COMMERCIAL FEATURE Kinetis M-Series as a Single Platform Solution Freescale® Semiconductor, Inc. introduces three types of metering reference designs based on the new Kinetis® M-Series Microcontrollers (MCUs). These MCUs address high accuracy and low-cost needs by providing a high performance 24-bit analog front-end combined with an embedded programmable gain amplifier (PGA) to increase the accuracy of energy measurement. These power meter reference designs were developed to demonstrate the key strengths of the Kinetis M-Series MCUs in a typical automated meter reading (AMR) applications. For measurement in three-phase installations we can offer three- phase power meter reference design (EN50470-3, class C) with in- built current transformers for current measurement up to 120 Amps. The complete signal sampling process is based on the combination of three or four 24-bit sigma-delta (SD) ADCs and one 16-bit successive approximation (SAR) ADC with an input multiplexer. As the voltage dynamic range is much smaller than the current dynamic range, we can use the high-resolution SAR converter only for voltage measurement and the SD ADC with a wide dynamic range for a current measurement. The reference designs are very suitable for real customer metering applications, thanks to their integrated human-machine interfaces (HMI) and communication interfaces for remote data collection and automated meter reading (AMR). For a faster time to market, the designs provide both the hardware and the software sources for customer applications. The described reference designs support two different types of advanced metering algorithms. Both these algorithms calculate all the billing (energies) and non-billing (U rms , I rms , etc.) metering quantities, one in the time domain and the second in the frequency domain. Both algorithms require instantaneous voltage and current samples to be provided at constant sampling intervals. For a time domain signal analysis we use a Filter-Based metering algorithm. For signal analysis in the frequency domain we use a computing technique based on the Fast Fourier Transform. The metering engine of each particular reference design contains the majority of the components for metering, communications, and backup storage together with the switch mode power supply (SMPS) which is used for supplying the meter itself. At the heart of the metering engine lies an ARM Cortex TM -M0+ core with a high performance analog front-end. The reference designs also contain a built-in optical read-out port (infrared) for a hand-held terminal reader, and an expansion header for an RF communication daughter card supporting an IEEE 802.15.4 compliant radio with ZigBee ® and/or 6LowPAN stacks (due to HAN/NAN communication). The backup battery in the meter is used to power the meter electronics in the case of power loss. Some reference designs also support electronic tamper detection circuits. The first tamper event may be generated by the Xtrinsic TM 3-axis low-power tilt sensor which may be used for cover opening detection. The second tamper event may be generated by the Xtrinsic 3-axis low-power magnetometer, which measures magnetic fields in three dimensions and is primarily used for tamper detection of the current transformers by an external strong magnet. These power meters are used for the measurement and registration of active and reactive energy with direct connections for residential metering. The metering engine of each particular meter is housed in a professional power meter enclosure according to the relevant standard. Thanks to an efficient processor core with support for 32-bit math, this enables fast execution of both metering algorithms for these reference designs. A typical active energy error of the ANSI two- phase reference design is shown in Figure 1. The error curves are very low with good margins to the specification thanks to the MCU with a high performance integrated AFE. To learn more about Kinetis microcontrollers or these reference designs, visit www.freescale.com/kinetis and www.freescale.com/ smartenergy. MI The single-phase power meter reference design is used for measurement in single-phase two-wire installations. The design is targeted specifically at the Figure 1- Typical Active Energy Error of the Kinetis M-Series Power Meter EMEA region (EN50470-3, class C). There is a cost- effective shunt resistor sensing circuit implementation used for current measurement up to 120 Amps. The two-phase power meter reference design is used for measurement in single-phase three-wire (two-phase) installations. The design is targeted specifically at the U.S. region (ANSI C12.20- 2002, class 0.2). The meter is housed in a round plastic enclosure according to the ANSI standard, with integrated power connectors for a 12S configuration and with two in-built current transformers for current measurement up to 200 Amps. METERING INTERNATIONAL ISSUE - 4 | 2013 ABOUT THE AUTHOR: Luděk Šlosarčík received his M.Sc. degree in electrical engineering from the VSB-Technical University of Ostrava in 1992 and 1997. Since 2008, he has been employeed by Freescale Semicondutor, Czech System Centre (Roznov pR), as a Systems Application Engineer with a focus in sensor and metering applications. ABOUT THE COMPANY: Freescale is the global leader in embedded processing solutions, advancing the automotive, consumer, industrial and networking markets. 45