Vdivide resistor sizes
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Posts: 46,084
I was wondering if someone would advise me?
For a divider to get input to an opamp/adc:
Dividing 12V,
R1=100K, R2=10K = 100 microamps consumption
R1=1.0M, R2=100K = 10 microamps consumption
Resistor cost is esentially the same.
Is there a downside to the higher value resistors?
Chuck H.
For a divider to get input to an opamp/adc:
Dividing 12V,
R1=100K, R2=10K = 100 microamps consumption
R1=1.0M, R2=100K = 10 microamps consumption
Resistor cost is esentially the same.
Is there a downside to the higher value resistors?
Chuck H.
Comments
higher values may produce greater error than 5% of the lower values.
Remember that one resistor may be high in value and one the opposite. Also,
in general, higher values may make the circuit more suseptable to noise.
Ideally, the circuit should represent a match to the driving circuit.
jim
http://www.geocities.com/jimforkin2003
Original Message
From: chuck_33708 [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=U8fN6tn8UAL0jw-a5hyQ-J8_xnnxvC2CuUmeBBiN9ixD_cCgGk5nkb94b0hzU5-EYgFwU4nxSQ]ch12@n...[/url
Sent: Thursday, May 01, 2003 3:40 PM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] Vdivide resistor sizes
I was wondering if someone would advise me?
For a divider to get input to an opamp/adc:
Dividing 12V,
R1=100K, R2=10K = 100 microamps consumption
R1=1.0M, R2=100K = 10 microamps consumption
Resistor cost is esentially the same.
Is there a downside to the higher value resistors?
Chuck H.
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>I was wondering if someone would advise me?
>For a divider to get input to an opamp/adc:
>Dividing 12V,
>R1=100K, R2=10K = 100 microamps consumption
>R1=1.0M, R2=100K = 10 microamps consumption
>Resistor cost is esentially the same.
>Is there a downside to the higher value resistors?
>
>Chuck H.
The downside is:
Since the input to an ADC can often be viewed as a capacitor,
you essentially create a low-pass filter. Depending on your
application, this may or may not be desirable. Also with
a higher resistance at the input, you are more susceptible to
external electrical noise coupling.
Generally:
higher resistor values = slower response and increased noise