Biosensor electrode excitation circuit
First Claim
1. A circuit for applying a potential to a biosensing electrode, said electrode, when properly inserted in a connector, contacted by a pair of spaced-apart contacts, the combination comprising:
- operational amplifier means having a pair of inputs and an output, one input connected to an excitation potential;
switch means coupled between said operational amplifier means and a first of said contacts, said switch means exhibiting an internal impedance;
feedback circuit means connected between a second of said contacts and a second input to said operational amplifier means, to feed back the potential at said second contact to said second input, whereby the output of said operational amplifier means is maintained at a level which compensates for a potential drop across said switch means and applies to said first contact a potential bearing a predetermined relationship to said excitation potential.
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Abstract
A circuit is described for applying a potential to an electrode of a biosensing test cell, which electrode, when properly inserted in a female connector, is contacted by a pair spaced apart contacts. The circuit includes a source of excitation potential and an operational amplifier having one input connected to the source of excitation potential. A switching circuit is coupled between the operational amplifier and a first one of the spaced apart contacts, with the switch means exhibiting an impedance. A feedback circuit is connected between the second of the spaced-apart contacts and another input to the operational amplifier, to feed back a potential appearing at the second contact. The feedback is for the purpose of maintaining the output of the operational amplifier at a level which compensates for impedance losses in the swtiching circuit. The feedback circuit enables the output of the operational amplifier to be varied so that the potential applied to the electrode is equal to the source of excitation potential. A further circuit is connected to the feedback circuit for sensing when an open or high impedance state exists between the spaced-apart contacts.
317 Citations
6 Claims
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1. A circuit for applying a potential to a biosensing electrode, said electrode, when properly inserted in a connector, contacted by a pair of spaced-apart contacts, the combination comprising:
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operational amplifier means having a pair of inputs and an output, one input connected to an excitation potential; switch means coupled between said operational amplifier means and a first of said contacts, said switch means exhibiting an internal impedance; feedback circuit means connected between a second of said contacts and a second input to said operational amplifier means, to feed back the potential at said second contact to said second input, whereby the output of said operational amplifier means is maintained at a level which compensates for a potential drop across said switch means and applies to said first contact a potential bearing a predetermined relationship to said excitation potential.
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2. The circuit of claim I where a high impedance between said spaced-apart contacts causes an alteration in feedback potential on said feedback circuit means, the combination further comprising:
signal means connected to said feedback circuit means for signalling the presence of said altered feedback potential, to indicate a malfunction with respect to said circuit. - View Dependent Claims (3, 4, 5, 6)
Specification