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Problem with pressure transducer

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spintinas

New Member
Hello, my problem is related to pressure transducer. I have a pressure transducer Data Instruments (now Honeywell) AB model 25 psi. Datasheet is here: https://stevenengineering.com/tech_support/PDFs/31DTMAIN.pdf . (My transducer in datasheet is first, AB model). Problem is, that when I power this transducer from usb connector, transducer didn't work correctly. When there is no pressure, I get the 2.5V DC voltage in my multimeter, but according to datasheet Zero Output is 0 + 5 mV. Also, when I pressure transducer there is no change, anyway 2.5V from transducer. In my opinion power source is good, because voltage between Excitation+ and Excitation- is 5V. So, maybe anything of you know what problem it can be?
 

Pommie

Well-Known Member
Most Helpful Member
Your link doesn't work. Could it be that you're reading atmospheric pressure? Are you saying that Zero is 14psi? 14psi on a 25psi transducer would be close to 2.5V.

Mike.
 

JimB

Super Moderator
Most Helpful Member
Looking at the datasheet, you should apply the 5v excitation to the red (+) and black (-) wires, and measure the output between the green (signal +) and white (signal -) wires.

You are probably measuring between the black and one of the green or white wires, where I would expect to see half the excitation voltage, ie 2.5v in your case.

JimB
 

KeepItSimpleStupid

Well-Known Member
Most Helpful Member
Pressure is very wierd. What is the actual model of the sensor. e.f, the Reference ( 1 of 3). What are you trying to measure? What do you expect.

Output an input Z in parallel might put ti close to 0.1A on your USB 5V.

It's probably a bridge transducer, so you need to make a differential measurement,

Absolute and guage pressure will surely mess up your day.
 

spintinas

New Member
Pressure is very wierd. What is the actual model of the sensor. e.f, the Reference ( 1 of 3). What are you trying to measure? What do you expect.

Output an input Z in parallel might put ti close to 0.1A on your USB 5V.

It's probably a bridge transducer, so you need to make a differential measurement,

Absolute and guage pressure will surely mess up your day.
Pressure transducer is absolute. I try to measure pressure from pump used for blood pressure monitors, so the applied pressure for transducer is about 0-200mmHg (0-4 psi), my transducer range is 0-25psi. So, I think i might see voltages between, maybe 0-20mV.
Maybe, there are so options to perform more precise measurements with this transducer?
 
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spintinas

New Member
So, now I check again, and I see that voltage between data signals is ~65mV, in datahsheet i saw, that my transducer is absolute pressure. So, when I try to measure pressure from my blood pressure pump, I see voltage 65mV, which equal to 14,7 psi (atmospheric pressure). 25psi - 100mV, 14,7psi ~50mV, i came to conclusion, that transducer works correctly, but now I have a question, how to perform pressure measurement with this transducer? It's there some ways to callibrate them or any onther options? When I apply some pressure on transducer, still I get value of 65mV (atmospheric pressure).
 

ronsimpson

Well-Known Member
Most Helpful Member
It's there some ways to
You probably need two transducers. One to look at the blood pressure and one to look at room pressure. (subtract readings)
I think you can connect the transducers together so the voltage adds or subtracts.
 
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