Hey guys! I have a project going, I'm trying to use a pressure transducer as something of a pitot tube to measure air speed. I'm using a PXCPC 0-4 inH20 gage pressure transducer. Data sheet can be found
here
The output of said transducer is 31.25 mV at full scale. I'm using +15V excitation. In order to boost the signal for data acquisition, I'm using an LM358 op amp, with 50 ohm and 15kohm resistors to get a 300 gain.
Here's my quandary. I've verified that my amplification circuits work. (The LM358 is a dual amplifier, one on each side data sheet
here) I used a function generator to output a signal to boost, and then observed through the scope that the signal was boosted by the expected gain of 300.
The pressure transducer works. If I hook it straight up to the board (to analog in 0+, analog in 0- to ground), and look at the scope, I can get some response by blowing in it. Very small, but about what I expect. When I try to hook these things together, nothing happens
.
My setup is as follows. The pressure transducer has 4 pins:
-EXC - hooked to ground
+OUT - hooked to non-inverting IN on near side amplifier
+EXC - Sharing +15V with LM358 op amp
-OUT - hooked to non-inverting IN on far side amplifier
Amplifier VCC shares +15 with pressure xducer
Other side hooked to ground
Out 1 hooked to Analog In 0+
Out 2 (far side) hooked to Analog in 0-
I get nothing on the scope, no response to blowing, just about a 15 mV straight line.
I've tried different configurations, like just using +EXC and +OUT, grounding everything esle, etc, moving wires every which way trying to get SOMETHING to happen. Can you help me make this work? Thanks!
Click thumbnails for large images,
Edited for clarity