DATA_ACQUISITION_SYSTEM_I

Published:2009/7/10 3:07:00 Author:May | From:SeekIC

The Hl-506 multiplexer is used as an analog input selector, controlled by a binary counter to address the appropriate channel. The HA-5330 is a high-speed sample and hold. The sample/hold control is tied to the status (STS) output of the HI-774A; whenever a conversion is in process, the S/H is in the hold mode. A conversion is initiated when the clock input becomes low; when the clock becomes high, the mux address changes. The mux will be acquiring the next channel while the ADO is converting the present input, held by the SiH. The clock low time should be between 225 ns and 6.5 ps, with the period greater than 8.5 μs. With this timing, T/C will be high at the end of a conversion, so the output data will be valid ~ 100 ns before STS goes low. This allows STS to clock the data into the storage register. The register address will be offset by one; if this is a problem, a 4-bit latch can be added to the input of the storage register. With a 100-kHz clock rate, each channel will be read every 160 μs.



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