This is a pretty primitive question, but I need to confirm this.
I have a sensor output with specs that say 2ma max into a minimum 2K load.
I want to run this output through a variable pot and then a fixed resistor to ground, and take the output of the pot wiper as the input to a picaxe 08M, taking into consideration the input impedance requirement of the 08M.
The basic circuit is below (if my formatting survives).
Question is this: How do I figure the input impedance in this scenario? Given the input impedance requirement of the 08M, what are the largest values I can safely use for R1 and R2, given R1 is roughly 1/10 the value of R2? Are 1K and 9K reasonable values here, or can I go with 10K and 90K? I'd like the higher values, if they will not affect the readADC10 accuracy.
Help greatly appreciated.
<code><pre><font size=2 face='Courier'>
sensor output
-------|
\
/
R1 \<------ 08M input
/
|
\
R2 /
\
/
|
GND
</font></pre></code>
I have a sensor output with specs that say 2ma max into a minimum 2K load.
I want to run this output through a variable pot and then a fixed resistor to ground, and take the output of the pot wiper as the input to a picaxe 08M, taking into consideration the input impedance requirement of the 08M.
The basic circuit is below (if my formatting survives).
Question is this: How do I figure the input impedance in this scenario? Given the input impedance requirement of the 08M, what are the largest values I can safely use for R1 and R2, given R1 is roughly 1/10 the value of R2? Are 1K and 9K reasonable values here, or can I go with 10K and 90K? I'd like the higher values, if they will not affect the readADC10 accuracy.
Help greatly appreciated.
<code><pre><font size=2 face='Courier'>
sensor output
-------|
\
/
R1 \<------ 08M input
/
|
\
R2 /
\
/
|
GND
</font></pre></code>