I'm trying to measure water pressure of water pipe by exactly replicating this : http://www.practicalarduino.com/projects/water-tank-depth-sensor

When I tested the sensor (by leaving both inlet free, and printed the result directly to Arduino's Serial), I got a wave-like output. The sensor gave high output (1023) then steadily dropped to 0, and then increased again.

I've also tried to test the sensor by directing both output (+Vout and -Vout) to Arduino's analog pin. And the result stayed the same.

My question is: Is this condition normal? I have no experience before with pressure sensor so I have no idea if this is working correctly or not.

PS: I've tried the component by using 9V adaptor. From the datasheet (http://www.nxp.com/files/sensors/doc/data_sheet/MPX2010.pdf) I found that

Vs = 10 Vdc

While Vs = supply voltage, what does Vdc stands for? And what's the difference it has with Vs?

Update : I found this https://stackoverflow.com/questions/2851078/analog-readings-on-arduino-returns-wrong-values and it seems the case is almost similar to me. Should I do the same with my MPX2010 from the output pin (even though MPX2010 already had its own ground from the 1st pin)?

  • \$\begingroup\$ Waves and water go together but without your result being calibrated against some other measurement device who can tell. \$\endgroup\$
    – Andy aka
    Commented Jul 21, 2016 at 15:00
  • \$\begingroup\$ 'Vs' is a label for one of the test parameters. In this case, 'Vs' identifies the voltage value applied to the power supply pins on the device under test (the MPX2010 sensor). 'Vdc' means "Volts direct current" versus 'Vac' which is "Volts alternating current". This SparkFun webpage describes the differences between direct current and alternating current. \$\endgroup\$ Commented Jul 21, 2016 at 20:35
  • \$\begingroup\$ @JimFischer I understand what DC means. What still bugged me is those 'Vs=10Vdc'. Is it read "Vs equals 10 times Vdc" or other meaning? \$\endgroup\$ Commented Jul 22, 2016 at 3:46
  • \$\begingroup\$ VDC is units, like meters or liters or dogs. 10 meters. 10 liters. 10 dogs. 10 volts dc. \$\endgroup\$ Commented Jul 22, 2016 at 4:53
  • \$\begingroup\$ You can read "Vs=10VDC" as "(positive) supply voltage = 10 V DC (with respect to ground)". \$\endgroup\$
    – Transistor
    Commented Jul 23, 2016 at 15:31

1 Answer 1

  • You have a design.
  • You have built a circuit.
  • You have written some code.
  • You are now in the test debug phase.

When things don't work out you need to isolate the area of the fault. In this case there is a convenient point at the analog input to the micro.

  • Use your multimeter to check the voltage from the pressure sensor amplifier.

  • If multimeter reads stable voltage:

    -If it is stable and not stuck at zero or max supply voltage then your micro should give out a fairly stead reading on the serial port.

    • Check your code.
    • Try wiring a potentiometer to the analog in and apply a steady voltage. Debug the micro and code this way.
  • If multimeter reading is unstable:

    • Problem somewhere in the amplifier.
      • Check each opamp output.
      • Check the transducer output.

Report back with your findings.

  • \$\begingroup\$ I have checked the sensor using multimeter during activated. And it produced stable reading \$\endgroup\$ Commented Jul 23, 2016 at 15:17

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