Method and system for sensing removal of a utility meter from its socket

• US 5,293,115 A
• Filed: 06/17/1993
• Issued: 03/08/1994
• Est. Priority Date: 08/06/1991
• Status: Expired due to Term

• Current Assignee: Itron, Inc.
• Original Assignee: Schlumberger Industries Incorporated (Schlumberger NV)
• Inventors: Swanson, Scott C.
• Primary Examiner(s): NGUYEN, VINH P
• Application Number:
  US08/077,258
• Time in Patent Office: 264 Days
• Field of Search: 324/96, 324/110, 324/156, 324/157, 340/637, 340/568, 340/571, 340/524, 340/541, 361/372
• US Class Current: 324/110
• CPC Class Codes: G01R 22/066 Arrangements for avoiding or indicating fraudulent use
• CPC Class Codes: G08B 13/1409 for removal detection of electrical appliances by detecting their physical disconnection from an electrical system, e.g. using a switch incorporated in the plug connector

Abstract

A method and system is disclosed for indication and prevention of tampering with an electricity meter having control circuitry for automatic remote reading. The control circuitry, provided externally of the meter in a base or base extension, to which the meter is connected, is also used for tamper detection. Embodiments of the invention include use of optical sensing, voltage detection and proximity detection. Ambient light sensing may be performed to detect separation of the meter from the external receptacle. Reflected light to a reflective surface of the meter is sensed to determine if the meter is properly engaged. Presence of a meter connection plug element may be sensed either optically or by position responsive switch. Voltage of the utility supply and meter user output may be monitored to determine tampering.

Claims

1. A method for ascertaining tampering of a connection between an electricity meter, of the type which includes plug extensions which plug into respective sockets in a base external to said meter, and an external base to which said electricity meter is connected and through which external power is supplied to said meter comprising the steps of:

(a) emitting light pulses from said external base;

(b) sensing light reflected by said meter by circuitry solely within said external base;

(c) generating a bilevel voltage by said circuitry within said external base, each level corresponding respectively to a relatively bright light condition and a relatively dark condition; and

(d) detecting a meter tampering condition in response to said bilevel voltage.

2. A device for detecting tampering of a connection between an electricity meter, of the type which includes plug extensions which plug into respective sockets in a base external to said meter, and an external base to which said electricity meter is plugged and through which external power is supplied to said meter, said device comprising:

(a) passive means which is part of said meter which can modify a signal from a source external to said meter;

(b) active means, contained solely within said external base, said active means not being a part of said meter or needing any physical connection to said meter apart from plugging said meter into said external base, said active means providing a signal to said passive means; and

(c) detecting means, contained solely within said external base for indicating the proximity of said meter to said external base and for thereby detecting that said meter has been unplugged from said external base, whereby a tampering condition will be indicated.

3. The device of claim 2 for detecting tampering of a connection between an electricity meter, of the type which includes plug extensions which plug into respective sockets in a base external to said meter, and an external base through which external power is supplied to said meter, wherein:

(a) said passive means includes an optically reflective portion on the rear of said meter;

(b) said active means comprises light emitting means contained solely within said external base, said active means being capable of emitting light pulses, said light pulses reflecting rom said optically reflective portion on the rear of said meter when said meter is plugged into said external base; and

(c) said detecting means comprising sensing means for sensing light reflected from said optically reflective portion on the rear of said meter and for generating a bilevel voltage, each level corresponding respectively to a relatively bright light condition and a relatively dark condition, in response to said sensing means, whereby a tampering condition of the type in which said meter is removed from said base will be indicated by the absence of reflection of light from said optically reflective portion of said meter.

4. The device of claim 3, wherein said meter is enclosed in a housing including a back plate, said back plate having a surface at least a portion of which is optically reflective;

(a) said light emitting means comprises a light emitting diode;

(b) said sensing means comprises a phototransistor positioned in a light path including said light emitting diode and the optically reflective portion of the meter back plate.

5. The device of claim 4, wherein said detecting means comprises a microprocessor including an output terminal for supplying driving pulses to said light emitting diode and an input terminal for receiving said bilevel voltage.

6. The device of claim 5, wherein said detecting means comprises circuit means responsive to a dark condition sensing output of said phototransistor to produce a tamper indicating signal during periods of light emitting diode emission and responsive to a light condition sensing output of said phototransistor during periods of non light emitting diode emission.

7. The device of claim 3 wherein said optically reflective portion comprises the meter hanger which is on the rear of a standard electricity meter.