# voltage scaling

Discussion in 'Electronic Basics' started by [email protected], Nov 2, 2006.

1. ### Guest

I am using an analog sensor and would like to scale the output voltage
down prior to recording the value. I am running into problems
acheiving this, however. I have tried a simple voltage divider circuit
but the current from the sensor output is so minute it does not
function properly. Does anyone have any suggestions on how to scale
voltage with very little current? Thank you,

Evan

2. ### Jonathan KirwanGuest

Without all the details, a design isn't possible. But an opamp is a
very common approach to this.

Jon

3. ### BaronGuest

If the resistance of your voltage divider dragging too much current then
raise it ! Try a value 10 times higher !

4. ### Jonathan KirwanGuest

Problem is, we don't know what the OP is hooking up to the divider to
monitor the voltage and how it loads it.

Jon

5. ### BaronGuest

Thats why I suggested it that way ! Don't 10M DMM's come in handy !

6. ### SkepticGuest

The more details you provide the better the answers you will receive. What
is the voltage and current the sensor provides. Better yet, what is the
sensor and what is it measuring?

7. ### Homer J SimpsonGuest

If this is a pH sensor, say, you need to design the input circuit correctly.

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8. ### Guest

The sensor is a MEMS biaxial accelerometer I am using to measure tilt.
I am suppling 3V, the output voltage range is 1.25 V +/- 0.1 V and the
current is less than 0.01 mV (I calculated it to be aprox 0.005 mV).
Thanks

9. ### redbellyGuest

Current is measured in mA, not mV. Please clarify, are you talking
about the output voltage or current? Also, what resistance did you use
for the voltage divider?

Mark

10. ### Guest

Output voltage: 1.25 V
output current: .005 mA

I used a 150 and 220 kOhm resistors.

11. ### redbellyGuest

their output is essentially a voltage source. The output current just
depends on what resistance is tied to the output.

I don't know what you're using to read the signal. If you're looking
at the output on an oscilloscope, that's typically a 1 M-ohm load and
that will alter the reading on a several-hundred kOhm divider. On the
other hand, a 10 M-ohm multimeter should have very little affect on the