Fisher Scientific Company

Allied Corporation

John T Schneider

Dennis A Gibboney

Frank R Frola

Dominick Frollini, Jr

Jerry C Premus

A microprocessor-controlled pH and ion concentration meter is disclosed with improved testing procedures. The meter can be tested for excessive internal bias current by measuring the potential (V1) when the meter is connected to a circuit a known voltage (E1) of low impedance and the potential (V2) when the meter is connected to a circuit of the same voltage source (E1) but of known high impedance and having the meter compare (V2-V1) to a preset limit value. The meter can be tested for low internal impedance by further measuring the potential (V4) when the meter is connected to a circuit of a second external voltage (E2) and the known high impedance (R1). The meter then calculates:

Measurement of pH and specific ion concentration

A microprocessor-controlled pH and ion concentration meter is disclosed with improved calibration and testing procedures. For calibration (standardization), the meter stores number pairs (pX.sub.a, E.sub.a), (pX.sup.b, E.sub.b) where the pX values may be pH values (e.g., 4.00 and 7.00) and the E values are expressed in mV/deg K. When multiple standard values are stored, remeasuring one (e.g., replacing E.sub.a1 by E.sub.a2) can be used to update the others (e.g., E.sub.b1 to E.sub.b2) without remeasurement by applying the formula:

Apparatus for controlling the speed of a motor which includes a switch connected in series with the motor for controllably conducting an A.C. signal to the motor and means for controlling the switch which includes first means for generating a series of pulses at a frequency which may be varied according to an input signal, second means for generating a pulse once per cycle at a zero crossing of the A.C. signal, third means for generating a pulse at said A.C. signal zero crossing if a pulse was produced by the first generating means during the A.C. cycle immediately preceding said zero crossing, and fourth means responsive to the output of the third generating means for generating a pulse which is supplied to and renders conductive said switch for one complete A.C. cycle.

Variable motor speed control

An improved method of potentiometrically titrating a sample to an unknown endpoint or endpoints is disclosed. The method includes delivering a titrant to the sample until an endpoint or endpoints are reached, while continuously monitoring the volume of the titrant delivered to the sample and continuously monitoring the potential of the sample during titration. The improvement in the method is accurately determining the endpoint or endpoints by establishing a substantially constant rate of change in sample potential during titration proximate to the endpoint or endpoints and maintaining the established rate of change in sample potential by adjusting the rate of delivery of the titrant.

Growing community of inventors

Apollo, PA, United States of America

John T Schneider