opamp amplifications and pressure sensor

Discussion in 'The Projects Forum' started by krishnachaitanya, Mar 12, 2015.

  1. krishnachaitanya

    Thread Starter New Member

    Mar 5, 2015
    Im using a px26 001GV differential pressure sensor for a project with arduino, here is the data sheet. (http://www.omega.com/manuals/manualpdf/M1608.pdf) Now, I have few questions regarding this.

    1) I'm using this around a valve to know the differential pressure, lets say side A and side B Now if side A>B i get a positive voltage in milli volts, what if side B>A would it give a negative voltage? so would I get a range of voltages for its full functionality from negative to positive like say -8mv to +8mv?

    2)I'm using an op amp to amplify the reading so I could amplify 8.6mv to 1.8V and then the opamp saturates, is there any way around this?

    3) the opamp AD620AN which is a instrumental amp to be precise , needs voltage ranges -5 t0 +5 so i used a 10 volts dc, made a voltage divider, created a virtual ground. So what if I connect this system to arduino (0to5V range) would the divider cut off the system to (-2.5 to +2.5)?If so, should I check my circuit by using a 5V Dc and using the divider and check how the opamp responds?

    PS: I'm new to this , please try to avoid all the electrical lingo, I wouldn't understand it. Thank you for your effort!
  2. AnalogKid

    Distinguished Member

    Aug 1, 2013
    1. This is a positive pressure only device. It is powered from a single 10V source, not bipolar supplies. Because of this, it's output is unipolar only. The data sheet doesn't say, but I think it is safe to assume that negative pressure gives 0 V output. Here is a little more information: http://sensing.honeywell.com/index.php?ci_id=49847

    http://cache.freescale.com/files/se...ORMAT=pdf&WT_ASSET=Documentation&fileExt=.pdf - Figure 2 has a version of what you are doing. This uses two separate opamps in an instrumentation amp configuration.

    2. Yes. Your virtual ground isn't working the way you think it is. Your schematic shows two 10V supplies. Can these be connected together to form a +/-10V supply with a true ground in the middle?

    3. If the two supplies are connected together in series, then the center point is your system ground, and connects the Arduino ground. The sensor runs off the +10V, the AD620 runs off both the +10V and the -10V. In this way the output of the 620 can swing to 0V for a 0V input.

  3. krishnachaitanya

    Thread Starter New Member

    Mar 5, 2015
    upload_2015-3-17_15-43-8.jpeg It works i guess, im able to amplify and read the values