The present invention appropriately determines a time to replace a responsive glass membrane for measuring a sample containing hydrofluoric acid. A measurement device for measuring a hydrogen ion concentration of a liquid sample containing hydrofluoric acid, the measurement device including a glass electrode that measures a hydrogen ion concentration in the liquid sample, the glass electrode including a responsive glass membrane, a membrane resistance measurement unit that measures a membrane resistance value of the responsive glass membrane, a temperature measurement unit that measures a temperature of an environment in which the responsive glass membrane is disposed, and an output unit that outputs a replacement index for replacing the responsive glass membrane based on the membrane resistance value and the temperature.

An online calibration system for an electrochemical sensor. The calibration system comprises a calibration electrode coupled with a redox species, where the redox species is configured to control a pH of a reference solution local to the calibration electrode, such that when a voltammetric signal is applied to the calibration electrode the output generated from the calibration system is determined by the local environment pH. The output signal from the calibration system is used to calibrate a reference potential generated by a reference system of the electrochemical sensor to correct for drift in the reference potential when the electrochemical sensor is being used. The calibration electrode may be disposed in a reference cell of the electrochemical sensor.

Disclosed herein are devices and methods for determining the pH of fluid. Example devices include a device comprising a surface configured to contact the fluid and a pH indicator covalently bound thereto, wherein the pH indicator has a first color prior to contact with the fluid and changes color as a function of the pH of the fluid.

A self-vibrating pH probe comprise a housing containing an electronic assembly to which is coupled a vibration source element so that at least a portion of vibrations caused by the vibration source element propagate to the electronic assembly, the vibration source element being controllable for at least on/off operation. The self-vibrating pH probe further comprising a pH probe member having a probe tip at a first end, the probe member extending from the housing and mechanically and electrically coupled by a second end to the electronic assembly so that at least a portion of vibrations propagating to the electronic assembly further propagate to the probe tip; and further including a processor coupled to the electronic assembly for coordinating operation of the vibration source element and operation of the pH probe member.

A simplified, rigorous and accurate method of measuring pH of an analyte solution with extreme precision, which does not cause errors against actual pH through compensating a pH variation by a liquid temperature or a concentration of potassium chloride of an internal liquid in a glass electrode or a reference electrode when pH is measured with respect to various analyte solutions such as a sample solution having a high concentration of salts, a sample solution contaminated with salts and a sample solution having a low concentration of salts.

An ion sensor apparatus comprises at least one ion sensitive field effect transistor (ISFET) device configured to be exposed to a liquid, a reference electrode configured to contact the liquid to which the ISFET device is exposed, and at least one magnet configured to intermittently expose the ISFET device to a magnetic field. A processor is operatively connected to the ISFET device and the reference electrode. The processor modulates the magnetic field to produce a corresponding modulated output in resistance of the ISFET device, and modulation of a reported output value of the ion sensor apparatus.

A method for determining a state of a measuring transducer integrated in a process container, wherein in the process container one or more processes are being performed, and the measuring transducer registers at least one physical or chemical process parameter within the process container, includes steps as follows: identifying a process currently being performed in the process container; and ascertaining a deviation value as measure of a deviation of a measured value progression registered by the measuring transducer during the process currently being performed in the process container from a measured value progression expected for the identified process, wherein the state of the measuring transducer and/or of the process is determined utilizing the ascertained deviation value.

ISFET measuring probe with a housing in which an ISFET and a reference electrode are arranged in such a way that the gate electrode of the ISFET, which is coated with an ion-sensitive layer, and the reference electrode reach into a measurement space into which a measurement medium can be introduced, with the distinguishing feature that an auxiliary electrode is arranged additionally inside the housing and is held inside the measurement space.

An electrode cleaning and calibration system generally comprises a sensor holder assembly machined from a block of solid acrylic or similar plastic material, which can accommodate a variety of types and sizes of sensors for use in monitoring and measurement of water processing and treatment processes. Examples of sensors suitable for use in the system include pH sensors, dissolved oxygen sensors, chlorine sensors, ozone sensors, total suspended solid sensors, mixed liquor suspended solid sensors, ammonia sensors, monochloramine sensors, and ultraviolent transmittance sensors.

A device (1) for determining a measured variable, that allows an as simple as possible adaptation to the measurement conditions, is achieved in that the device (1) has a sensor unit (2) and a transmitter (3). The sensor unit (2) generates an electric primary signal in dependence on the measured variable, and communicates the primary signal via an analog output interface (4) to the transmitter (3) which processes the primary signal. Furthermore, the sensor unit (2) and transmitter (3) are advantageous by themselves, and the sensor unit (2) preferably allows for offline calibration under constant surrounding conditions.