reactive power Volt Ampere Reactive var This parameter is displayed for each phase The aggregate reactive power is also displayed Apparent po...

Page 38: ... in RS 485 option A USB to RS 485 adapter can be used to communicate between the PC GUI and the RS 485 port on this design The USB to RS 485 adapter should create a COM port on the PC when it is plugged in The other end of the adapter should have wires for the RS 485 Data A and Data B connections as well as a GND connection and a 5 V power connection which all should be connected to the J25 screw ...

Page 39: ...sign properly the top left button is green If there are problems with connections or if the code is not configured correctly the button is red Click the green button to view the results Figure 3 11 GUI Startup Window Upon clicking on the green button the results window opens see Figure 3 12 In the figure there is a trailing L or C on the Power factor values to indicate an inductive or capacitive l...

Page 40: ...ow the user can also view the meter settings by clicking the Meter features button view the system calibration factors by clicking the Meter calibration factors button or open the window used for calibrating the system by clicking the Manual cal button Hardware Software Testing Requirements and Test Results www ti com 40 High Accuracy Split Phase CT Electricity Meter Reference Design Using Standal...

Page 41: ...alibration factors are independent of each other Therefore calibrating voltage does not affect the readings for RMS current or power When the meter SW is flashed on the MSP432 devices for the first time default calibration factors are loaded into these calibration factors These values are modified through the GUI during calibration The calibration factors are stored in INFO_MEM and therefore remai...

Page 42: ...ergy error as is done with voltage and power can be done this method is not the most accurate and should be avoided The best option to get the Correction is directly from the reference meters measurement error of the active power This error is obtained by feeding energy pulses to the reference meter To perform active power calibration complete the following steps 1 Turn off the system and connect ...

Page 43: ...om Step 3 is not close to zero or is unacceptable perform phase correction by following these steps a Enter a value as an update for the Phase Correction field for the phase that is being calibrated Usually a small integer must be entered to bring the error closer to zero Additionally for a phase shift greater than 0 for example 60 a positive negative error requires a positive negative number as c...

Page 44: ...ally done by following the active power and voltage gain calibration steps Figure 3 15 Calibration Factors Window Hardware Software Testing Requirements and Test Results www ti com 44 High Accuracy Split Phase CT Electricity Meter Reference Design Using Standalone ADCs TIDUEM8B MARCH 2019 REVISED FEBRUARY 2021 Submit Document Feedback Copyright 2021 Texas Instruments Incorporated ...

Page 45: ...04 V Based on data sheet typical value for internal UVLO threshold rising and hysteresis Release UVLO VIN Rising 4 28 V 4 26 V Based on data sheet typical value for internal UVLO threshold rising Release overvoltage condition VIN Falling 5 62 V 5 57 V Taken from TPS25921 calculation sheet and selected resistor values Overvoltage cutoff threshold VIN Rising 5 81 V 5 78 V Taken from TPS25921 calcula...

Page 46: ...y Error Versus Voltage Two Voltage Mode VOLTAGE V ERROR 240 0 0113 120 0 0067 60 0 01 30 0 012 15 0 015 Table 3 6 Phase A Active Energy Error Versus Current Two Voltage Mode CURRENT A 0 60 60 0 05 0 02 0 007 0 062 0 10 0 025 0 017 0 057 0 25 0 007 0 031 0 051 0 50 0 001 0 029 0 031 1 00 0 0075 0 034 0 021 2 00 0 0 04 0 036 5 00 0 003 0 019 0 019 10 00 0 007 0 009 0 004 20 00 0 007 0 006 0 013 30 0...

Page 47: ...7 Phase A Active Energy Error Versus Current Two Voltage Mode www ti com Hardware Software Testing Requirements and Test Results TIDUEM8B MARCH 2019 REVISED FEBRUARY 2021 Submit Document Feedback High Accuracy Split Phase CT Electricity Meter Reference Design Using Standalone ADCs 47 Copyright 2021 Texas Instruments Incorporated ...

Page 48: ...0 019 0 036 0 011 40 00 0 023 0 045 0 50 00 0 014 0 06 0 0395 60 00 0 011 0 075 0 045 70 00 0 01 0 074 0 054 80 00 0 0077 0 08 0 064 90 00 0 003 0 068 0 066 100 00 0 011 0 042 0 052 Current A Active Energy Error 0 10 20 30 40 50 60 70 80 90 100 0 5 0 4 0 3 0 2 0 1 0 0 1 0 2 0 3 0 4 0 5 D002 0 60 60 Figure 3 18 Phase B Active Energy Error Versus Current Two Voltage Mode Hardware Software Testing Re...

Page 49: ...00 0 002 0 007 0 0085 40 00 0 0 016 0 019 50 00 0 003 0 035 0 042 60 00 0 002 0 047 0 053 70 00 0 009 0 047 0 063 80 00 0 007 0 05 0 067 90 00 0 013 0 045 0 08 100 00 0 0223 0 04 0 092 Current A Active Energy Error 0 10 20 30 40 50 60 70 80 90 100 0 5 0 4 0 3 0 2 0 1 0 0 1 0 2 0 3 0 4 0 5 D003 0 60 60 Figure 3 19 Cumulative Phase Active Energy Error Versus Current Two Voltage Mode www ti com Hardw...

Page 50: ...0 0 017 0 019 0 0123 40 00 0 013 0 0225 0 01 50 00 0 031 0 058 0 001 60 00 0 023 0 06 0 012 70 00 0 0183 0 058 0 023 80 00 0 005 0 052 0 027 90 00 0 009 0 049 0 036 100 00 0 0013 0 045 0 045 Current A Active Energy Error 0 10 20 30 40 50 60 70 80 90 100 0 5 0 4 0 3 0 2 0 1 0 0 1 0 2 0 3 0 4 0 5 D004 0 60 60 Figure 3 20 Cumulative Phase Active Energy Error Versus Current One Voltage Mode Hardware S...

Page 51: ... 5 0 4 0 3 0 2 0 1 0 0 1 0 2 0 3 0 4 0 5 D005 30 60 30 60 Figure 3 21 Cumulative Reactive Energy Error Versus Current Two Voltage Mode Table 3 14 Cumulative Active Energy Measurement Error Versus Frequency 2 Hz From Nominal Frequency CONDITIONS 58 Hz 60 Hz 62 Hz 0 5 A 0 0 006 0 0017 0 007 0 5 A 60 0 058 0 032 0 032 0 5 A 300 0 045 0 032 0 032 10 A 0 0 0047 0 001 0 0033 10 A 60 0 025 0 0073 0 008 1...

Page 52: ...038 39 988 0 0395 50 00 50 0054 49 989 0 0328 60 00 60 0066 59 984 0 0377 70 00 70 0091 69 981 0 0402 80 00 80 0127 79 981 0 0396 90 00 90 018 89 976 0 0467 100 00 100 024 99 974 0 0500 Current A RMS Current Error 0 10 20 30 40 50 60 70 80 90 100 0 2 0 15 0 1 0 05 0 0 05 0 1 0 15 0 2 D006 Figure 3 22 Phase A RMS Current Error Two Voltage Mode Hardware Software Testing Requirements and Test Results...

Page 53: ...936 39 99 0 0090 50 00 49 9918 49 983 0 0176 60 00 59 9906 59 979 0 0193 70 00 69 9921 69 981 0 0159 80 00 79 9924 79 976 0 0205 90 00 89 9942 89 97 0 0269 100 00 99 9997 99 97 0 0297 Current A RMS Current Error 0 10 20 30 40 50 60 70 80 90 100 0 2 0 15 0 1 0 05 0 0 05 0 1 0 15 0 2 D007 Figure 3 23 Phase B RMS Current Error Two Voltage Mode www ti com Hardware Software Testing Requirements and Tes...

Page 54: ...00 200 049 200 0 0245 220 220 057 220 0 0259 230 230 067 230 0 0291 240 240 074 240 0 0308 260 260 087 260 02 0 0258 270 270 104 270 03 0 0274 Voltage V RMS Voltage Error 80 100 120 140 160 180 200 220 240 260 280 0 2 0 15 0 1 0 05 0 0 05 0 1 0 15 0 2 D008 Figure 3 24 Phase A RMS Voltage Error Two Voltage Mode Hardware Software Testing Requirements and Test Results www ti com 54 High Accuracy Spli...

Page 55: ...6 200 01 0 0230 220 220 069 220 01 0 0268 230 230 079 230 02 0 0256 240 250 087 250 02 0 0268 260 260 103 260 03 0 0281 270 270 114 270 03 0 0311 Voltage V RMS Voltage Error 80 100 120 140 160 180 200 220 240 260 280 0 2 0 15 0 1 0 05 0 0 05 0 1 0 15 0 2 D009 Figure 3 25 Phase B RMS Voltage Error Two Voltage Mode www ti com Hardware Software Testing Requirements and Test Results TIDUEM8B MARCH 201...

Page 56: ...02 0 075 0 076 70 0 002 0 0833 0 085 80 0 0015 0 09 0 099 90 0 003 0 096 0 109 100 0 009 0 099 0 125 Current A Error 0 10 20 30 40 50 60 70 80 90 100 1 0 8 0 6 0 4 0 2 0 0 2 0 4 0 6 0 8 1 D001 0 60 60 Figure 3 26 Active Energy Error Versus Current 32 ksps Hardware Software Testing Requirements and Test Results www ti com 56 High Accuracy Split Phase CT Electricity Meter Reference Design Using Stan...

Page 57: ...converter to another This swapped order is dealt with in this design by swapping the connection order of the wires connected to the voltage and current terminals the order of wires is reversed between J26 and J27 current terminals and it is also reversed between J28 and J29 voltage terminals Minimize the length of the traces used to connect the crystal to the microcontroller Place guard rings arou...

Page 58: ...e Grid Infrastructure group at Texas Instruments where he primarily works on grid monitoring reference design development Mekre received his bachelor of science and master of science in computer engineering from the Georgia Institute of Technology MICKAEL CHOUTEAU is a field application engineer at Texas Instruments where he is responsible for technical support for industrial customer His design e...

Page 59: ...s are subject to change without notice TI grants you permission to use these resources only for development of an application that uses the TI products described in the resource Other reproduction and display of these resources is prohibited No license is granted to any other TI intellectual property right or to any third party intellectual property right TI disclaims responsibility for and you wi...

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