Building a Voltmeter, need IC datasheet help

AI Thread Summary
The discussion focuses on building an autoranging digital voltmeter using the ICL7107 chip, with specific questions about the Vref inputs and the configuration of the RefHI and RefLO pins. The user seeks clarification on whether Vref should be set 1V above the low input or relative to ground, and inquires about the use of a potentiometer instead of resistors in the schematic. Additionally, there is uncertainty about connecting the COM pin to the low input and how it operates based on the datasheet's explanations. A member notes that this question has already been addressed in another forum, providing a link for further reference. The conversation highlights the complexities of interpreting IC datasheets for practical applications.
kjnhu
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I am building an autoranging digital voltmeter as the subject line suggests and am having a problem with the ICL7107 chip that I am using. Looking at figure 15 on: http://www.intersil.com/data/fn/fn3082.pdf
specifically RefHI and RefLO, with a 2V max input difference between the pos and neg inputs. I do not necessarily have the negative input at 0 volts, and therefore would like assistance on how to use the Vref inputs. Do I need to set Vref=1V greater than the low input, or should it be 1V with repect to ground? Also why does the figure show a potentiometer rather than simply using resistors? Also should I just short the COM pin to my low input? I am unsure of how it actually functions after reading the cryptic explanation on the data sheet. Thank you for your assistance.
Kevin Hurley
 
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