Help with ML1100 0-10v analog in with 0-5v transducer

I have been handed two 0-5v pressure transducers with a 0-15psi range and need to connect them to the MicroLogix 1100 analog inputs (0-10v) for a storage tank level system.

The min pressure I will will see at the transducer will be 0 psi and the max will be 3 psi. I would not have personally chose this transducer and would also have used an analog input card for better resolution but am forced into the current situation.

What I believe I've figured out is that the ML1100 has a 10 bit resolution (0-1023 raw value) and being that it has a 0-10v input, my 0-5v would translate to 0-511 raw value (assuming the transducer is at it's max of 15 psi).

Assuming that I will only ever see 3 psi as my maximum pressure, my raw value would be 511*(3/15)=102 if my calcs are correct. Clearly this is not a very good way to set this up.

Can someone please point me in a better direction. Thanks in Advance.

Just use the SCP instruction. Put 0 and 1024 in the input min/max and put 0 and 30 in the scaled min/max. Your resolution is 30/1024, or .03PSI.

You are right, your max raw input will be 102 for 3 PSI. At 102 counts thats .03 psi/count, or in a tank level application that about 7/8" of water height.

If however you do need more resolution then maybe get a transducer rated for 0-100 inches of water column (3.6psi). These are made specifically for measuring tank level and may be a better fit anyways since the output is scaled to fluid height for water. All you need to do is compensate for any specific gravity differences. With that sensor your resolution will be .1 inches of fluid height. IFM Efector has this kind of pressure sensor, but there are other manufacturers as well.

>my raw value would be 511*(3/15)=102

It's only 1% resolution but that's probably a better measurement than Bubba writing down what he thinks it is without actually going out to stick the tank.

Many pressure transmitters can be re-scaled in the field. Check that possibility.