Abstract: A colorimetric analyzer includes a reaction chamber configured to receive a sample and at least one reagent. A measurement cell is operably coupled to the reaction chamber. The colorimetric analyzer has an illumination source configured to emit illumination at a first wavelength during a first absorbance measurement and at a second wavelength during a second absorbance measurement. The colorimetric analyzer also includes an illumination detector spaced from the illumination source such that illumination from the illumination source passes through the measurement cell to the illumination detector. A controller is coupled to the illumination source and the illumination detector. The controller is configured to detect an obstruction of light between the illumination source and the illumination detector based on the first and the second absorbance measurements.

Abstract: A colorimetric analyzer includes a reaction chamber configured to receive a sample and at least one reagent. A measurement cell is operably coupled to the reaction chamber. The colorimetric analyzer has an illumination source configured to emit illumination at a first wavelength during a first absorbance measurement and at a second wavelength during a second absorbance measurement. The colorimetric analyzer also includes an illumination detector spaced from the illumination source such that illumination from the illumination source passes through the measurement cell to the illumination detector. A controller is coupled to the illumination source and the illumination detector. The controller is configured to detect an obstruction of light between the illumination source and the illumination detector based on the first and the second absorbance measurements.

Abstract: A method of measuring low conductivity of a liquid sample using a contacting-type conductivity sensor is provided. The method includes applying a first excitation current to a contacting-type conductivity sensor at a first drive frequency. A first voltage response to the first excitation current is determined. A second excitation current is applied to the contacting-type conductivity sensor at a second drive frequency higher than the first drive frequency. A second voltage response to the second excitation current is determined. A conductivity output is provided based, at least in part, on the first and second voltage responses. A system for measuring conductivity of a liquid at or below 100 ?S/cm is also provided.

Abstract: An in situ flue gas analyzer includes a probe extendable into a flue. The probe has a measurement cell providing a signal responsive to a concentration of a gas within the flue. A controller is coupled to the probe and configured to provide an output based on the signal from the measurement cell. A first media access unit is coupled to the controller and is operably coupleable to a first process communication link. The first media access unit is configured to communicate in accordance with an all-digital process communication protocol. A second media access unit is coupled to the controller and is operably coupleable to a second process communication link. The second media access unit is configured to communicate in accordance with a second process communication protocol that is different than the all-digital process communication protocol. The first and second media access units are enabled simultaneously.

Abstract: A method of measuring impedance of a pH electrode is provided. A test current is applied to the pH electrode for a time duration that is less than 50 percent of a time constant that is associated with electrical characteristics of the pH electrode. A voltage response of the pH electrode is measured when the test current is applied to the pH electrode. An impedance of the pH electrode is calculated as a function of the voltage response.

Abstract: A process analytic sensor is provided. The process analytic sensor includes a process analytic sensing element that is coupleable to a process. The process analytic sensing element has an electrical characteristic that varies with an analytical aspect of the process. A microcontroller is disposed within the process analytic sensor and is coupled to the process analytic sensing element to sense the electrical characteristic and provide an analytical signal based on the sensed characteristic. The microcontroller is operable on as little as 0.5 milliamps and includes electrically erasable programmable read only memory (EEPROM) that can be written while the microcontroller operates on as little as 0.5 milliamps.

Abstract: An improved contacting-type conductivity measurement system and method are provided. A first conductivity measurement is obtained by driving a contacting-type conductivity sensor with an excitation voltage at a first frequency, a second conductivity is obtained by driving the contacting-type conductivity sensor with the excitation voltage at a second frequency. The first and second conductivity measurements are used to provide a more accurate conductivity output.

Abstract: An improved contacting-type conductivity measurement system and method are provided. A first conductivity measurement is obtained by driving a contacting-type conductivity sensor with an excitation voltage at a first frequency, a second conductivity is obtained by driving the contacting-type conductivity sensor with the excitation voltage at a second frequency. The first and second conductivity measurements are used to provide a more accurate conductivity output.

Abstract: A method of measuring impedance of a pH electrode is provided. A test current is applied to the pH electrode for a time duration that is less than 50 percent of a time constant that is associated with electrical characteristics of the pH electrode. A voltage response of the pH electrode is measured when the test current is applied to the pH electrode. An impedance of the pH electrode is calculated as a function of the voltage response.

Abstract: An improved flow-through conductivity sensor is provided. The sensor includes a current return path that has a current return conductor. At least one toroid of the sensor is removed from the flow path and configured to interact with the current return conductor to provide an indication of conductivity. Additional aspects of the invention include disposing a pair of toroids about the current return conductor; disposing a toroid about the current return conductor and configuring the toroid as a transformer.

Abstract: A turbidity sensor includes a sensor body, a primary illuminator, a scattered light detector and a bubble illuminator. The sensor body is disposed to contact a liquid sample. The primary illumination source is disposed to direct illumination into the liquid sample. The scattered illumination detector is disposed proximate a portion of the sensor body that is straight in at least one dimension, and the detector is configured to detect illumination from the primary illumination source that is scattered within the liquid sample. A bubble illuminator is disposed to direct illumination along the at least one dimension. Scattered light that originates from the bubble illuminator is detected by the scattered light detector and provides an indication of bubbles proximate the scattered light detector. Methods of filtering and selectively updating a running average of turbidity readings are also disclosed.

Abstract: A turbidity measurement system with an improved thermal behavior is provided. A turbidity measurement system includes an analyzer and one or more turbidity sensors. Each turbidity sensor includes a source of illumination and a semiconductor-based illumination sensor. The dark current of the semiconductor-based illumination sensor is measured when no illumination is provided by the source. This measured dark current is then used to provide a dark current-compensated turbidity measurement.

Abstract: An improved flow-through conductivity sensor is provided. The sensor includes a current return path that has a current return conductor. At least one toroid of the sensor is removed from the flow path and configured to interact with the current return conductor to provide an indication of conductivity. Additional aspects of the invention include disposing a pair of toroids about the current return conductor; disposing a toroid about the current return conductor and configuring the toroid as a transformer.

Abstract: A pH analyzer is operated to measure conductivity of a solution by applying a substantially DC current having peak values, IREF−PEAK, to a reference electrode of an ion-sensitive sensor having an ion-specific electrode in contact with the solution. The reference electrode is coupled to the ion-specific electrode through the solution. The peak voltage, VION−PEAK, between the ion-specific electrode and the common electrode is measured, and the conductivity of the solution is identified based on C SOL = I REF - PEAK V ION - PEAK .

Abstract: A circuit includes an integrator arranged to integrate input signals over a predetermined sample period based on the cycle period of a power source signal. A delay is coupled to the integrator and is responsive to the end of a sample period to delay start of a successive sample period for a predetermined time delay to cancel low frequency noise induced into the circuit during a prior sample period.

Abstract: A pH analyzer is operated to measure pH of a solution by applying a reference electrode current, IREF, to a reference electrode of a pH sensor and an ion-specific electrode current, IGLASS, to an ion-specific electrode of the pH sensor. The currents to the reference electrode and ion-specific electrode are multiplexed to avoid cross-talk. Multiplexing the currents provides a more accurate measurement of electrode impedance for diagnostic purpose. A current spike is optionally added to the reference electrode current to discharge any charge in the solution due to the reference electrode current.

Abstract: A inductive conductivity sensor for measuring conductivity of a fluid includes a housing supporting a controlled impedance loop and a transducer. The transducer includes a driver for inducing a first current into the fluid adjacent the housing, and for inducing a second current into the controlled impedance loop. The transducer further includes a detector for inductively measuring the first and second currents.

Abstract: A pH analyzer is operated to measure pH of a solution by applying a reference electrode current, IREF to a reference electrode of a pH sensor and an ion-specific electrode current, IGLASS, to an ion-specific electrode of the pH sensor. The currents to the reference electrode and ion-specific electrode are multiplexed to avoid cross-talk. Multiplexing the currents provides a more accurate measurement of electrode impedance for diagnostic purpose. A current spike is optionally added to the reference electrode current to discharge any charge in the solution due to the reference electrode current.