Supervised input converter

• US 7,154,425 B2
• Filed: 08/08/2003
• Issued: 12/26/2006
• Est. Priority Date: 08/08/2003
• Status: Expired due to Term

• Current Assignee: Johnson Controls Tyco IP Holdings LLP (Johnson Controls International plc)
• Original Assignee: Sensormatic Electronics Corporation (Johnson Controls International plc)
• Inventors: Venditti, Robert A., Grigorov, Peter, Zaparovanny, Alexey Y.
• Primary Examiner(s): Young, Brian
• Application Number:
  US10/637,388
• Publication Number:
  US 20050030215A1
• Time in Patent Office: 1,236 Days
• Field of Search: 341/144, 341/155, 341/118, 341/119, 341/120, 341/110, 236/47, 236/46.R, 236/51, 165/11, 165/1, 165/12
• US Class Current: 341/155
• CPC Class Codes: G07C 9/00944 Details of construction or manufacture

Abstract

A multiplexer selects an input signal from one of plural sensors. An A/D converter converts the selected input signal to a digital input value. A processor then determines, based on the digital input value, an output resistance to which the resistance of the selected sensor is to be translated. Finally, the processor controls a digital potentiometer corresponding to the selected sensor to the determined output resistance. In one embodiment, a conditioning circuit adjusts the gain of the input signal according to calibration data, effectively performing at least a part of the translation in the analog domain.

Claims

1. A supervisory input converter, comprising:

a processor;

a multiplexer for selecting, under control of the processor, an input signal from one of plural sensors;

a conditioning circuit which adjusts gain of the input signal;

an analog-to-digital converter which converts the selected input signal to a digital input value, the processor then determining, based on the digital input value, an output resistance to which the resistance of the selected sensor is to be translated; and

a digital potentiometer corresponding to the selected sensor, the processor controlling the digital potentiometer to the determined output resistance.

2. The supervisory input converter of claim 1, further comprising:

at least one lamp providing a status indication.

3. The supervisory input converter of claim 1, further comprising:

non-volatile memory which holds calibration data.

4. The supervisory input converter of claim 1, further comprising:

a serial interface.

5. A method for converting supervised input signals, comprising:

selecting from a plurality of supervised inputs, each supervised input having a corresponding input resistance indicative of said supervised input'"'"'s state;

adjusting gain of a signal from the selected supervised input signal, said signal prior to adjustment being indicative of said supervised input'"'"'s resistance;

converting the selected supervised input'"'"'s input resistance to a digital input value; and

controlling a digital potentiometer to a desired output resistance responsive to the digital input value.

6. An apparatus for converting supervised input signals, comprising:

means for selecting from a plurality of supervised inputs, each supervised input having a corresponding input resistance indicative of said supervised input'"'"'s state;

means for converting the selected supervised input'"'"'s input resistance to a digital input value;

means for adjusting gain of a signal from the selected supervised input signal, said signal prior to adjustment being indicative of said supervised input'"'"'s resistance; and

means for controlling a digital potentiometer to a desired output resistance responsive to the digital input value.