Abstract: A method and an apparatus for calibrating a dissolved oxygen analyzer are disclosed. In the method, a zero point is first determined and set on the analyzer by filling into the analyzer a saturated aqueous solution of an oxidizer that contains 0 ppb oxygen. A span point is then set on the analyzer by filling a sample solution in the analyzer and flowing a cell current through a Faraday electrode until a 20 ppb oxygen is produced and then setting the point as a span point for completing a two-point calibration process. A slope for calibration can be obtained between the zero point and the span point.

Abstract: In order to correct the characteristic of a linear lambda probe which is arranged in an emission control system of an internal combustion engine upstream of a catalytic converter, in an overrun fuel cut-off phase the throttle valve and/or at least one gas exchange valve of the internal combustion engine is opened, and the signal of the lambda probe is assigned to the lambda value corresponding to the oxygen concentration of the ambient air. It is then possible, together with a conventional trimming controller which corrects the assignment of the signal to lambda=1, to correct the gradient of the characteristic.

Abstract: A control device for an air-fuel ratio sensor for detecting, from an oxygen concentration detecting device, a current corresponding to a concentration of oxygen contained in a gas by applying a voltage to the oxygen concentration detecting device. The control device detects an alternating impedance of the oxygen concentration detecting device corresponding to each frequency by applying alternating voltages of a plurality of frequencies to the oxygen concentration detecting device and analyzing each of the alternating impedances detected by the impedance detecting means so as to calculate a parameter indicating a change in the characteristic of the oxygen concentration detecting device, and thereby achieve control of the air-fuel ratio sensor.

Abstract: A respiratory function monitoring device comprising a flow sensor and a conversion device is herein disclosed. Also disclosed are structures for carrying out an auto-zero calibration, a purging function, and temperature compensation. Methods for implementing the auto-zero calibration, the purge function, and the temperature compensation are also disclosed.

Abstract: An apparatus and method for diagnosing the condition of a sensor in an internal combustion engine upstream from the catalytic converter. The diagnosis utilizes a signal from a second non-linear probe downstream from the catalytic converter. This signal is processed to give a signal that is filtered. The filtered signal is in turn compared with maximum and minimum values. The upstream probe is considered to be correct if the signal falls between these two values or faulty if it falls outside the values.