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I have a speed sensor (pitot tube) that operates as described in the figure below.

My problem is that the resolution of the sensor is not good when read by the Arduino UNO ADC (around 2.75m/s.)

My solution would be, as we don't work with negative pressures, to offset the whole signal by -2.5V so it only reads positive pressures, then amplify by a 2x factor so we cover the whole 0-5V spectrum of the Arduino, and try to protect the Arduino from the negative voltages that may arise for some reason.

Keep in mind that it's an embedded application.

Do you guys think this is a valid idea, do you have any other solution? How could I implement it? I just started as an intern.

Output versus Pressure Differential

JRE
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Ricardo Silvestre
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1 Answers1

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It's basic signal conditioning, it's done all the time. A pair of low offset opamps will solve the issue: one stage to subtract 2.5 (a differential stage) and one for a ×2 gain. If you study the theory you could do it with one single stage, depending on your supply and your effective common mode range.

There are more performant solutions (like stabilized zero drift amps or specialized signal conditioner) but given your transducer is 6.25% I don't think they would be warranted.

Depending on your parts (tolerances and so on) you'll maybe need some calibration, in software (otherwise it's usually simpler to acquire precision parts than using trimmers and such)

EDIT: be careful around the zero, your sensor tolerance could map a zero pressure to a value slightly lower to 2.5 so subtracting 2.5 will lead to lose the lower end of your range. Also even rail to rail amps often simply work better away from the rails (it depends on the architecture, the details are in the datasheet)

Lorenzo Marcantonio
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