Emerson 1420 Reference Manual page 79

Reference Manual
00809-0100-4420, Rev BA
August 2007
Example 3
Offset:
Method 2
Choose a maximum integer equal to or less than 65534, then using the linear
equation presented to solve for A (the scale factor) and B (the offset), as
shown in Example 3.
1. Write the integer value of y (the maximum integer) to the appropriate
I/O point
2. Write the integer value of A (the scale factor) to the appropriate I/O
point
3. Write the integer value of B (the offset) to the appropriate I/O point
The mass flow rate needs to remain between 30 and 40 grams per minute
(g/min). Scale the mass flow rate so 0 represents a flow rate of 40.000 g/min,
and 10,001 represents a flow rate greater than 40.000 g/min.
Solve for A:
Solve for B:
• The maximum integer is 10,000. If the mass flow rate exceeds 40.000
g/min, the transmitter returns the integer 10,001.
• The scale factor is 1000. A change of 1 in the value of the integers
represents a change of 0.001 g/min in the mass flow rate.
• The offset is 62,768. If the mass flow rate drops to 30.000 g/min, the
transmitter returns a 0.
1420 Wireless Gateway
( × ) y
Gain x 32768
1 2
[ ( ) ] 0
100 100 32768
22768
( ) ( 32768 )
10000 A 40 B
( ) ( 32768 )
0 A 30 B
( )
10000 A 10
10000
A
10
A 1000
( ) ( 32768 )
10000 1000 40 B
( 32768 )
10000 40000 B
10000 40000 32768 B
B 62768
E-5