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Abstract

Apparatus and method are provided to ensure accuracy of a measurement signal obtained using a potentiometric sensor placed in a solution. The apparatus includes an interface amplifier that generates a relatively large turn-on bias current whenever the amplifier is initially powered on. To avoid polarization of the potentiometric sensor by the turn-on bias current, a switch device is used to direct the turn-on bias current along a path away from the potentiometric sensor. The switch device is controlled using a timer circuit that causes a change in position of the switch device after a predetermined time delay. During the time delay, the bias current reduces to a normal value and polarization of the potentiometric sensor has been avoided. An accurate measurement of a physical parameter associated with the solution can then be taken without the detrimental effect of the turn-on bias current on the potentiometric sensor. The apparatus has particular utility in obtaining water quality data, such as hydrogen potential, specific ion potential and oxygen reduction potential.

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First Claim