Resolution increase in PLC's by scaling voltages???Help please

pretty new at this PLC stuff so really need some help.

i have a pressure transducer that has a range of 0-5bars, and a siemens 314ifm PLC with integrated analogue inputs(12 bits)

the problem being that i need a high resolution, and the only pressures i am interested in is between 4-5bars, the rest i do not need.

now my pressure transducer gives me a current of 20mA at 5 bars and 4 mA at 0bars,and 16mA at 4 bars. i need only the 4-5bar pressure(16-20mA) to be spread over the 12 bits to get a higher resolution.

is this possible and if yes please tell me how?the range between0-4 bars is of no use to me

can i do this without changing my transducer. maybe by varying the range in the plc

With some tranducers measuring range can be adjusted with computer/prommer. This would be the easiest solution. Check in data-sheet of transducer, maybe it mentions some protocols like IO-link or says it's programmable.

Another solution is to get an AI module with greater resolution.

Best regards

thank you for all your help,

i have looked up some smart transducers which are of reasonable cost($400-$1000) heres a link to one of them: http://www.ueonline.com/bulletins/tx200-b.pdf

just another question

so basically this is what i'm doing, designing a leak detection system(by measuring the pressure drop), so basically ill be charging a test piece to a pressure of 5 Bars and sealing it, and then measure the pressure drop, which i calculate not to be more than a few hundred pascals.

so heres my question, i now have a smart pressure transducer which is capable of measuring btw 0-5 bars, i have programmed it so that it gives me an output of 4mA at 4 bars, and 20mA at 5 bars. now while the piece is charging my transducer will be exposed to the 0-4 bar range, my question being while the transducer is exposed to the 0-4 bar range what will its output be, or will there be no output, will this range inflict any damage on my transducer?

you might ask why the 0-4Bar range isn't important , its because it has nothing to do with the part testing, and data aquisition.

You don't have to worry. You transducer will not give 36mA in case you have 10bars on your sensor - it will be restricted to 4-20mA or close to it.

When you set it for range 4-5bars <-> 4-20mA, if pressure drops bellow 4bars, your card will return an undershoot; if rises over 5bars it will return overshoot. You can use these options in your program to ignore the measuring while values are not in proper range.

Check the manual for your analog card (i.e. for your CPU) - it should contain a chapter called "Representation of the analog values of analog input channels" or something like that. You will also need to check FC105 (SCALE function).

Also, don't forget that you will probably need a special device for programming the transducer - best option is to tell your supplier to deliver already programmed transducer for desired range.

Best regards