Is My Pull Up Resistor Calculation Correct?

AI Thread Summary
The discussion revolves around the calculation of resistance using a pull-up resistor and a current source. The user initially calculates a current of 0.0006A, expecting a voltage drop close to 5V, but instead measures 9.83V. This discrepancy leads to a calculated resistance of approximately 16.4k ohms, which the user doubts. A response highlights that the current source may not be precise, noting that real-world current sources require a minimum voltage drop to function correctly. The conversation emphasizes the importance of understanding the operational characteristics of current sources in circuit calculations.
ee1215
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http://i.imgur.com/TbYIHnb.png?1

So, if I have a pull up and apply a current source. How would I need to read/calculate resistance?

V=IR
I = 5V/8k = .0006A would result in a voltage drop of close to 5V

Using a current source/Voltage reader I supply .0006A which should equate to ~5V drop

But when I read my voltage reader I get 9.83V. Is this correct?

Then my resistance would be 9.83/.0006 ~ 16.4k ?

These calculations do not seem correct.
 
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ee1215 said:
http://i.imgur.com/TbYIHnb.png?1

So, if I have a pull up and apply a current source. How would I need to read/calculate resistance?

V=IR
I = 5V/8k = .0006A would result in a voltage drop of close to 5V

Using a current source/Voltage reader I supply .0006A which should equate to ~5V drop

But when I read my voltage reader I get 9.83V. Is this correct?

Then my resistance would be 9.83/.0006 ~ 16.4k ?

These calculations do not seem correct.

Sounds like your current source is not very precise. Keep in mind that real-world current sources need to have some voltage drop across them in order to operate correctly. Typically you need a couple of volts across a current source in order for it to say "in compliance".
 

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