Optical sensor system and method for monitoring consumables

• US 6,271,523 B1
• Filed: 03/07/2000
• Issued: 08/07/2001
• Est. Priority Date: 12/05/1997
• Status: Expired due to Fees

• Current Assignee: Precursive Wave Technologies Corporation
• Original Assignee: Precursive Wave Technologies Corporation
• Inventors: Weaver, John D., Moman, Gary
• Primary Examiner(s): Hannaher, Constantine
• Assistant Examiner(s): Israel, Andrew
• Application Number:
  US09/520,708
• Time in Patent Office: 518 Days
• Field of Search: 250/341.8, 250/349, 250/221, 250/577, 250/230, 250/231.13
• US Class Current: 250/341.8
• CPC Class Codes: G01D 4/002 Remote reading of utility meters
• CPC Class Codes: G01D 4/008 Modifications to installed utility meters to enable remote reading
• CPC Class Codes: G01D 5/40 specially adapted for use with infrared light mechanical adjustment G01D5/264
• 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

An optical sensor for monitoring a utility meter having a sweep hand indicator that moves over a meter surface of the utility meter. The optical sensor has a single infrared light emitter and two photo diodes detectors. The infrared light emitter is positioned at an angle with respect the meter surface and the sweep hand indicator of the utility meter so that the sweep hand indicator is illuminated from an angle to provide a shadow of the sweep hand indicator. The photo detectors detect changes in the intensity of light reflected on the sweep hand indicator and the background surface as well as the shadow of the sweep hand indicator. The two photo diode detectors are electrically coupled in series but in opposite directions relative to an output node, so as to cancel each other at the output node in normal operation. The passing of the sweep hand indicator changes the signal produced of each of the photo diode detectors at the output node, independently but in opposite directions.

Claims

1. A method of sensing motion of a sweep hand indicator of a meter which moves adjacent a background surface, the method comprising the steps of:

illuminating the background surface and the sweep hand indicator by an illumination source;

detecting illumination levels at two separated areas on the background surface by two detectors; and

forming a shadow under the sweep hand indicator upon illuminating the background surface and the sweep hand indicator;

wherein said step of detecting illumination levels comprises detecting the shadow under the sweep hand indicator by at least one of the two detectors.

2. A method as defined in claim 1, wherein said step of illuminating, comprises the step of illuminating the background surface and the sweep hand indicator from a non-orthogonal angle with respect to the background surface and the sweep hand indicator.

3. A method as defined in claim 1, wherein said step of detecting illumination levels comprises detecting illumination levels at two separated areas in the background surface from a non-orthogonal angle with respect to the background surface and the sweep hand indicator.

4. A method as defined in claim 1, further comprising the step of:

providing the detectors in series connection with each other and with a detector output node located between the two detectors;

wherein said step of detecting illumination comprises generating an electrical signal with each detector dependent upon the illumination level in said two separated areas on the background surface, combining the signals generated by said detectors at said detector output node, and comparing the combined signal to a predetermined threshold.

5. A method as defined in claim 1, wherein said step of illuminating comprises the steps of energizing a light emitting diode to emit light and directing light emitted by said light emitting diode onto said two separated areas on the background surface.

6. A method as defined in claim 1, wherein said step of illuminating comprises the steps of energizing an infrared-light emitting diode to emit infrared radiation and directing said infrared radiation onto said two separated areas on the background surface.

7. A method of sensing motion of a sweep hand indicator of a meter which moves adjacent a background surface, the method comprising the steps of:

illuminating the background surface and the sweep hand indicator by an illumination source defining an illumination field having an axis, the axis of illumination field being positioned at a non-orthogonal angle with respect to the background surface;

detecting illumination on the background surface by two photo diodes, each defining a field of view having an axis, the axis of field of view of the two photo diodes being positioned substantially in parallel with each other to detect illumination in two separated background surface areas illuminated by the illumination source;

forming a shadow under the sweep hand indicator upon the sweep hand indicator moving across at least one of said fields of view and upon illumination by the illumination source; and

detecting at least the shadow under the sweep hand indicator by at least one of the two detectors.

8. A method of claim 7, wherein said illumination source comprises an LED.

9. A method as defined in claim 7, further comprising the step of:

providing the diodes in series connection with each other and with a diode output node located between the two diodes;

wherein said step of detecting illumination comprises generating an electrical signal with each diode dependent upon the illumination level in said two separated areas on the background surface, combining the signals generated by said diodes at said diode output node, and comparing the combined signal to a predetermined threshold.

10. A meter reading apparatus to be attached to a utility meter, the apparatus comprising:

an infrared emitter;

at least two photo diodes having detection fields being oriented at two separated areas for detecting light in the two separated areas illuminated by the infrared light emitter, wherein the at least two photo diodes are electrically connected in series with each other and with an output node located between the two diodes; and

a comparison circuit having a first comparison input electrically coupled with the output node and a second comparison input electrically coupled with a reference value circuit.

11. Apparatus as defined in claim 10, further comprising:

a housing;

an alignment unit disposed within the housing, for mounting thereon the infrared emitter and the at least two photo diodes; and

means for mounting the housing to the utility meter.

12. Apparatus as defined in claim 11, wherein the utility meter includes an infrared transparent cover and wherein said means for mounting comprises means for securing the housing to the external surface of the utility meter cover.

13. Apparatus as defined in claim 10, wherein the at least two photo diodes are positioned substantially in parallel with each other and the infrared emitter is positioned at an angle with respect to the at least two photo diodes.

14. A system for remotely detecting the consumption of a consumable, the apparatus comprising:

a utility meter having a meter surface and a sweep hand that moves above the meter surface at a rate dependent upon the consumption of a consumable;

an infrared emitter defining an illumination field having an axis oriented at an angle with respect to the meter surface;

two photo diodes, each defining a respective detection field having an axis, the detection fields being oriented at two separated areas within the illumination field on the meter surface for detecting infrared illumination in the two separated, wherein the two photo diodes are electrically connected in series with each other and with an output node located between the two diodes; and

a comparison circuit having a first comparison input electrically coupled with the output node and a second comparison input electrically coupled with a reference value circuit.

15. A system as defined in claim 14, wherein said utility meter has an outer cover which is transparent to infrared illumination, the system further comprising:

a housing mounted to the external surface of the transparent cover;

an alignment unit disposed within the housing, said alignment unit containing said infrared emitter and photo diodes.