Abstract: A dissolved oxygen analyzer which includes a sensor having a lead electrode and lead wire extending therefrom and a silver electrode and silver wire extending therefrom. The electrodes are immersed in an electrolyte and both metals are substantially pure. The silver electrode is positioned in adjoining relationship to an oxygen permeable membrane immersed in a sample water stream being tested. The sensor further includes a pressure equalizing diaphragm in communication with the sample water to maintain uniformity of pressure in the sensor with that of the water and a constant head tank maintains uniform water pressure and a thermistor monitors the water temperature and modifies the output of an amplifier connected to said wires to compensate for temperature changes.

Abstract: A detector for reducing and oxidizing agents carried by fluids which detector includes an elongated exposed porous member having an opening extending therethrough, an electrolyte gel containing a metal salt filling said opening, a first metal electrode extending through said gel and a metal electrode on the outer side of said porous member, the porous member and electrode upon being placed in the path of the fluid will cause a current to be developed between the electrodes which is proportional to the amount of chemical in said fluid. The detector is especially useful for the detection of hydrazine in boiler feed water.

Abstract: Filtering means for biophysical recording apparatus for removing interference from a signal source which includes a band rejection or notch filter and means for inserting the filter into the signal circuit when the signals have a certain characteristic and for removing the filter when the signals have another characteristic.

Abstract: Apparatus for generating a feedback signal for effecting rotation of a servo motor precisely in accordance with changes in the input signal and which includes a first annular coil and two angularly positioned coils inductively coupled with the first coil. An alternating current signal is fed to the first coil and the voltages induced into the angularly positioned coils are rectified and subtracted to produce the feedback signal. Variations in the feedback signal are effected by mechanically coupling the shaft of the servo motor with said coils to produce rotation of the first coil relative to said angularly positioned coils. An electronic network is provided to effect rectification and subtraction of the induced AC signals and a corrective network may be included for additional accuracy, if desired.

Abstract: Electrocardiographic apparatus wherein said apparatus is contained within a wholly insulated enclosure and the recording assembly including writing pens is provided with means for placing an insulating barrier in a position to protect the pens when replenishing the recording paper.