The formula for calculating equivalent current (ma) from known process variable (PV), Lower range value (LRV) and Upper range value (URV).

The formula is:
4-20mA Current to PV Calculation

SPAN = URV – LRV

Where

PV          =  Process Variable
LRV       =  Low Range Value
URV      = Upper Range Value
mA        = milli ampere

Consider left side of formula for Process variable, LRV of transmitter lower range, Span is the difference between LRV & URV of transmitter ranges.

Consider right side of formula for current (ma), LRV of standard current range .i.e is 4ma,

Span is the difference between LRV (4ma) & URV (20ma) of standard current range

.i.e. 20 – 4 = 16, Using this formula we can calculate mA from pv and as well as pv from mA.

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