A sensor element drive circuit is a circuit including a plurality of semiconductor elements formed on a semiconductor substrate for realizing a current control function and a switching function. The current control function is a function of controlling the current flowing between electrodes such that the potential difference between electrodes becomes constant. The switching function is a function for switching between a connected state in which the electrodes are electrically connected to a sensor control apparatus and a cut-off state in which electrical continuity therebetween is broken. When one of an Ip+ terminal, a COM terminal, and a Vs+ terminal is determined to have an anomalous potential, the sensor control apparatus causes the sensor element drive circuit to perform switching from the connected state to the cut-off state, and connects the semiconductor substrate to a negative voltage lower than a ground potential applied to the sensor element drive circuit.

Compensator circuitry is provided for an oxygen sensor which includes a pump cell and a reference cell. The compensator circuitry includes a feedback control loop which maintains the reference cell at a reference voltage. The feedback control loop includes a digital compensator which determines and outputs a compensation current to the pump cell dependent on a reference voltage measured from the reference cell. The digital compensator also suspends the determination and output of the compensation current for a set time which is dependent on detection of edges in an oxygen sensor heater Pulse Width Modulation signal.

A gas sensor includes a sensor element body having a porous layer provided on an outer surface, and a power supply device which supplies power to a heater element that is in the sensor element body. The amount of power being applied to the heater element by the power supply device when gas detection is being performed by the gas sensor in a steady state is designated as P [W], the volume of the length range of a heating region of the heater element provided in the sensor element body as V [mm.sup.3], and the applied power density as X [W/mm.sup.3], where X is a value expressed by P/V. In that case, the following relationship is satisfied between the applied power density X and the average thickness Y [m] of the porous layer:

Y509.322884.89X+5014.12X.sup.2

A control device performs deterioration diagnosis of a gas sensor including a pump cell and a sensor cell. The control device includes a control unit, a determination value acquisition unit, a diagnosis unit, and a correction unit. The control unit temporarily reduces the oxygen removal capability of the pump cell. The determination value acquisition unit acquires an output ratio of the sensor cell based on an output value of the sensor cell in a state where the oxygen removal capability of the pump cell is temporarily reduced. The diagnosis unit performs deterioration diagnosis of the gas sensor by comparing the output ratio with a determination threshold. The correction unit sets a correction coefficient based on an atmospheric pressure and an oxygen concentration, and also corrects the output ratio using the correction coefficient.

An electrochemical cell for sensing gas has added mechanical support for the working electrode to prevent flexure of the working electrode due to pressure differentials. The added mechanical support includes: 1) affixing a larger area of the working electrode to the body of the cell; 2) a gas vent to a cavity of the body to equalize pressures; 3) a rigid electrolyte layer abutting a back surface of the working electrode; 4) infusing an adhesive deep into sides of the porous working electrode to enhance rigidity; 5) supporting opposing surfaces of the working electrode with the rigid package body; and 6) other techniques to make the working electrode more rigid. A bias circuit is also described that uses a controllable current source, an integrator of the varying current, and a feedback circuit for supplying a voltage to the counter electrode and a bias voltage to the reference electrode.

Continuous monitoring of acetone is a challenge using related art sensing methods. Though real-time detection of acetone from different biofluids is promising, signal interference from other biomarkers remains an issue. A minor fluctuation of the signals in the micro-ampere range can cause substantial overlapping in linear/polynomial calibration fittings. To address the above in non-invasive detection, principal component analysis (PCA) can be used to generate specific patterns for different concentration points of acetone in the subspace. This results in improvement of the problem of overlapping of the signals between two different concentration points of the data sets while eliminating dimensionality and redundancy of data variables. An algorithm following PCA can be incorporated in a microcontroller of a sensor, resulting in a functional wearable acetone sensor. Acetone in the physiological range (0.5 ppm to 4 ppm) can be detected with such a sensor.

A biosensor for measuring an electrical response from a biological sample. The biosensor includes a substrate, a passivation layer grown on a surface of the substrate, a patterned catalyst layer deposited on the passivation layer, and three electrodes grown on the patterned catalyst layer. The three electrodes include a working electrode, a counter electrode, and a reference electrode. The working electrode includes a first array of electrically conductive biocompatible nanostructures that is configured to be an attachment site for the biological sample. The counter electrode includes a second array of electrically conductive biocompatible nanostructures that is configured to acquire the electrical response from the working electrode. The reference electrode includes a third array of electrically conductive biocompatible nanostructures that is configured to adjust a specific voltage around the working and the counter electrodes.

A control device of a nitrogen oxide sensor comprises a voltage control part configured to control voltage applied to the pump cell, and a temperature estimation part configured to estimate a temperature of the pump cell. The voltage control part is configured to make the voltage applied to the pump cell a voltage of a starting voltage of decomposition of water or more when the estimated temperature of the pump cell estimated by the temperature estimation part is within a predetermined temperature region of less than an activation temperature of the pump cell as control suppressing evaporation.

Various embodiments disclose an electronic circuit for an electrochemical gas sensor. The electronic circuit comprises a first switching element electrically coupled to a reference terminal of the electrochemical gas sensor and a ground voltage terminal. Further, the electronic circuit comprises a second switching element electrically coupled to a sensing terminal of the electrochemical gas sensor and the ground voltage terminal. In an instance in which the electrochemical gas sensor is powered OFF, the first switching element and the second switching element are configured to electrically couple the reference terminal and the sensing terminal to the ground voltage terminal such that current generated when the sensing electrode and the target gas react while the electrochemical gas sensor is powered OFF flows to the ground voltage terminal and the potential of the reference terminal and the sensing terminal remain the equal.

An NOx sensor includes a gas sensor element, a body member made of metal, and a protector made of metal. The body member is formed into a tubular shape extending in an axial direction and accommodates a gas sensor element internally of the same. The NOx sensor is formed into a tubular shape extending in the axial direction and includes an attachment member disposed such that a space extending in the axial direction is formed between the attachment member and the body member. The gas sensor element includes an oxygen concentration detection cell having an oxygen ion-conductive solid electrolyte layer and a detection electrode and a reference electrode formed on the solid electrolyte layer and forming a pair, and a heater for heating the oxygen concentration detection cell to a predetermined temperature. The oxygen concentration detection cell is disposed in the space.