Carter Reservoir Analyzer Timing Circuit

The timing circuit generally employed in Carter Reservoir Behavior Analyzersconsists of a synchronous motor driven cam which actuates a microswitch. Amechanically actuated timer of this type has several inherent disadvantages, among which are the following:The first time interval may not be of uniform length, depending on the exactposition of the cam at the conclusion of a previous run.The positioning adjustments on the microswitch lever arms are critical andrequire periodic readjustment.The mechanical system is subject to wear which will ultimately impair itsaccuracy. It was therefore considered desirable to devise an alternate method which wouldeliminate these difficulties without introducing others that would be equallytroublesome. This note describes the design of an electronic timing devicewhich has been incorporated in the analyzer constructed by the Field ResearchLaboratories of Magnolia Petroleum Co. The electronic timer circuit is built around a simple neon glow tube relaxationoscillator, the complete circuit diagram of which is shown in Fig. 1. Theoperation of the circuit is as follows: Condenser C1 is charged to the criticalfiring voltage of the neon glow tube VR-75 by battery B, through resistors R1and R2. When the neon glow tube fires, the condenser C1 is discharged. T.N. 63