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: A method of operating a process a combustion analyzer having a measurement cell is provided. The method includes exposing the measurement cell to exhaust of a combustion process where fuel and oxygen are combined in a burner to produce a flame. The measurement cell is heated to a temperature above a flashpoint of the fuel. When a condition is detected, such as a fault or abnormal situation, gas is directed to the measurement cell to form a gaseous barrier between the measurement cell and unburned fuel while the detected condition exists.

Abstract: A process analytic instrument includes an analytical module configured to analyze a process fluid and a removable tube carrier coupled to the analytical module. The analytical module has a plurality of inlet ports in a sealing surface. The removable tube carrier has an end with a plurality of apertures aligned with the plurality of inlet ports of sealing surface of the analytical module. The removable tube carrier fluidically couples a plurality of tubes to the analytical module when the end of the removable tube carrier is biased into the sealing surface of the analytical module.

Abstract: A process analytic device includes a metallic enclosure having electronics disposed therein. The enclosure has an enclosure wall with a reference surface. A plurality of operating rods is provided. Each operating rod is configured to pass through an aperture in the enclosure wall and to cooperate with the enclosure wall to provide a flame quenching pathway. A plurality of electrical switches is provided where each electrical switch is aligned with a respective operating rod, and is mounted a controlled distance from the reference surface. Each operating rod transfers movement to a respective electrical switch through the flame quenching pathway.

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: A free chlorine measurement system and sensor are provided. In accordance with one aspect of the invention, the sensor has a porous working electrode disposed in an electrolyte proximate a porous membrane. The membrane allows free chlorine therethrough where it is reduced and generates a current. The current is related to the free chlorine concentration. The internal electrolyte solution is pH stabilized with a long-term pH stabilizer that has a solubility in water at room temperature between about 1.2 moles/liter and about 0.001 moles/liter. The stabilizer can be an acid or a base depending on whether the pH is to be stabilized at a relatively low value or a relatively high value respectively.

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 dissolved oxygen measurement system, and a method for calibrating a dissolved oxygen analyzer are provided. The method includes directing a pressurized cleaning fluid, having a known oxygen content, upon a sensing surface of a dissolved oxygen sensor disposed in a fluid. Then, the analyzer waits until the dissolved oxygen sensor response to the pressurized cleaning fluid is relatively stable, and stores a calibration value relative to the dissolved oxygen sensor response to the pressurized cleaning fluid. A dissolved oxygen measurement system is also provided. The system includes a dissolved oxygen sensor disposed in a fluid and a first source of a first compressed cleaning fluid that has a first dissolved oxygen content. A dissolved oxygen analyzer is coupled to the dissolved oxygen sensor and to the first valve and is configured to obtain a first calibration value related to the first dissolved oxygen content.

Abstract: Sulfur resistant sensors and a process analytic system employing such sensors are provided. The sensors generally include a treatment or material that is adapted to increase the resistance of certain portions of the sensors to exposure to sulfur. In one aspect, an improved sulfur-resistant process analytic system includes a probe with one or more sulfur-resistant sensors therein coupled to a controller, a thermal control module, and a source of blowback gas.

Abstract: A sensor for analyzing a liquid sample is provided. The sensor includes a sensor body defining a chamber therein. A sensing cell is disposed within the chamber and is adapted to contact the sample solution. The sensing cell has a sensing cell fill solution therein, and a sensing electrode disposed within the sensing cell fill solution. A reference fill solution is disposed within the sensor body. A reference junction is arranged to contact the reference fill solution and the sample solution. A temperature sensitive device is disposed within the body and is configured to provide a temperature sensitive device output. A reference electrode is disposed within the sensor body in contact with the reference fill solution. A solution ground electrode is disposed within the sensor body and spaced from the reference electrode.

Abstract: A dissolved oxygen measurement system, and a method for calibrating a dissolved oxygen analyzer are provided. The method includes directing a pressurized cleaning fluid, having a known oxygen content, upon a sensing surface of a dissolved oxygen sensor disposed in a fluid. Then, the analyzer waits until the dissolved oxygen sensor response to the pressurized cleaning fluid is relatively stable, and stores a calibration value relative to the dissolved oxygen sensor response to the pressurized cleaning fluid. A dissolved oxygen measurement system is also provided. The system includes a dissolved oxygen sensor disposed in a fluid and a first source of a first compressed cleaning fluid that has a first dissolved oxygen content. A first valve is operably coupled to the first source and configured to selectively direct the first compressed cleaning fluid against a sensing surface of the dissolved oxygen sensor.

Abstract: A contacting-type conductivity sensor includes a plurality of electrodes disposed on a distal surface of a substrate. The substrate includes a plurality of vias through which electrical interconnection to the electrodes is accomplished. The conductivity sensor can employ two or four electrodes and may have a temperature sensitive element disposed on the distal surface. The electrodes may be patterned or otherwise deposited using semiconductor processing techniques.

Abstract: Measurement of arsenic in an aqueous solution is provided. The pH of the aqueous solution is adjusted to a pH of about 7.0 or higher. The pH adjusted aqueous solution is then analyzed using anodic stripping voltammetry to obtain an indication of a quantity of arsenic in the solution. In one aspect, the pH is adjusted using a phosphate buffer.

Abstract: A dissolved oxygen sensor having a cathode and anode immersed in an electrolyte is designed to provide a low background current in the sensor when a potential is applied to the cathode. The background current is maintained at a desired level by selecting the area and length of a channel or path of diffusion of residual oxygen in the electrolyte to the cathode. The area (A) of the diffusion channel in relation to its length (L) is selected to be at or below a selected ratio, A/L.

Abstract: An electrochemical cell includes a measuring electrode and a reference electrode. The reference electrode includes a flowing liquid junction between a reference fill fluid and a sample. The flowing liquid junction is configured to inhibit particles from blocking or obstructing it. In one aspect a particle filter is provided before the flowing liquid junction to prevent particles from the fill fluid from entering the flowing liquid junction. In another aspect a particle filter is provided after the flowing liquid junction to prevent particles in the sample from entering the flowing liquid junction. In another aspect the flowing liquid junction has a diameter that generally increases from an aperture proximate the fill fluid to an aperture proximate the sample. On example of such a configuration is a tapered flowing liquid junction.

Abstract: An integrated luminescence sensor includes a light pipe in optical communication with a luminescence sensing layer. A source of excitation illumination is coupled to the light pipe and disposed to direct excitation illumination toward the sensing layer. A luminescent light detector is also coupled to the light pipe and is disposed to detect luminescent illumination luminescing from the sensing layer, which luminescence is related to interaction between the sensing layer and a substance of interest.

Abstract: Modification of ruthenium complex luminescence dye for oxygen sensing is provided. Generally, modification includes bonding long chain hydrophobic organic groups to the ligands of the ruthenium complex in order to increase solubility of the ruthenium complex in non-polar organic solvents. A sensor manufacture using the modified ruthenium complex luminescence dye is also provided.

Abstract: A control system includes a measurement device capable of gathering high frequency process parameter data, a modeling routine which uses the high frequency parameter data to develop a model of the high frequency noise and a compensation routine that employs the developed model to adjust a control signal to thereby compensate for the high frequency noise present within the process parameter. The measurement device may measure a process variable at a relatively high frequency and send a subset of the measured data (e.g., the low frequency data) to a standard controller that generates a control signal to control the measured process parameter in any known manner. The modeling routine analyzes the high frequency data and develops a mathematical model of the high frequency noise within the process variable.

Abstract: A chloramine amperometric sensor includes a sensor body with an electrolyte disposed inside the sensor body. A membrane is coupled to the sensor body and adapted to pass chloramine therethrough. A reference electrode is disposed in the electrolyte and coupled to a first conductor. A second conductor is coupled to a working electrode that is disposed proximate the membrane. The working electrode is constructed from a noble metal in non-compact form. The non-compact form can be a Gas Diffusion Electrode, which can include metal mesh, carbon paper, carbon cloth, metal/carbon powder loaded on a porous membrane or any combination thereof.