Abstract: A gas sensor which works according to the principle of thermal conductivity is functionally tested. In the method, a calibration cycle is conducted in which a membrane of the gas sensor is immersed in a fluid calibration medium having a known concentration of a target gas. After the calibration cycle, a measurement chamber of the gas sensor is purged with a purging gas. Then, a measuring cycle is conducted, using a thermal conductivity sensor to measure the target gas in the measurement chamber. Using a calibration baseline established from the calibration cycle and a measurement baseline in the measurement cycle, a baseline comparison value is obtained and compared to a predetermined baseline threshold value. An error message, indicating a malfunction in the purging gas supply, is generated when the baseline comparison value exceeds the predetermined baseline threshold value.

Abstract: A gas sensor which works according to the principle of thermal conductivity is functionally tested. In the method, a calibration cycle is conducted in which a membrane of the gas sensor is immersed in a fluid calibration medium having a known concentration of a target gas. After the calibration cycle, a measurement chamber of the gas sensor is purged with a purging gas. Then, a measuring cycle is conducted, using a thermal conductivity sensor to measure the target gas in the measurement chamber. Using a calibration baseline established from the calibration cycle and a measurement baseline in the measurement cycle, a baseline comparison value is obtained and compared to a predetermined baseline threshold value. An error message, indicating a malfunction in the purging gas supply, is generated when the baseline comparison value exceeds the predetermined baseline threshold value.

Abstract: An electrochemical sensor for measuring the oxygen partial pressure in a process fluid, comprises an electrolyte-filled sensor body, which is covered on one side charged with the process fluid by an oxygen-permeable membrane, a cathode on the membrane, an annular guard electrode surrounding the cathode, which in measuring operation lies at the same potential as the cathode, an anode charged by the electrolyte in the sensor body, a reference electrode charged by the electrolyte in the sensor body, wherein between the anode and cathode a voltage can be applied, which is controlled between the cathode (8) and reference electrode at a constant polarization voltage and the measuring sensor current flowing in measuring operation between the cathode and anode is a measure for the oxygen partial pressure in the process fluid, and a test voltage source which can be switched in a testing mode between the cathode and guard electrode for producing test oxygen in the electrolyte and/or in the process fluid between the

Abstract: An electrochemical sensor for measuring the oxygen partial pressure in a process fluid, comprises an electrolyte-filled sensor body, which is covered on one side charged with the process fluid by an oxygen-permeable membrane, a cathode on the membrane, an annular guard electrode surrounding the cathode, which in measuring operation lies at the same potential as the cathode, an anode charged by the electrolyte in the sensor body, a reference electrode charged by the electrolyte in the sensor body, wherein between the anode and cathode a voltage can be applied, which is controlled between the cathode (8) and reference electrode at a constant polarization voltage and the measuring sensor current flowing in measuring operation between the cathode and anode is a measure for the oxygen partial pressure in the process fluid, and a test voltage source which can be switched in a testing mode between the cathode and guard electrode for producing test oxygen in the electrolyte and/or in the process fluid between the

Abstract: The functioning of an amperometric electrochemical sensor having an electrochemical cell is monitored by the electrochemical cell. A perturbation quantity is imposed on the sensor, which is operated with voltage control at a given polarization voltage. The response to the perturbation is measured and a check value is calculated, using the response under the perturbation as an input value. The check value is compared to a system-dependent limit value. If the check value is larger than the system-dependent limit value, the initial polarization voltage is changed by a predefined voltage increment and the process is repeated, until an optimal polarization voltage has been found, i.e., until the calculated check value is smaller than the system-dependent limit value. A measuring system that serves to carry out the method is also described. An automated embodiment utilizes a computer-supported control- and processing-unit with a data memory and a data-evaluating program.

Abstract: An exemplary method is disclosed which serves to determine a condition of at least one measuring probe which is integrated in a process vessel of a process system with one or more system stages and which is cleaned from time to time using, for example, CIP- and SIP processes, without uninstalling the measuring probe for the cleaning. The temperature of the measuring probe or of the medium surrounding the measuring probe can be measured by a measuring sensor arranged inside or outside the measuring probe, and the condition of the measuring probe can be determined based on a record of the temperature (TS/M) measured over the time when the measuring probe is in operation. In some cases, the method can include monitoring correct execution of the CIP- and SIP processes.

Abstract: The functioning of an amperometric electrochemical sensor having an electrochemical cell is monitored by the electrochemical cell. A perturbation quantity is imposed on the sensor, which is operated with voltage control at a given polarization voltage. The response to the perturbation is measured and a check value is calculated, using the response under the perturbation as an input value. The check value is compared to a system-dependent limit value. If the check value is larger than the system-dependent limit value, the initial polarization voltage is changed by a predefined voltage increment and the process is repeated, until an optimal polarization voltage has been found, i.e., until the calculated check value is smaller than the system-dependent limit value. A measuring system that serves to carry out the method is also described. An automated embodiment utilizes a computer-supported control- and processing-unit with a data memory and a data-evaluating program.

Abstract: An exemplary method is disclosed which serves to determine a condition of at least one measuring probe which is integrated in a process vessel of a process system with one or more system stages and which is cleaned from time to time using, for example, CIP- and SIP processes, without uninstalling the measuring probe for the cleaning. The temperature of the measuring probe or of the medium surrounding the measuring probe can be measured by a measuring sensor arranged inside or outside the measuring probe, and the condition of the measuring probe can be determined based on a record of the temperature (TS/M) measured over the time when the measuring probe is in operation. In some cases, the method can include monitoring correct execution of the CIP- and SIP processes.