Pressure Transducer (PX-137-015DV) with Grove Diff. Amplifier v1.2 - Signal is jumpy

Discussion in 'The Projects Forum' started by Lucyfur1, Sep 20, 2016.

  1. Lucyfur1

    Thread Starter New Member

    Jul 16, 2015
    Hello AAC. I appreciate your time and help.

    I am trying to use a pressure transducer (PX-137-015) with my Arduino Mega. My first mistake was brushing over the fact that the transducer's output is 90 mV - I thought that was in the range of the Arduino but of course it's too small. I tried connecting the transducer outputs (it is a differential sensor) to A0 and A1, then finding the difference using analogRead() and basic math, but like I said, the signal is too small for the Arduino to read.

    When I used a multimeter attached to the V+/V- pins of the transducer, it was able to read ~3.5 mV when I blew into the "high" port. So I know that the transducer is working. I am trying to use the Grove Differential Amplifier v1.2 with gain of 35 but the signal is sporadic! Here is the link :

    My connections are as follow:

    J3 side:
    VCC -> 3.3V
    GND -> GND
    V+ -> high side of transducer
    V- -> negative side of transducer

    J4 (white terminal) side:
    GND -> GND
    VCC -> 3.3V
    NC -> no connection (?)
    SIG -> A8

    My code is:

    void setup() {
    // put your setup code here, to run once:
    analogReference(EXTERNAL); //connected to 3.3V source on board

    void loop() {
    // put your main code here, to run repeatedly:
    float pressure = analogRead(A8) * (3.3 / 1023.0) ;


    The serial port will display -0.00 but won't show anything when I apply some pressure to the high side port (even though the multimeter reads 3.5 mV, which means the signal should read .12 V due to the 35 gain). It then jumps randomly up to .44 for one increment and then back down to -0.00.

    Am I using this amplifier incorrectly? Do you see something wrong with my code? I greatly appreciate any insight. Thank you!