Yokogawa 202 Field Mounting Rate Totalizer - Manual (Page 17)

3.2.2 The Cutoff Point
Because many transducers do not always exactly transmit 4mA when they are at
zero rate, it is often necessary to define a rate below which no integration takes
place. This is termed the cutoff point and is programmed as a percentage of the
Span, S.
For example, if S = 2200 kg/min in a square law system, and the cutoff point is
set at 20.0%, the actual cutoff rate Rc can be determined as follows:
The cutoff rate is defined as:
Rc = 2200 A
At 20% cutoff,
Rc = 2200 x 0.2
= 440 kg/min
The value of A which would produce this cutoff is:
A = 0.04 (since = 0.2) 0.04
and the input signal would be:
I = 16mA x 0.04 + 4mA
= 4.64mA
Programming 15