Drift calibration method and device for the potentiometric sensor

• US 7,981,264 B2
• Filed: 02/09/2006
• Issued: 07/19/2011
• Est. Priority Date: 10/18/2005
• Status: Expired due to Fees

• Current Assignee: Chung-Yuan Christian University
• Original Assignee: Chung-Yuan Christian University
• Inventors: Sun, Tai-Ping, Chou, Jung-Chuan, Pan, Chung-We, Tsai, Chu-Neng, Hsung, Shen-Kan
• Primary Examiner(s): Ruddock; Ula C
• Assistant Examiner(s): Kaur; Gurpreet
• Application Number:
  US11/349,947
• Publication Number:
  US 20070084721A1
• Time in Patent Office: 1,986 Days
• Field of Search: 204/401, 204/406, 204/435, 257/262, 438/199, 438/49, 438/48, 438/104, 438/197, 298/75, 205/777, 436/106, 436/96
• US Class Current: 204/406
• CPC Class Codes: G01N 27/4165 for pH meters

Abstract

The present invention discloses a method and an apparatus of the drift calibration of sensors. The method includes shifting the sensing signal and differential technology to remove the drift signal by time during a long measuring. The apparatus includes two voltage sensors and readout circuits, a signal-shifting circuit and a differential circuit, and the apparatus is used for outputting the response signal without time drifting.

Claims

1. An apparatus for sensor calibration, comprising:

a first sensing element located in a monitoring solution for outputting a first sensing signal;

a second sensing element located in said monitoring solution for outputting a second sensor signal;

a first instrumental differential amplifier for outputting said first sensing signal, wherein a first input end of said first instrumental differential amplifier connects to said first sensing element, and a second input end connects to ground;

a second instrumental differential amplifier for outputting said second sensing signal, wherein a third input end of said second instrumental differential amplifier connects to said second sensing element, and a fourth input end connects to said ground;

a voltage shifting circuit coupled to the output end of said second instrumental differential amplifier for shifting said second operation sensing signal and outputting a third signal proportional to a sensor drift;

a third instrumental differential amplifier, wherein a fifth input end of said third instrumental differential amplifier connects to the output end of said first sensing element, and a sixth input end connects to said voltage shifting circuit for obtaining the potential difference between said first sensing signal and said third signal; and

a reference element located in said monitoring solution, wherein one end of said reference element connects to said ground for providing a constant reference voltage.

2. The apparatus in claim 1, wherein said first sensing element comprises a potentiometric sensor including a potentiometric SnO₂ pH sensor.

3. The apparatus in claim 1, wherein said second sensing element comprises a potentiometric sensor including a potentiometric SnO₂ pH sensor.

4. The apparatus in claim 1, wherein said first instrumental differential amplifier includes the instrumentation amplifier or the differential amplifier.

5. The apparatus in claim 1, wherein said second instrumental differential amplifier includes the instrumentation amplifier or the differential amplifier.

6. The apparatus in claim 1, wherein said voltage shifting circuit comprises a feedback circuit.

7. The apparatus in claim 1, wherein said third instrumental differential amplifier includes the instrumentation amplifier and the differential amplifier.

8. The apparatus in claim 1, wherein said reference element includes a Ag/AgCl reference electrode.

9. The apparatus in claim 1, wherein said first input end is a positive input end.

10. The apparatus in claim 1, wherein said second input end is a negative input end.

11. The apparatus in claim 1, wherein said third input end is a positive input end.

12. The apparatus in claim 1, wherein said fourth input end is a negative input end.

13. The apparatus in claim 1, wherein said fifth input end is a positive input end.

14. The apparatus in claim 1, wherein said sixth input end is a negative input end.

15. The apparatus in claim 1, further comprising a differential circuit wherein a fourth sensing signal is obtained from the difference between the first sensing signal and the third sensing signal and the fourth sensing signal is a response signal in which a drift effect is removed.