Apparatus for selectively measuring ions in a liquid

Details Apparatus for selectively measuring ions in a liquid Apparatus for selectively measuring ions in a liquid

1984-08-16

1986-05-20

Kaplan, G. L.

Chemistry: electrical and wave energy

Apparatus

Electrolytic

204412, 204416, 357 2313, 357 25, G01N 2730

Patent

active

045899703

ABSTRACT:
The apparatus (14) is constructed and arranged to measure ions in a liquid (30) and comprises a measuring circuit (10) including an ISFET (16), a reference electrode (32), an amplifier (22) and a protection system (12)/guard circuit (40) connected to the measuring circuit (10). The protection system 12/guard circuit 40 comprises at least one electrode (46 or 47) connected via a low-impedance contact (or ring 62/46 or ring electrode 42) to the liquid (30) and coupled to the ISFET (16) by a protective element (64; 65, 66; or 68 and/or 50; 51, 52; 54; 56; or 58) having a low-impedance for high voltages and a high resistance to low voltages.
In one preferred embodiment, the ISFET (16) is provided on a chip (90) and has an electrode (46/62) in as closely spaced relationship as possible to the gate region (34) of the ISFET (16).

REFERENCES:
patent: 4020830 (1977-05-01), Johnson et al.
patent: 4086642 (1978-04-01), Yoshida et al.
patent: 4397714 (1983-08-01), Janata et al.
patent: 4411741 (1983-10-01), Janata
patent: 4514646 (1985-04-01), Ando et al.
Rosemary Smith et al., Sensors and Actuators, 5, pp. 127-136, (1984).
Thesis of Rosemary Smith entitled: "Ion-Sensitive Field Effect Transistors with Polysilicon Gates", Department of Engineering, The University of Utah, Jun. 1982.

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