Drift calibration method and device for the potentiometric sensor
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.
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 SnO 2 pH sensor.
3. The apparatus in claim 1 , wherein said second sensing element comprises a potentiometric sensor including a potentiometric SnO 2 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.