Pressure transducer

I'm trying to calibrate a pressure transducer, this type: PX2EN1XX200PSCHX. The output is current, from 4-20mA, and the pressure goes from 0-200PSI. The transducer is intended to be used in a oil-cooling system for a transformer.

I have programmed it in arduino according to the datasheet, and then i tried to test it to see if it gave the expected results. I used an air compressor, and after this the sensor got all messed up. I measured the current to 36 mA in normal room pressure. (should be 4 mA, because the transducer measures 0 PSI at atmospheric pressure.) It worked fine before i plugged it in the air compressor, then it showed 4mA in atmospheric pressure. At the most i had 100PSI on the air compressor. 

Why did this happen?  

Simon Iversen

How are you powering the sensor? If you are applying 5V from the arduino instead of the minimum 8v the sensor requires you may get erroneous current readings.

A quick schematic of how you connected the sensor to the arduino would help figure out what went wrong.

I'm using this power supply: http://www.psui.com/cotek/ge-25.htm, and the pressure transducer is connected to the powersupply (V+)

This worked first, and gave out a value of 4mA on the arduino monitor. But after i used the aircompressor it didn't work.

But the reason might be some silly stuff, i'll try to redo it.

edit:The painting is wrong, the capacitor is of course on the other side of the resistor.

I measured the voltage difference between (v-) and (v+) on the powersupply, and it is always around 10-11 volt. But the values of v- and v+ varies all the time, for example
(v+)=0 volt and (v-)=-10. or (v+)=8 and (v-)=-2

Is this normal, why does the values change, what affects it?

Sounds like you might have ground issues. How is the arduino powered?

IMPORTANT - if your power supplies are not floating, be very careful about connecting V- to arduino ground. If you are using two power supplies and are not sure if they are floating, connect V- to the arduino ground using a 10K resistor and check for voltage across the resistor. if the two power supplies are isolated it will be 0V, otherwise consider powering the arduino from a battery or other floating power supply, or power is directly from V+/V- as outlined below.

I would connect the resistor between the V- and the bottom side of the sensor. Next, connect V- to the arduino ground (or just power the arduino from V+/V-). Now you can use an ADC pin on the sensor side of the current sense resistor and determine the current.

I power the arduino from the computer. But i tried the way you said, after testing if the powersupply was floating, then i connected v- to arduino ground.

Then i connected the resistor between the bottom side of the sensor and v-

But i dont think the problem is with the setup, because no matter what the pressure is on the sensor, the voltage is the same, the pressure of 100psi and 10 psi gives the same voltage. So the problem is with the sensor, it is broken.

But why is it, is this sensor not meant to get connected to air compressors? Because before i started messing with the aircompressor, i got the results i expected.

Thanks for all the help so far.

It is possible that the transducer is not designed to handle air pressure but only liquid pressure as the air molecules could possible seep past the internal seals in the transducer. You would have to check with the component manufacturer to determine is you "blew" the transducer up.

It is also possible depending on if you are using an IC input or ADC that either input was electrically damaged somehow, which could also be possible.