Problem in NI Scope measurement?

[KRAZE4LV]

I am facing some problem with pressure measurement.

The pressure range is from 0 to 100 bar, 4mA-20mA and NI scope 5105 Digitizer, which has max voltage range -15V, 15V minivoltage range -25,25mA

but generally the PXI 1031 is reading 1-5V I think so I calculated the linear equation as y=25x-25 and put in my VI.

so according to my equation if x=5V I should get 100bar value but i am just gettig 62bar all time. The value of the data is not increasing beyond 62bar.

Is my calculation wrong for the logic?

or

The measurement I am taking is in the graph form so the value will changel.

I am so confused.

Please let me know I a attching the VI and the NI PXI 5105 specs.

[johnsold]

The PXI 1031 is just the chassis and power supply.  It does not read anything.  So I am guessing that the 5105 is doing the measurements.

What is the resistor value you are using to convert the current to voltage?  Have you verified that the resistor is actually close to the nominal value? Is the voltage in the current loop within the common mode range of the measurement device?  Do you have the loop grounded at two different points?  Does the pressure actually exceed 62 bar?  Does the current from the transducer actually go to 20 mA?

Your calculation is correct for a 1-5 V input corresponding to 0-100 bar.

You have several questions which all seem to be related to the same project.  Do you have a good overall plan for the total project? Did someone sit down and create a specification for the hardware and the software? Have the various subsystems been designed in detail before you started developing code and buying hardware?  Do you have a System Architect (Project Manager, or other title) who has a good overall idea of how this thing is supposed to work?

Without that you will likely continue to be frustrated and not too productive.

Lynn