電圧-周波数変換器を用いるオンラインA/D変換の精度向上

概要

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A simple and new method of high precision on-line A/D conversion was performed using a voltage-frequency converter. The analog outputs of instruments are first converted into frequencies followed by counting serialization and finally data aqauisition by minicomputer. The voltage-frequency converter was made using IC circuits of Teledyne-Philbrick Model 4709-03 and Texas Instrument-SN74XX. AIso, a serializer was made from TI Model SN74XX series and NE555. This serializer is also used for the timing of data transfer. A preamplifier was made using a TP Model 1035-02 (Input impedance was found to be 10^<13>ohm). A frequency counter used was of a YHP 5326B. A computer system used was a PDP 11/10 of 16k core memory with a high speed paper tape reader, puncher, teleprinter, and a digital I/O. Assembler languages were used for all of the software programming. The method of voltage-frequency conversion in this case is advantageous for the following two reasons: i) The precision of analog-to-digital conversion is increased by 1.5 significant digits as compared with that using a conventional 12 bit-A/D converter, ii) Noise immunity is more effective. As an illustrative example, the emf of ion-selective electrodes was measured by an on-line computer with precision and resolution of five significant digits and 10 micro volts, respectively, taking a copper electrode in 1mM Cu(II) ion.
社団法人日本分析化学会の論文
1978-03-05