UM10756 EM783 frequently asked questions (FAQ)
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1. gt measured with EM783 n 5 current inputin MIG aa anes variants 2 8 214 Up to which harmonic can EM783 measure 5 2 5 2 Does the phase of the voltage and current inputs lle eee i 9 2 2 Metrology engine software interface 5 yequire matcnng on te APE N ce oe 2 5 3 Why does the metrology engine report the active 2 2 1 Is the metrology engine software source code l 9 Nel 0 ee 5 power as a negative quantity SRA ir i 2 2 2 What are the interfaces provided by the aad Foware the unusediinputs of opamps connected creiren e a eninin EE 9 metrology engine software c ccceseeeeeees 5 255 Does the burdeniresistor reduire specific 2 2 3 How are the initial values computed for the lacement q P 9 calibration data supplied to the metrology engine p oireena sesseeeennnnaeeeennnensseecene 2 5 6 What should be the upper limit on the board software using metrology_ranges_t structure 5 ise levelt hieve the desired racy 9 2 2 4 What is the recommended value for integration NOISE EVE TO ACENG aaa COSIMO ACCUAGY f ii 2 5 7 Does the opamp feedback components require period parameter for the metrology engine m 9 initialization nener 7 Specie NAIDU riiet finetea 225 What do the following members in 3 Legal Information E A cas 10 metrology_result_t denote vphigh vplow iphigh 3 1 Definitions EARRA ATARA DARAI PA RREAN IARAA RARAN ARABAR NARRAN 1 0 HOW os ccsuctint tacesastsheciecscGthe incgetintedeagis thee2. 95 of VDD at the EM783 input this is to avoid operating in the non linear regions of the opamps Consider the following sample design for 220 V AC mains Max input voltage Vmax RMS 260 V VDD 3 3 V Maximum peak value of the input voltage 260 x V2 367 7 V 95 of VDD 0 95 x 3 3 3 135 V 367 7 V peak input AC voltage produces a signal with a peak of 3 135 V at the EM783 input Hence for a peak of 3 3 V at the EM783 input the peak value of the input voltage must be 3 3 x 367 7 3 135 387 05 V Therefore the initial value for the range parameter 2 x 387 05 774 1 V lbp This parameter represents the maximum peak to peak value of the AC current signal at the input of the AFE that produces a voltage signal with a peak to peak value of VDD at the EM783 input The value of this parameter depends on the transfer function of the AFE circuitry The high gain current channel is designed to measure the current in the range of 0 to Imax 32 Its value is at least Ipp high _ gain Imax 32 2 V2 2 In practice the circuit design ensures that the maximum peak to peak input voltage results only in a peak to peak voltage swing between 5 and 95 of VDD at the EM783 input this is to avoid operating in the non linear regions of the opamps Consider the following sample design a 220 V AC mains b Max RMS current to be measured Imax 70 A c Gain of the high gain channel 32 d VDD 3 3V Maximum peak value of the
3. All rights reserved For more information please visit http www nxp com For sales office addresses please send an email to salesaddresses nxp com Date of release 17 December 2013 Document identifier UM10756
4. UM10756 EM783 frequently asked questions FAQ Rev 1 1 17 December 2013 Document information Info Content User manual Keywords EM783 FAQ Metrology Abstract Frequently asked questions on EM783 NXP Semiconductors U M1 0756 EM783 frequently asked questions FAQ Revision history Rev Date Description 1 1 20131217 Corrected EM783 app note to EM783 SDK user manual 1 0 20131015 Initial version Contact information For more information please visit http www nxp com For sales office addresses please send an email to salesaddresses nxp com UM10756 All information provided in this document is subject to legal disclaimers NXP B V 2013 All rights reserved User manual Rev 1 1 17 December 2013 2 of 14 NXP Semiconductors U M1 0756 EM783 frequently asked questions FAQ 1 Introduction UM10756 EM783 is the next generation e metering chip with a built in metrology engine EM783 is built around a low power cost effective and industry standard ARM Cortex M0 core The ARM Cortex M0 runs with a speed up to 48 MHz and offers 4 kB of EEPROM 32 kB of flash memory 8 kB of SRAM and various serial peripherals For design flexibility NXP offers multiple variants of EM783 as single channel SC multi channel MC single phase SP and three phase TP The variant chips are e EM783 MC3 e EM783 MC6 e EM783 SC e EM783 SP e EM783 TP The EM783 reference de
5. ages incurred by customer based on reasonable reliance up to the greater of the amount actually paid by customer for the product or five dollars US 5 00 The foregoing limitations exclusions and disclaimers shall apply to the maximum extent permitted by applicable law even if any remedy fails of its essential purpose 3 3 Trademarks Notice All referenced brands product names service names and trademarks are property of their respective owners NXP B V 2013 All rights reserved User manual Rev 1 1 17 December 2013 10 of 14 NXP Semiconductors U M1 0756 EM783 frequently asked questions FAQ Notes UM10756 All information provided in this document is subject to legal disclaimers NXP B V 2013 All rights reserved User manual Rev 1 1 17 December 2013 11 of 14 NXP Semiconductors U M1 0756 EM783 frequently asked questions FAQ 4 List of figures Fig 1 EM783 block diagram eecceeeeeeeeeseeeeeeerees 3 Fig 2 Caution 22 228 eke Ae 4 UM10756 All information provided in this document is subject to legal disclaimers NXP B V 2013 All rights reserved User manual Rev 1 1 17 December 2013 12 of 14 NXP Semiconductors U M1 0756 EM783 frequently asked questions FAQ 5 List of tables Table 1 EM783 ACCUraCy eeeeeeeeeeeeeeeteeeeeeeeeteneertaees 5 Table 2 EM783 SDK toolchain list 00 0 ee 8 UM10756 All information provided in this document is
6. bration procedure corrects for the phase difference between the two signals Refer to the calibration section of the EM783 SDK user manual for more details on phase correction All information provided in this document is subject to legal disclaimers NXP B V 2013 All rights reserved User manual Rev 1 1 17 December 2013 8 of 14 NXP Semiconductors U M1 0756 UM10756 2 5 3 2 5 4 2 5 5 2 5 6 2 5 7 EM783 frequently asked questions FAQ Why does the metrology engine report the active power as a negative quantity The active power is computed as a negative quantity if 1 The CT terminal connections to the AFE are reversed 2 The direction of current flow from the source to the load through the CT is reversed How are the unused inputs of opamps connected For minimum opamp power consumption 1 Connect the positive input of the opamp to VDD 2 through a resistive divider network using two 1 MQ resistors 2 Tie the negative input of the opamp to the opamp output Does the burden resistor require specific placement Place the burden resistor as close to the opamp as possible Also ensure that the trace connecting the current transformer CT to the burden resistor is as short as possible What should be the upper limit on the board noise level to achieve the desired accuracy To meet the desired accuracy and dynamic range the PCB noise level should not exceed 10 MVpp Does the opamp feedbac
7. can measure up to 64 harmonic Metrology engine software interface Is the metrology engine software source code available No Metrology engine software for EM783 is provided only in the binary form as a library The interfaces provided by the metrology engine software and the API call sequence are detailed in EM783_API pdf The API document can be downloaded from the EM783 support website What are the interfaces provided by the metrology engine software Refer to EM783_API pdf How are the initial values computed for the calibration data supplied to the metrology engine software using metrology ranges _t structure The calibration data supplied to the metrology engine software via the metrology_ranges_t structure are 1 Vpp This parameter represents the maximum peak to peak value of the AC voltage signal at the input of the AFE that produces a voltage signal with a peak to peak value of VDD at the EM783 input The value of this parameter depends on the transfer function of the AFE circuitry Its value is at least Vpp V max 2 4 2 1 All information provided in this document is subject to legal disclaimers NXP B V 2013 All rights reserved User manual Rev 1 1 17 December 2013 5 of 14 NXP Semiconductors U M1 0756 UM10756 EM783 frequently asked questions FAQ In practice the circuit design ensures that the maximum peak to peak input voltage results only in a peak to peak voltage swing between 5 and
8. cssoatocad 7 3 2 DISCIANMOMS ciiisean onina 10 2 2 6 What is metrology_offset_t structure used for 7 3 3 Trademarks 0ccccseeseeeeeseeeseseseesseeeseseseeees 10 2 2 6 1 Howare the values computed for the offset data 4 List of TIQUPES wicsccciesscccssnsaccesensnccsessascscenssiesnanoas 12 supplied to the metrology engine software using 5 List of tables csscssssssssecessesesseeeeeseaeeeeteseeeeees 13 the metrology_set_offsets API ssssssssssssrssenrsnnnnns 7 6 COMteN Saa aa an anaa aaea Eaa aa Aaaa E iaa 14 2 2 7 What is the sampling frequency of the metrology SNOME arpa a r e EE a E 7 2 2 8 How does EM783 metrology engine select between the high gain and low gain channels 7 2 2 8 1 Are external components such as relays required for the channel selection ccsssceeeeeeeees 7 2 2 9 What is the shortest response time time at which the measurement results are available of the metrology ENGiNe eecceeceeeeeeeeeeeeeeeees 8 2 2 10 Does the accuracy of the metrology engine calibrated with 220 V 50 Hz mains remain intact when the system is used with 110 V 60 Hz nae i aE E E ySoceseshonedaatac Sezedacees recta 8 2 3 SDK for EM783 c ccceeeeceeeeeseeeeeseseeeeesneeeeees 8 2 3 1 Where can the EM783 SDK package be Please be aware that important notices concerning this document and the product s described herein have been included in the section Legal information NXP B V 2013
9. f the voltage and current signals during the last integration period These values are used in the offset calibration 1 vphigh maximum positive peak of the input voltage signal 2 vplow maximum negative peak of the input voltage signal 3 iphigh maximum positive peak of the input current signal 4 iplow maximum negative peak of the input current signal What is metrology_offset_t structure used for The data supplied by the metrology_offset_t structure are used to compensate for the opamp input offset errors How are the values computed for the offset data supplied to the metrology engine software using the metrology _set_offsets API The detailed steps to determine the value of the offsets for all the voltage and current channels are listed in the section Calibration of offsets in the EM783 SDK user manual vphigh vplow iphigh iplow members of metrology_result_t are used for the offset calibration Summary of the steps to determine the offsets is as follows 1 Supply the voltage input from an AC source to the voltage input of EM783 EVM 2 Observe the values of positive and negative voltage peaks 3 If the value of positive peak is equal to the negative peak offset value for the channel is 0 4 Ifthe value of positive and negative peak values are not equal then the offset parameter is computed as follows Offset Vphigh Vplow 2 3 5 Apply the offset and ensure that both positive and nega
10. gulations Export might require a prior authorization from competent authorities Evaluation products This product is provided on an as is and with all faults basis for evaluation purposes only NXP Semiconductors its affiliates and their suppliers expressly disclaim all warranties whether express implied or statutory including but not limited to the implied warranties of non infringement merchantability and fitness for a particular purpose The entire risk as to the quality or arising out of the use or performance of this product remains with customer In no event shall NXP Semiconductors its affiliates or their suppliers be liable to customer for any special indirect consequential punitive or incidental damages including without limitation damages for loss of business business interruption loss of use loss of data or information and the like arising out the use of or inability to use the product whether or not based on tort including negligence strict liability breach of contract breach of warranty or any other theory even if advised of the possibility of such damages Notwithstanding any damages that customer might incur for any reason whatsoever including without limitation all damages referenced above and all direct or general damages the entire liability of NXP Semiconductors its affiliates and their suppliers and customer s exclusive remedy for all of the foregoing shall be limited to actual dam
11. input current 70 32 x V2 3 09 A 95 of VDD 0 95 x 3 3 3 135 V 3 09 A peak input AC current produces a signal with a peak of 3 135 V at the EM783 input Hence for a peak of 3 3 V at the EM783 input the peak value of the input current must be 3 3 x 3 09 3 135 3 253 A Therefore the initial value for the range parameter 2 x 3 253 6 506 A The low gain current channel is designed to measure a maximum current Of imax Hence the initial value of the calibration parameter for the low gain channel is 32 x 6 506 208 192 A Delta Phi This parameter represents the phase angle error between the voltage and the current signals for a channel with a pure resistive load The initial value of this parameter is set to 0 All information provided in this document is subject to legal disclaimers NXP B V 2013 All rights reserved User manual Rev 1 1 17 December 2013 6 of 14 NXP Semiconductors U M1 0756 UM10756 2 2 4 2 2 5 2 2 6 2 2 6 1 2 2 7 2 2 8 2 2 8 1 EM783 frequently asked questions FAQ What is the recommended value for integration period parameter for the metrology engine initialization The recommended value of integration period parameter for the metrology engine is between 45 and 130 mains periods inclusive What do the following members in metrology_result_t denote vphigh vplow iphigh iplow These fields indicate the maximum positive and negative peak values o
12. k components require specific placement Place the opamp feedback components as close to the opamps as possible All information provided in this document is subject to legal disclaimers NXP B V 2013 All rights reserved User manual Rev 1 1 17 December 2013 9 of 14 NXP Semiconductors UM10756 3 Legal information EM783 frequently asked questions FAQ 3 1 Definitions Draft The document is a draft version only The content is still under internal review and subject to formal approval which may result in modifications or additions NXP Semiconductors does not give any representations or warranties as to the accuracy or completeness of information included herein and shall have no liability for the consequences of use of such information 3 2 Disclaimers Limited warranty and liability Information in this document is believed to be accurate and reliable However NXP Semiconductors does not give any representations or warranties expressed or implied as to the accuracy or completeness of such information and shall have no liability for the consequences of use of such information In no event shall NXP Semiconductors be liable for any indirect incidental punitive special or consequential damages including without limitation lost profits lost savings business interruption costs related to the removal or replacement of any products or rework charges whether or not such damages are based on tor
13. s will be suitable for the specified use without further testing or modification Customers are responsible for the design and operation of their applications and products using NXP Semiconductors products and NXP Semiconductors accepts no liability for any assistance with applications or customer product design It is customer s sole responsibility to determine UM10756 All information provided in this document is subject to legal disclaimers whether the NXP Semiconductors product is suitable and fit for the customer s applications and products planned as well as for the planned application and use of customer s third party customer s Customers should provide appropriate design and operating safeguards to minimize the risks associated with their applications and products NXP Semiconductors does not accept any liability related to any default damage costs or problem which is based on any weakness or default in the customer s applications or products or the application or use by customer s third party customer s Customer is responsible for doing all necessary testing for the customer s applications and products using NXP Semiconductors products in order to avoid a default of the applications and the products or of the application or use by customer s third party customer s NXP does not accept any liability in this respect Export control This document as well as the item s described herein may be subject to export control re
14. sign evaluation module EVM includes an SDK package consisting of a reference energy meter application and metrology library in binary format The metrology library provides the interface to the EM783 metrology engine The SDK package is available for download from the NXP website This document provides details on using EM783 in question and answer format 1 1 Key applications e Smart plugs and plug meters e Single phase residential meters e DALI DMX and KNX nodes with metering functionality e Industrial sub meters e Power monitors for servers e Smart appliances 1 2 Block diagram Cortex MO 4kB 50 MHz EEPROM Metrology Engine with Net 8kB 32 kB Frequency SRAM Flash Tracking Advanced Peripheral Bus Temperature t t Sensor 1x SPI 1 x UART 1x l c RS485 IrDA aaa 009758 Fig 1 EM783 block diagram All information provided in this document is subject to legal disclaimers NXP B V 2013 All rights reserved User manual Rev 1 1 17 December 2013 3 of 14 NXP Semiconductors U M1 0756 EM783 frequently asked questions FAQ 1 3 Disclaimer The EM783 EVM is a prototype only for demonstration and evaluation purposes Improper use of the EVM can result in electrical shock and fire hazard due to the operational voltages and currents of the EVM Ensure that only qualified personnel familiar with the risks and hazards associated with high voltages and currents handle the EVM Do not
15. subject to legal disclaimers NXP B V 2013 All rights reserved User manual Rev 1 1 17 December 2013 13 of 14 NXP Semiconductors UM10756 EM783 frequently asked questions FAQ 6 Contents 1 INtFOGUCTION wissssccesscccissccis cas saniat eanan niidina araa 3 downloaded from ccccscccecssseeeeeeseeeeesneeeeees 8 1 1 Key Applications c cccccscscscesesesesesesceteteesesesees 3 2 3 2 What toolchains and debuggers does the EM783 1 2 Block diagram ne ee ee ne eee 3 SDK SUpport sssssscsssssssssssenssesensseseneseseessens 8 1 3 DiSCIAIMEL cecccccccccccccccccccccceccceccccececcceeecececeseetees 4 2 4 Calibration oo eee eeeeee esses eeeeeseeeeeteneneeeeees 8 1 4 Support information c lt ccecascaconcescasancercasonceneseneees 4 241 What is the procedure used to calibrate the 2 EM783 frequently asked questionS 5 metrology engine diadelieeavaueiedede ete o 8 21 EM783 specification 5 2 4 2 Does the metrology firmware require upgrading 21 1 What is the accuracy of EM783 ere aaa 2 5 when the analog front end components are 1 Os EE T fet Nay 212 What is the accuracy of the frequency modified soeeeneeenneeneeeneconeceneeoneconecanecaneteneeanetanetenss 8 PETA DEE TIG TIED css ac Seeds ccc ease cceccachosesicect 5 2 5 Analog front end GeSIQN cccccecceeeeeeeeeeeeeeee 8 ore 2 5 1 Why are two gain channels used for a single 2 1 3 What is the range of current that can be i f
16. t including negligence warranty breach of contract or any other legal theory Notwithstanding any damages that customer might incur for any reason whatsoever NXP Semiconductors aggregate and cumulative liability towards customer for the products described herein shall be limited in accordance with the Terms and conditions of commercial sale of NXP Semiconductors Right to make changes NXP Semiconductors reserves the right to make changes to information published in this document including without limitation specifications and product descriptions at any time and without notice This document supersedes and replaces all information supplied prior to the publication hereof Suitability for use NXP Semiconductors products are not designed authorized or warranted to be suitable for use in life support life critical or safety critical systems or equipment nor in applications where failure or malfunction of an NXP Semiconductors product can reasonably be expected to result in personal injury death or severe property or environmental damage NXP Semiconductors accepts no liability for inclusion and or use of NXP Semiconductors products in such equipment or applications and therefore such inclusion and or use is at the customer s own risk Applications Applications that are described herein for any of these products are for illustrative purposes only NXP Semiconductors makes no representation or warranty that such application
17. tive peaks have the same value What is the sampling frequency of the metrology engine Metrology engine samples at 6 4 ksps How does EM783 metrology engine select between the high gain and low gain channels EM783 metrology engine samples both the high gain and low gain channels simultaneously and combines the data to generate the metrology results for the current input Are external components such as relays required for the channel selection No external hardware components are required on the board to select between the high gain and low gain channels All information provided in this document is subject to legal disclaimers NXP B V 2013 All rights reserved User manual Rev 1 1 17 December 2013 7 of 14 NXP Semiconductors U M1 0756 UM10756 2 2 9 2 2 10 2 3 2 3 1 2 3 2 2 4 2 4 1 2 4 2 2 5 2 5 1 2 5 2 EM783 frequently asked questions FAQ What is the shortest response time time at which the measurement results are available of the metrology engine The metrology engine integration duration is configurable from 45 to 130 mains periods The metrology result is available only at the end of every integration period Hence the integration period is the shortest response time of the metrology engine For example For 220 V 50 Hz mains system with integration period configured to 130 mains periods the metrology results will be available every 2 6 s 130 1 50 Does the acc
18. touch the EVM or its components when the EVM is energized Fig 2 Caution 1 4 Support information Use the following link for additional information on EM783 http Awww nxp com products power_management energy measurement ics series EM7 83 html Send an email to em7xx support nxp com for technical support on EM783 UM10756 All information provided in this document is subject to legal disclaimers NXP B V 2013 All rights reserved User manual Rev 1 1 17 December 2013 4 of 14 NXP Semiconductors U M1 0756 EM783 frequently asked questions FAQ 2 EM783 frequently asked questions UM10756 2 1 2 1 1 2 2 2 2 1 2 2 2 2 2 3 EM783 specification What is the accuracy of EM783 The table below lists the accuracy of the energy measurements provided by the different variants of the EM783 Table 1 EM783 Accuracy Variant Accuracy Dynamic range MC3 1 1000 SC 1 1000 SP 1 1000 MC6 2 50 TP 2 50 What is the accuracy of the frequency measurement 0 01 is the accuracy of frequency measurement What is the range of current that can be measured with EM783 The analog front end design AFE determines the range of current that can be measured using EM783 The AFE scales the input voltage and current signals to a voltage signal in the range from VSS to VDD at EM783 inputs EM783 samples this signal and provides the metrology data Up to which harmonic can EM783 measure EM783
19. uracy of the metrology engine calibrated with 220 V 50 Hz mains remain intact when the system is used with 110 V 60 Hz mains No The unit needs recalibration with 110 V 60 Hz mains input to achieve the desired accuracy SDK for EM783 Where can the EM783 SDK package be downloaded from EM783 SDK package can be downloaded from the EM783 support website What toolchains and debuggers does the EM783 SDK support EM783 1 0 EVM is tested with the following toolchain debugger combinations Table 2 EM783 SDK toolchain list Toolchain Debugger Keil uVision 4 60 0 0 ULINK2 Calibration What is the procedure used to calibrate the metrology engine Refer to the calibration section of the EM783 SDK user manual available at the EM783 support website Does the metrology firmware require upgrading when the analog front end components are modified No The metrology firmware need not be upgraded if the analog frontend is re designed for a different current range The unit requires only recalibration Analog front end design Why are two gain channels used for a single current input in MC3 SC and SP variants MC3 SC and SP variants of EM783 use two gain channels for a single current input to achieve the accuracy and the dynamic range listed in Table 1 Does the phase of the voltage and current inputs require matching on the AFE No The voltage and the current signal phases need not be matched by the AFE circuitry Instead the cali
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