Design and Construction of Low Cost Electronic Digital Integrator for Gas Chromatography

Abstract

A simple digital integrator for gas chromatography was designed, and details on the performance and the electrical circuits of the unit are described. The voltage output from gas chromatograph was invertedly amplified by 100 times using μA-741 type operational amplifier, then fed into the charge-balancing type voltage-frequency converter and the output pulse train was counted by integrated circuits (SN 7490 N) and displayed by 5 digit Nixie tubes. As valley senser type peak detector was also attached to the integrator, the display could be read from the memory of the integrals of the former peak, after recognition of the next peak elution. On memorizing integrals of the former one by hand and by means of push button switch operation, the display could be read from the counter, as pules train was counted. The circuit diagrams are shown in Figs. 2, 3, 4, and the linearity evaluation data of the voltage-frequency converter are shown in Table 1. As for the gas chromatographic analysis, the precision and reproducibility of the individual measurement were good, as shown in Table 2 and the cost of construction of the unit was about 1/20 that of the commercial one. © 1974, The Chemical Society of Japan. All rights reserved.