Email

How to design 1-phase shunt electricity meters using standalone metrology ADCs

As processing requirements for electricity meters gradually increase, it becomes increasingly difficult to find one device that meets both the processing requirements for adding advanced metrology features to smart meters while also accurately sensing metrology parameters, such as RMS voltage, RMS current and active power.  To deal with this design challenge, one option is to use a separate metrology microcontroller and a standalone ADC. This session will focus on how to design electricity meters using the ADS131M04 standalone delta-sigma metrology ADCs.  The TIDA-010036 reference design with its onboard MSP432 ARM Cortex M4F metrology microcontroller will be used to illustrate how to use the ADS131M04 standalone ADC to implement a Class 0.5 single-phase meter with shunt current sensor.

Another design challenge for electricity meters is protecting meters against tampering.  One form of tampering is magnetic tampering, which is one of the most common ways to tamper with a meter. In the TIDA-010036 design, this design challenge is addressed by using a shunt current sensor as the primary current sensor and a cap-drop supply as the design’s AC/DC power supply.  Conventional cap-drop supplies have a limited maximum current; however, in this design, the switch-cap stage of the TPS7A78 enables us to get a higher maximum current output compared to conventional cap-drop supplies.  The switch-cap stage does not use magnetic components, which enables the AC/DC power supply to be magnetically immune.  Another method to tamper with the meter is to remove the neutral.  The ADS131M04 in this design uses a special current detection mode for determining this neutral current disconnection in a low-power manner so that the backup power supply lifetime is maximized.  The design also measures both the line and neutral current in case someone tries to tamper with the meter by bypassing the sensed current on one of these two channels.

1. Current sensor and metrology architecture options

This section compares two types of current sensors used in electricity meters: current transformers and shunts.  In addition, it discusses three different architectures for sensing the voltage and current samples used to calculate the metrology parameters.  These architectures include a SoC-based architecture, AFE-based architecture, and ADC-based architecture.
# Title Duration
1.1 How to design 1-phase shunt electricity meters using standalone metrology ADCs: Electricity meter current sensing options: current transformers and shunts
This module provides details on the characteristics of shunts and current transformers.
14:31
1.2 How to design 1-phase shunt electricity meters using standalone metrology ADCs: Metrology architecture options: SoCs, AFEs, and standalone ADCs
This module discusses three different architectures for sensing the voltage and current samples used to calculate the metrology parameters.
08:46
Login required

2. Introduction to TIDA-010036 reference design

This section provide an overview of the TIDA-010036 reference design, which uses the ADS131M04 delta sigma standalone ADC for sensing the voltage and current necessary to calculate metrology parameters.  The TIDA-010036 design targets Class 0.5 single-phase two-wire meters with shunt current sensors and has a compact, magnetically immune cap-drop power supply to power the design from AC mains.
# Title Duration
2.1 How to design 1-phase shunt electricity meters using standalone metrology ADCs: ADS131M04 and MSP432 features for TIDA-010036
This module discusses the features of the ADS131M04 standalone ADC and MSP432 metrology/host microcontroller in the TIDA-010036 reference design.
03:56
2.2 How to design 1-phase shunt electricity meters using standalone metrology ADCs: TIDA-010036 overview
This module provides an overview of the TIDA-010036 reference design.
08:24
Login required

3. TIDA-010036 hardware design

This section provides an overview of the hardware used in the TIDA-010036 design, which includes the circuits used to translate the Mains voltage and current to the voltage waveform sensed by the ADS131M04.  In addition, it covers the TPS7A78-based cap-drop power supply used in this design.
# Title Duration
3.1 How to design 1-phase shunt electricity meters using standalone metrology ADCs: Designing voltage and current sensing circuitry
This module discusses the circuits used in the TIDA-010036 reference design to translate Mains voltage and current to the voltage waveform fed to the ...
09:05
3.2 How to design 1-phase shunt electricity meters using standalone metrology ADCs: Using the TPS7A78 to implement a compact, magnetically immune cap-drop supply
This module discusses the advantages of using a TPS7A78 AC voltage regular for implementing a cap-drop power supply.
06:44
Login required

4. Designing software for 1-phase electricity meters that use standalone ADCs

This section covers the initialization code and algorithms that can be used to calculate metrology parameters in a single phase system using the sensed voltage and current samples.
# Title Duration
4.1 How to design 1-phase shunt electricity meters using standalone metrology ADCs: Procedure for obtaining and verifying ADC samples
This module discusses a procedure for initializing the ADS131M04, obtaining samples from the device, and calculating the CRC for checking packet integ...
12:16
4.2 How to design 1-phase shunt electricity meters using standalone metrology ADCs: Algorithms for performing metrology parameter calculations
This module discusses algorithms that can be used to calculate metrology parameters from the ADS131M04’s sensed voltage and current samples.
12:03
Login required

5. ADS131M04 current detection mode for detecting neutral removal tampering

This section discusses current detection mode, which is a special low-power mode of the ADS131M04 standalone ADC, that can detect the presence of current when someone has tampered with a meter by removing its neutral connection.
# Title Duration
5.1 How to design 1-phase shunt electricity meters using standalone metrology ADCs: Current detection mode overview
This module provides an overview of the ADS131M04’s current detection mode for detecting the removal of the neutral connection from a meter.
14:27
5.2 How to design 1-phase shunt electricity meters using standalone metrology ADCs: Current detection mode current consumption results
This module shows the current consumption results of the ADS131M04’s current detection mode.
05:52
Login required

6. Calibration and metrology accuracy results

This section discusses the procedure used to calibrate the TIDA-010037 design and the results obtained with this design.
# Title Duration
6.1 How to design 1-phase shunt electricity meters using standalone metrology ADCs: Calibration overview
This module provides an overview of a procedure that can be used to calibrate a meter that has the ADS131M04.
04:35
6.2 How to design 1-phase shunt electricity meters using standalone metrology ADCs: TIDA-010036 metrology accuracy results
This module shows the active and reactive energy error results that were obtained with the TIDA-010036 shunt-based reference design.
03:35
Login required

7. Summary

In this section, a summary of the entire “How to design 1-phase shunt electricity meters using standalone metrology ADCs” training module would be covered.  Links will be provided for the reference designs that were discussed during this training series.
# Title Duration
7.1 How to design 1-phase shunt electricity meters using standalone metrology ADCs: Summary
In this module, a summary of the entire “How to design 1-phase shunt electricity meters using standalone metrology ADCs” training series would be covered....
02:07
Login required
arrow-topclosedeletedownloadmenusearchsortingArrowszoom-inzoom-out arrow-downarrow-uparrowCircle-leftarrowCircle-rightblockDiagramcalculatorcalendarchatBubble-doublechatBubble-personchatBubble-singlecheckmark-circlechevron-downchevron-leftchevron-rightchevron-upchipclipboardclose-circlecrossReferencedashdocument-genericdocument-pdfAcrobatdocument-webevaluationModuleglobehistoryClockinfo-circlelistlockmailmyTIonlineDataSheetpersonphonequestion-circlereferenceDesignshoppingCartstartoolsvideoswarningwiki