Ratiometic_conversion

Published:2009/7/25 4:32:00 Author:Jessie | From:SeekIC

Figure 9-4 shows the ADC0816/17 connected for ratiometric conversion. Becauseboth ends of the 256R resistor ladder are available externally (Fig.9-1) the ICs areideally suited for use with ratiometric transducers A ratiometric transducer is aconverslon device in which the output is proportional to so me arbitrary full-scalevalue．The actual value of the transducer output is of no great importance but theratio of this output to the full-scale reference is valuable．The prime advantage of a ratiometric transducer is that an accurate reference is not essential However the reference should be nolse free because the voltage spikes during a converslon could cause inaccurate results.The circuit of Fig．9-4 uses the existing 5-V supply for reference thus eliminating the need for a special external reference. Take careto reduce power-supply nolse，The supply lines should be bypassed and separate PC traces shodld be used to route the 5-V and ground to the reference inputs andto the supply pms (if practical). NATIONAL SEMICONDUCTOR APPLICATION NOTE258 1994. P.592．



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