Abstract: An ozone concentration sensor for use with an ozone generator. The ozone free feed gas to the ozone generator is briefly fed to the sensor which measures both the temperature of the feed gas and the time it takes a high frequency sound pulse to travel a predetermined distance in the feed gas for reference date. A portion of the output gas from the ozone generator is then fed to the sensor and the same measurements are made for the output gas. A programmed microcomputer determines the ozone concentration in the output gas from the measurements. In one embodiment, the sensor constantly receives output gas from the ozone generator. The reference measurements are made while operation of the ozone generator is briefly interrupted and feed gas passes through the ozone generator unchanged. Reference measurements may be stored and used for repeated ozone concentration calculations, so long as there is no significant change in the feed gas.

Abstract: A gas concentration and/or bulk flow rate sensor suitable for measuring the oxygen concentration and the bulk flow rate of gas delivered to a patient for medical purposes. Two piezoelectric transducers mounted on a printed circuit board are interconnected by an elongated coiled tube. The gas is flowed around one of the transducers, through the tube and around the other transducer. Periodically, one of the transducers is energized with a single short duration pulse to transmit a sonic wave through the gas to the other transducer. The travel time for the sonic wave is measured. The two transducers are alternately used as transmitters and receivers so that the wave travel time is measured both with and against the gas flow direction. A thermistor is located in the center of the coiled tube for measuring the temperature of the gas. From the measured times, the measured temperature and stored formulas, a microprocessor calculates the oxygen concentration and/or the bulk flow rate for the gas.

Abstract: 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:E.sub.b2 =E.sub.b1 +(E.sub.a2 -E.sub.a1).Additionally, the meter can be tested for excessive internal bias current by measuring the potential (V1) when the meter is connected to a circuit of low impedance and the potential (V2) when the meter is connected to a circuit of the same voltage source but of known high impedance and having the meter compare (V2-V1) to a preset limit value.

Abstract: 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.

Abstract: Our system for determining the sulfur content of a sample includes combusting the sample to form a gas in which the sulfur is converted primarily to sulfur dioxide in known ratio with the sulfur trioxide. The gas sample is passed into a reaction vessel containing a substantially pyridine solvent. The sulfur dioxide is scrubbed from the sample (trapping) via a binding action with the pyridine. The bound sulfur dioxide is titrated with elemental iodine in the presence of alcohol and excess water. The trapping and titration sequence can be simultaneous and continuous. A polarized electrode pair is preferably employed as the detection means with the end point determination occurring when the electrodes become current conducting in the presence of excess iodine. The titrant volume is then converted to a sulfur analysis by standard means. The apparatus is disclosed for carrying out the method.