Hi Trent,
Here is a circuit which was published in a magazine back in 1994.
The circuit was connected to the serial port of a PC via a parallel
to serial interface circuit. A MS-DOS program (see picture) was
used to display the measured resistance value and show the color
code of the measured resistor.
10mA was used for resistors from 1 to 100 ohm.
1mA was used for resistors from 100 to 1k ohm.
100µA was used for resistors from 1k to 10k ohm.
10µA was used for resistors from 10k to 100k ohm.
1µA was used for resistors from 100k to 1 Mega ohm.
TS27M2CN datasheet:
http://www.st.com/stonline/books/pdf/docs/2306.pdf
LM334 datasheet:
http://www.national.com/ds/LM/LM134.pdf
Here is the schematic. (I have added the values).
(Click to enlarge)
How the current source is used:
(Click to enlarge)
The DOS program:
(Click to enlarge)
Best regards,
Luciano
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