Apparatus for increasing resolution of resistance sensing

Patent metadata

Field	Value
Publication number	US-9791486-B2
Application number	US-201615224138-A
Country	US
Kind code	B2
Filing date	Jul 29, 2016
Priority date	Sep 30, 2013
Publication date	Oct 17, 2017
Grant date	Oct 17, 2017

Abstract

An apparatus is provided that increases resolution of a resistance sensor. The apparatus may include a variable current source that produces a variable current in response to a current value. The apparatus may also include a variable resistance device that generates a variable voltage associated with the variable current. The variable resistance may have a low resistance value and a high resistance value. In addition, the apparatus may include a controller that receives a voltage value associated with the variable voltage and controls the current value in order to result in an increase in resolution of a range between the low resistance value and a high resistance value.

First claim

What is claimed is:

1. An apparatus that increases resolution of resistance sensing, comprising:
a controller;
a variable current source that produces a variable current in response to a current value set by the controller;
a variable resistance device that produces a variable resistance and that generates a variable voltage based on both the variable current and on the variable resistance; and
an analog to digital (A/D) converter that produces a voltage value based on the variable voltage,
wherein the controller is configured to:
receive the voltage value;
control the current value via a digital to analog (D/A) converter based on the received voltage value such that the controller causes the current value to be increased and/or decreased to cause the variable voltage to be in a voltage range as the variable resistance changes that is less than a maximum range of voltages capable of being converted by the A/D converter to the voltage value; and
determine the variable resistance based on the received voltage value and the controlled current value.

2. The apparatus of claim 1 , where the variable resistance device includes a resistive strip.

3. The apparatus of claim 2 , where the resistive strip further includes a traveler coupled to a sash of a fume hood, wherein movement of the sash causes the traveler to move across the resistive strip and change the variable resistance.

4. The apparatus of claim 1 , where the variable resistance device is a potentiometer.

5. The apparatus of claim 1 , where the variable resistance device is a thermistor.

6. The apparatus of claim 5 , where the thermistor is associated with a thermostat.

7. The apparatus of claim 1 , wherein the controller is configured to determine a maximum resistance of the variable resistance device and further control the current value based on the determined maximum resistance.

8. The apparatus of claim 7 , wherein the controller is configured to determine the maximum resistance via monitoring the determined variable resistance over time.

9. The apparatus of claim 1 , where the controller is a microcontroller.

Assignees

• Siemens Industry Inc

Inventors

• Charles Donald E

Classifications

• G01R15/09

  Autoranging circuits · CPC title

• G01R27/14

  Measuring resistance by measuring current or voltage obtained from a reference source (G01R27/16, G01R27/20, G01R27/22 take precedence) · CPC title

• G01K7/22

  the element being a non-linear resistance, e.g. thermistor (G01K7/26 takes precedence) · CPC title

• G01K7/24 Primary

  in a specially-adapted circuit, e.g. bridge circuit · CPC title

• G01R27/02 Primary

  Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant (by measuring phase angle only G01R25/00) · CPC title