Increasing resolution of resistance measurements

Patent metadata

Field	Value
Publication number	US-9429606-B2
Application number	US-201314041149-A
Country	US
Kind code	B2
Filing date	Sep 30, 2013
Priority date	Sep 30, 2013
Publication date	Aug 30, 2016
Grant date	Aug 30, 2016

Abstract

Increasing the resolution of a resistance sensor by adjusting a current source.

First claim

What is claimed is:

1. A method of increasing resolution of resistance sensing, includes the steps of:
determining a maximum resistance position of a resistive device;
sensing a voltage that is generated by passing a current through the resistive device when the resistive device is at the maximum resistance position;
increasing the current generated by a variable current source by increasing the current value, until the voltage that is sensed is near a maximum voltage;
storing the current value used by the variable current source associated with the maximum voltage as a first current value;
determining a minimum resistance position of the resistive device;
sensing the voltage that is generated by passing the current through the resistive device when the resistive device is at the minimum resistance position;
decreasing the current generated by the variable current source by decreasing the current value, until the voltage that is sensed is near a minimum voltage when the device the resistance position;
storing the current value used by the variable current source associated with minimum voltage as a second current value;
determining a maximum resolution step value derived from the minimum resistance position and maximum resistance position; and
changing the current value used by the variable current as the resistance value changes by the maximum resolution step value.

2. The method of claim 1 , where the resistive device is a resistive strip.

3. The method of claim 2 , where setting the maximum resistance position includes opening a sash fully on a fume hood, where the sash is coupled to a traveler on the resistive strip.

4. The method of claim 1 , where setting the minimum resistance position includes closing a sash fully on a fume hood, where the sash is coupled to a traveler on the resistive strip.

5. The method of claim 1 , where the resistive device is a thermistor.

6. The method of claim 1 , further includes:
converting the voltage into a voltage value with an analog-to-digital converter; and
generating the current value with a controller in response to receipt of the voltage value at the controller.

Assignees

• Charles Donald E
• Siemens Industry Inc

Inventors

• Charles Donald E

Classifications

• G01K7/22

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

• G01K7/24 Primary

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

• G01R27/08

  Measuring resistance by measuring both voltage and current · CPC title

• G01R15/09

  Autoranging circuits · CPC title