The RTD is calibrated (3-point) from 0-120 C. The operating range of my process is 50-70 C. Will it have any affect on the accuracy or operation of my temperature transmitter if I change the calibrated range from 0-120 to 0-100?
If the transmitter span is not changed, only the remote display changes.
In choosing ranges, it is routine to place the reading mid-scale, more or less. TBe sure to cover alarm points and off normal readings such as start up, etc. Run it past the operational staff, there may be some issues that are not covered in the design documentation of the original system.
If you change the range of the transmitter, the input range of the receiver, the PLC, DCS, indictor, controller, recorder analog input, must be modified to reflect the change, unless the TT is Foundation Fieldbus, not analog 4-20mA. Not changing the receiver range will give a 20% error at the high end, indicating 120 for a real value of 100.
I doubt the accuracy (comparison to a certified standard) would be affected, but an evaluation of accuracy depends the specs for your particular model, which is unknown.
The minimum required span of temp transmitter is usually less than 50 degrees and yours is well above that, so that's not a problem.
First of you got to understand how these temperature works. Main problem of changing with one sensors with others is the non-linerity behavior of sensors that means the output is not linear with temperature change.
you have to apply some mechanism to make it linear.
if your output ma/mv is ok then you will see the same result as before.