mV output pressure sensor

[Ahmet C.]

Hi,

I have a question about mV output pressure sensors. Beforehand I used V output pressure sensors in order to display the pressure graph with labview. Now I have an old mV output pressure sensor and I don't have any manual. But I discovered the excitation and signal connections and found the output voltages when a 10 VDC excitation voltage is applied as below:

Pressure (PSI)	Voltage (mV)
0	-0,08
500	2,36
1000	4,83
1500	7,28
2000	9,73
2500	12,17
3000	14,62

When I use a V output pressure sensor , I did like this. For example, for 50 PSI I found 2,5 V, 100 PSI I found 5 V, for 200 PSI I found 10 V etc. Therefore I used 20 for scaling. This means, in case of 0,1 V deviation I get 2 PSI error.

However with the mV output pressure sensor as above the first problem is it deviates from linearity ( if the measurement is accepted as true) . And with the same scaling logic I have to use 500 PSI / 2,36 mV = 211864 for scaling or lets say 200000. So this is ridiculuous because if I make a 0,1 mV error in the measurement this corresponds to 20 PSI error.

My question is, if I use a mV output pressure sensor , do I always need a signal amplifier, conditioner etc ? Does it show that I can only take rough measurements with a mV transducer ?

Thanks,

Ahmet

[Wayne.C]

Ahmet,

I suspect that you have a pressure transducer that contains just a strain gauge transducer and no signal conditioning/amplification.  Do you know the PSI range for the transducer?  Do you have any kind of model #.

[Ahmet C.]

This is a Schaevitz P703-0003 pressure sensor. There is not this kind of model anymore. The pressure range for the transducer is 0 to 40bar.

Thanks for your concern,

Ahmet

[Wayne.C]

Ahmet,

A pressure transducer of this type is usually used with some type of signal conditioning/amplification.  Usually identical to what would be used with a load cell.  You would also need to accurately measure the excitation voltage because it is used to help convert the returned value to PSI.  As you will see below, the excitation voltage has a direct effect on the voltage output of the transducer.

The output of a pressure transducer of this type is given in (x) mV/V at fullscale.  What that means is that with fullscale psi applied to the sensor, for each volt of excitation, the transducer will produce (x) mV signal.  For example, if it were rated for an output of 2mV/V and excited with 10 Volts, it would produce a signal of 20mV at full scale PSI.

We do not know the exact output for this transducer but it can be discovered by doing a simple test.

This transducer is rated 0-40 bar or 0 - 580 psi if remembered the conversion correctly.  If you apply 580 psi to the transducer and excite it with exactly 10.000V, it will produce an output voltage (mV).  Dividing this number by 10 should produce the mV/V of the transducer.

[Ashok24]

I am too facing the same issue, can please suggest any of the amplifier or the signal conditioner for this