Reduced cost automatic meter reading system and method using locally communicating utility meters

• US 7,548,223 B2
• Filed: 08/06/2004
• Issued: 06/16/2009
• Est. Priority Date: 08/15/1997
• Status: Expired due to Term

• Current Assignee: Aclara Meters LLC (Hubbell, Inc.)
• Original Assignee: General Electric Company
• Inventors: Berkcan, Ertugrul, Staver, Daniel Arthur, Harrison, Daniel David, Daum, Wolfgang, Hoctor, Ralph Thomas, Welles, Kenneth Brakeley II, Brooksby, Glen William
• Primary Examiner(s): Hjerpe; Richard
• Assistant Examiner(s): NGUYEN, KIMNHUNG T
• Application Number:
  US10/913,100
• Publication Number:
  US 20050024234A1
• Time in Patent Office: 1,775 Days
• Field of Search: 345/87, 340/870.1, 361/667
• US Class Current: 345/87
• CPC Class Codes: G01D 4/004 Remote reading of utility meters to a fixed location
• CPC Class Codes: G01R 21/133 by using digital technique
• CPC Class Codes: G01R 22/00 Arrangements for measuring time integral of electric power or current, e.g. electricity meters
• CPC Class Codes: H04Q 2209/30 using a wired architecture
• CPC Class Codes: H04Q 2209/43 using wireless personal area networks [WPAN], e.g. 802.15, 802.15.1, 802.15.4, Bluetooth or ZigBee
• CPC Class Codes: H04Q 2209/60 for transmitting utility meters data, i.e. transmission of data from the reader of the utility meter
• CPC Class Codes: H04Q 2209/823 where the data is sent when the measured values exceed a threshold, e.g. sending an alarm
• CPC Class Codes: H04Q 9/00 Arrangements in telecontrol or telemetry systems for selectively calling a substation from a main station, in which substation desired apparatus is selected for applying a control signal thereto or for obtaining measured values therefrom
• CPC Class Codes: Y02B 90/20 Smart grids as enabling technology in buildings sector smart grids supporting the management or operation of end-user stationary applications in general, or like technologies with no associated climate change mitigation effect Y04S20/00
• CPC Class Codes: Y04S 20/30 Smart metering, e.g. specially adapted for remote reading

Abstract

A low cost and easy to assemble communicating utility meter provides selectable measurement, calibration, display, and communications means so as to be re-configurable based on several factors including; harmonic content of the power signal measured, LCD display alternatives, time of use measurements, bandpass filter settings, power quality measurements, PLC communications. alternatives, radio frequency communications alternatives, optical communications alternatives, and hard wire communications alternatives.

Claims

1. A circuit for filtering a current sensor signal comprising a second order infinite impulse response (IIR) filter, said IIR filter having a z domain response defined by:

$H<br><br>\left(z\right)=\frac{c<br><br>\left(z^2-1\right)}{z^2-2<br><br>k+{\hat{k}}^2},$

wherein c is a normalization constant, and wherein k is approximately equal to 1, and wherein {circumflex over (k)} is approximately equal to k.

2. The circuit as recited in claim 1, wherein said IIR filter comprises:

a first digital summer;

a unity gain amplifier coupled to said first digital summer;

a normalization constant amplifier coupled to said unity gain amplifier;

a negative unity gain amplifier coupled to said first summer and coupled to said normalization constant amplifier;

a first unit delay coupled to said unity gain amplifier;

a second unit delay coupled to said first unit delay and coupled to said negative unity gain amplifier;

a second summer coupled to said first summer;

a third unit delay coupled to said second summer;

a fourth unit delay coupled to said third unit delay;

a 2k gain amplifier coupled to said fourth unit delay and coupled to said third unit delay;

a third summer coupled to said 2k gain amplifier, and coupled to said second summer; and

a {circumflex over (k)}² gain amplifier coupled to said third summer and coupled to said fourth unit delay.

3. A method of selecting IIR filter constants k and {circumflex over (k)} within a circuit for filtering a current sensor signal, said method comprising the steps of:

selecting a first zero at z=1;

selecting a second zero at z=−

1; and

selecting a pair of poles at the roots of equation z²−

2k+{circumflex over (k)}² sufficiently close to said first zero such that said pair of poles and said first zero appear as a single pole at z=1 for frequencies within a selected pass band.

4. The method of selecting IIR filter constants, as recited in claim 3 wherein k is selected based on the equation k=1−

2<sup>−

n</sup>, wherein n is greater than 7.

5. The method of selecting IIR filter constants, as recited in claim 4 wherein i² is selected based on the equation {circumflex over (k)}²=1−

2<sup>−

(n−

)</sup>.