convert resistive sensors output to 0 - 5V??

S

settra

Member

• Nov 20, 2015

• #1

Hello forum. I have a resistive sensor, with output from 40ohm to 280ohm.

What i want to do is add some circuity to convert this output, to 0-5Volts. from what i can find, there is no way to do it using single-stage op-amp or just a resistor.. (best i can get is 1.5v to 4v) .so i suppose it will require a two stage op-amp or something...

can someone provide me with a circuit that will do this??

thanks!

 

alec_t

Well-Known Member

Most Helpful Member

• Nov 20, 2015

• #2

Is the resistor volt-less (floating), or does it have one end fixed at 0V (ground), or .......?

 

S

settra

Member

• Nov 21, 2015

• #3

The resistor is completely unconnected. just to wires. it might as well be a simple potentiometer

 

MikeMl

Well-Known Member

Most Helpful Member

• Nov 21, 2015

• #4

What supply voltage(s) do you have available? How well regulated are they?

If this is an Arduino project, do you have a more positive voltage than 5.0V available?

 

S

settra

Member

• Nov 21, 2015

• #5

It will be used in car enviroment. so it will be very noisy... i was thinking about using 5v as input. BUT, input regulation is not such a big probelm... the sensor itself will already have too much noise in the readings (fuel tank sender)
But nevertheless the output should be 0-5v!!

(p,s of course all circuity will be outside of the tank )

 

Ian Rogers

User Extraordinaire

Forum Supporter

Most Helpful Member

• Nov 21, 2015

• #6

You can do it with a rail to rail op amp and 6 resistors...

 

S

settra

Member

• Nov 21, 2015

• #7

How ?

 

Ian Rogers

User Extraordinaire

Forum Supporter

Most Helpful Member

• Nov 21, 2015

• #8

280 ohm output


40 ohm output

 

Attachments

• 40 ohm.jpg

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S

settra

Member

• Nov 21, 2015

• #9

nice!! thanks allot man! the resistos R6 R7, are both 1k ??

 

Ian Rogers

User Extraordinaire

Forum Supporter

Most Helpful Member

• Nov 21, 2015

• #10

Yep

Edit.... You may want to put a preset where the 62 ohms is and a preset where the 5k2 is..
That way you can calibrate it...

 

S

settra

Member

• Nov 21, 2015

• #11

cool ! thanks allot m8! this seems to be exactly what i was looking for!

 

MikeMl

Well-Known Member

Most Helpful Member

• Nov 21, 2015

• #12

Modern Rail-to-rail OpAmp.
There is some combination of R1, R2 and R3 that perfectly fits the end points.
I included a slosh-filter (R5-C1).
Power supply filtering not shown...
Circuit is ratiometric with respect to the 5.00V source.