Abstract: A gas monitor for monitoring the concentration of particular atmospheric constituent includes a sensor and a signal processor that provides concentration-indicating output signals in response to successive samples admitted to the sensor. The processor multiplies the sensor signals by a calibration signal. It automatically recalibrates the monitor by periodically causing a sample having a standard concentration to be admitted to the sensor and adjusting the calibration signal to provide a corresponding predetermined output signal level.

Abstract: A frequency transducer circuit for providing a precisely adjusted range of output currents characterized by the combination of a diode pump circuit with a low impedance input circuit including a control transistor with a first variable impedance for determining the upper limit of the output range, and a biasing circuit with a second variable impedance for adjusting the lower limit of the output range.Calibration of the output current range is facilitated in one preferred embodiment of the invention by eliminating interaction between the upper and lower range limit adjustments.

Abstract: A probe assembly for use with an electrical voltmeter-ammeter, to adapt the meter to read electrical resistance, is provided with a pair of probe electrodes connected respectively to separate, flexible, insulated electrical conductors that are coupled to a common multi-terminal plug housing. Terminals mounted in the plug housing are arranged to cooperate with a plurality of terminals mounted on a terminal board in a meter. The probe assembly is further characterized by incorporating a fuse and a battery electrically connected in series with one of the probe electrodes and the terminal to which it is connected by a flexible conductor. A potentiometer is connected in series with one of the flexible conductors while a resistor connected between the flexible conductors to enable a meter to be adjusted for full scale deflection when it is connected to the probe assembly while the probe electrodes are in engagement with one another.