E-Metering

In order to calculate Energy we have to collect the current and voltage information. Voltage can be known directly however current have to be measured. There are different measurement techniques as follow; Low resistance serial connection Current transformers Hall effect sensor Rogowski inductor
Analog Power Measurement
	Today power measurement is done by digital methods. In these case first of all current and voltage have to be converted from analog to digital. Therefore analog to digital converters have to be used. Digital Power Measurement Best solution for ADC is to use high SNR ratio sigma-delta converters. Solutions have to be pass from LPF in order to find active power.

Standart automatic reading electric-meter Automatic reading electric-meter with	DSP

E’METERING SOLUTION

Special circuit for STPM1x Active Power measurement application

The STPM01 is able to perform active, reactive and apparent energy measurements.
Instantaneous values for voltage and current, line frequency information.

Less than 0.1% error
Supported sensors: Rogowski, current transformer, Shunt
DSP unit: calculates the active energy.
Flexibility: 56 configuration bit can be temporary or permanently set.
SPI interface for writing and reading data, pulse output, step motor driver.
Live and neutral monitoring for tamper detection.

http://www.st.com/stonline/products/literature/ds/10853.htm

Over view

www.st.com/metering
www.stmcu.com
http://www.st.com/stonline/products/literature/ds/9324.htm
http://www.st.com/stonline/products/literature/ds/7313.htm
http://www.st.com/stonline/products/literature/an/9475.htm
http://www.st.com/stonline/products/literature/ds/8951.htm
http://www.st.com/stonline/products/families/memories/ eeprom/index.htm

STPM01

The STPM01 is designed for effective measurement of active, reactive and apparent energy in a power line system using Rogowski Coil, Current Transformer and Shunt sensors. This device can be implemented as a single chip 1-phase energy meter or as a peripheral measurement in a microcontroller based 1-phase or 3-phase energy meter. The STPM01 consists, essentially, of two parts: the analog part and the digital part. The former, is composed by preamplifier and 1st order A/D converter blocks, Band gap voltage reference, Low drop voltage regulator, the latter, is composed by system control, oscillator, hard wired DSP and SPI interface.

56-bit OTP block, There is also an OTP block, which is controlled through the SPI by means of a dedicated command set.

Measurement Requirements

Decrease the tamper ratio.
10 year life time without power
Clock accuracy: 5ppm @25C
Saving critical values on power cuts.
With optimum cost it’ s easy to convert applications to industrial standards
Suitable for harsh environment
Multi tariff

http://mcu.st.com/devicedocs-ST7LITE29F2-15.html

ST Solutions

ST7FLite2x low cost microprocessor

Tamper detection and time seal even though power failures.
Ultra low RTC current and sleep mode (small battery can be used)
Software calibration
Integrated Switch Over and PFI/PFO
Embedded crystal
Totally sealed Snap Hat cover
Alarm

Suggested ST Products: STPMxx, ST7, uPSD, STR7, STLite2x, M41(S)Txx, ST7SCR, ST80x4, M95xx, M24xx, ST485xx, ST7538, ST7540, ST202, ST232x

16-bit RISC Ultra-Low-Power Microcontroller for Electronic Flow Meters

MSP430FW423 (8KB Flash, 256B RAM)
MSP430FW425 (16KB Flash, 512B RAM)
MSP430FW427 (32KB Flash, 1024B RAM)

LC-Sensor Measurement Principal

A resonant LC circuit is used as the sensor
Electronics stimulate the resonant circuitry
This causes a damped oscillation
Damping of the oscillation depends on the location of the coil above the plate
Rotation detection is possible by monitoring the coil oscillations

Measurement Principle:

Excitation of the Resonant LC-Sensor

Measurement of the Damping Ratio

Processing the Measurement Results

The excitation is realized by applying a ‘L’ level to the resonant circuitry

The current is limited by the series resistor Rlim

After excitation, the LC circuit is allowed to oscillate (switching pin to “Hi-Z”)

Oscillations are clipped on-chip providing a defined amplitude

The 10-bit DAC defines the threshold Vref

During a defined time t gate , the comparator output is checked

Pulses can be seen if the coil is not above metal. If no pulses are present, the coil is located above metal.

The position of the coil is converted into a digital signal.

http://focus.ti.com/mcu/docs/mcuprodoverview.tsp?sectionId=95&tabId=140&familyId=342

16-bit Ultra-Low-Power Microcontroller for Energy Meters MSP430FE423 (8KB Flash, 256B RAM) MSP430FE425 (16KB Flash, 512B RAM) MSP430FE427 (32KB Flash, 1024B RAM)
Mixed-signal SOC, 5/1 chip reduction Good cost/performance ratio Low power 3V supply