Low Voltage RCtime

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I need to measure a voltage range of 0 to 45 mV using BS2's RCtime
command. What is the resolution on such low voltage? Should I
amplify the signal? How do I do that linearly?


Al Najjar

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>I need to measure a voltage range of 0 to 45 mV using BS2's RCtime
>command. What is the resolution on such low voltage? Should I
>amplify the signal? How do I do that linearly?
>
>Al Najjar

Hi Al,
It can be done, but you need an op-amp circuit to convert the small
voltage to a current. (VCCS: voltage controlled current sink) The
resolution of the RCtime command is around 10 bits. Here is some
information:

http://www.emesys.com/BS2rct.htm#SmallV

The resistor R1 could be 1kohm to convert 0.1-45 millivolts to 0.1-45
microamps, and C1=0.01uf. That will give an RCtime count of about
145 when the input is 45 millivolts and 65535 when the input is about
0.1 millivolts. The RCtime value is inversely proportional to the
input voltage, and the response does not go all the way to zero with
the circuit as shown.

Do you have a particular reason you want to use RCtime instead of an
A/D converter?


-- best regards
Tracy Allen
electronically monitored ecosystems
http://www.emesystems.com
mailto:tracy@e...