Computerized Oxygen and Carbon Dioxide Detector

The purpose of the experiment is to measure the oxygen and carbon dioxide content of the earth\´s atmosphere to determine if there is a decrease or increase with the passing of time (years). This newly developed data acquisition and manipulation system operates as follows: Measurement is accomplished by placing two samples of air in the path of an argon laser. The light particles emitted from the samples are transmitted to two photomultiplier tubes (PMTs A and B) through a set of mirrors and a focusing arrangement. There is a mechanical shutter-wheel placed in front of the PMTs to alternate the unknown and standard light particles proceeding to the PMTs. The outputs of the PMTs are shaped to a fast NIM standard signal and applied to a CAMAC 12 channel, 100 MHz scaler (A to channel 0, B to channel 1). An eight millisecond gate is used to enable the A and B detectors. The position of the shutter-wheel is determined by synrhronization pulses scribed on the wheel. The "1" sync pulse represents the unknown data while the "2" sync pulse is the standard data. The two Sync pulses are applied to a Quad Counting Register (channel 0). A Gate pulse is applied to channel 1 of the Quad Register to represent the number of actual A and B (unknown/standard) pairs of data presented to the Data Acquisition System. An Inhibit signal is used to sync the LSI-11/2 computer to obtain the Sync, A and B Data, and Gate signals.