what is the diff between range and span

posted by:-Aman yadav


Range:-The range is that difference in minimum and maximum operating parameters that the instrument will withstand without damage.

Span:-The span is that part of the above range over which the instrument has been set up to give a 0% to 100% output signal.

For example:-

1) 0 to 150 Psi, the range is 0 to 150 Psi, 0 for the 0%(4mA) and 150 for the 100%(20mA), the span is 150Psi

2) 20 to 200 Psi, the range is 20 to 200 Psi, 20 for the 0%(4mA) and 200 for the 100%(20mA), the span is 180Psi

3) 40 to 350 °F, the range is 40 to 350 °F, 40 for the 0%(4mA) and 350 for the 100%(20mA), the span is 310°F

the span is: Span = URV(100%) - LRV(0%), or in others word, the units valor traveled through complete range from 0% to 100% , where 0% can be a value different of zero and 100% can be a value different of one hundred.

In some instruments manufacturer the span is equal to the 100% (20mA) value in the units used by the transmitter. (°F, pressure, flow)

The range is the unit valor within of the which the process variable expect to stay or be measured,or controlled.

I hope this help