Computer analog-to-digital converter

Fig. 1 Scheme of the OCT system. SLD—superluminescent diode FBS—fiber-optic beam splitter M—mirror L—lenses S—sample PD—photo-diode F—band-pass filter A— logarithmic amplifier AD—amplitude detector ADC—analog-to-digital converter PC— computer. 

Both gas chromatographic instruments were connected with a PDP 11/45 computer via an analog-to-digital converter. The peak areas were calculated from the digitalized chromatographic data by means of software developed at Delft University of Technology. 

Interface. The interface includes a 10-bit analog-to-digital converter, a ten-channel multiplexer, and eight contact sense lines. The converter will operate at rates up to 20,000 conversions per second with a precision of 1/1000 for analog inputs with either 10 or 100 mv full scale values. The contact sense lines are used to communicate elution dumps and sample injections by signaling the computer on a circuit closure. The interface, with eight contact sense lines and four active A/D channels, is capable of handling data from four GPC instruments simultaneously. 

The second hardware unit was an interrupt, skip-check control unit for the Reticon arrays. This unit allows the computer to see the end-of-scan and beginning-of-scan pulses generated by the arrays and allows the computer to have an on/off control of the external clock which is used to start the analog to digital converter. 

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