unstable output MPX53

hellow, i have problem with my mpx53 pressure sesor output. why my sensor output unstable? i connect sensor output to A7 and use internal 3,3v from arduino. thx.

Need to see a wiring diagram and the program that produced that output.

my attach program,

and my wiring, Sensor MPX ---- Instrumen Amplifier INA125 — Arduino A7, 3,3V and Ground
thx

sketch_apr19a.ino (509 Bytes)

How did you connect the sensor to the INA125. Did you power the sensor from the INA125's Vref (you should). How did you power the INA125. What is the value of Rg. Post a (hand drawn) circuit diagram. Leo..

Wawa:
How did you connect the sensor to the INA125.
Did you power the sensor from the INA125’s Vref (you should).
How did you power the INA125.
What is the value of Rg.
Post a (hand drawn) circuit diagram.
Leo…

i am sorry, i use INA121, value Rg i use 10 ohm,
my circuit diagram

Several problems. You supply the sensor from a (resonably) stable 3.3volt. And probably measure with an potentially unstable Aref (5volt). Better to power and measure from the same source. Google "ratiometric".

The output of the INA121 could swing from ~0.15volt to ~11.1volt on a 12volt supply. The Arduino shouldn't see more than 5volt on the analogue input. You could fry the pin. You need a voltage divider on the output of the INA to bring ~11volt down to ~5volt.

In the end it would be easier to dump the sensor, and buy one with inbuild instrumentation amp and temp compensation. Look through the extensive list of amplified MPX sensors. Leo..

If you can feed the 3.3V into AREF and use analogReference (EXTERNAL); you will get ratiometric result. I wouldn't use a voltage divider from the INA121, its dumb to amplify and then attenuate again, just use a 10k resistor on the output of the amp so it cannot damage the Arduino pin should it go out of range.

Be careful in your ground wiring not to get a ground loop, that will inject noise into you readings, follow a star ground scheme (especially if anything high current is running off the same Arduino)

You could supply the INA121 from 5volt if 3.3volt Aref is used. Leo