Processor-Controlled Microdensitometry

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Abstract
A new scheme of densitometric data collection is described which comprises a digital filtering technique and process control program. A 6502-based PET 2001/32K microcomputer and an Elscan model 2500 specular microdensitometer are interfaced through the standard 6522 VIA port chip. An Analog Devices ADC80/12 monolithic A/D converter is used to digitize the analog output of the light photometering system. Additionally, control of the optical scanner assembly is provided through processor-driven 4-phase TTL logic circuitry. The technique applies to any analog signal of interest, either for filtering purposes or for recording directly into memory for later waveform or transient analysis. The maximum data gathering rate is 40 kHz, limited by the A/D conversion time of 25 μs.