ABB 264B, Operating Instruction

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. . . ADDENDUM FOR DIFFERENTIAL PRESSURE TRANSMITTERS:
SELECTABLE OUTPUT FUNCTIONS
6.0 POLYNOMIAL 2 (Two polinomial functions of 2nd order)
Analog Output transfer function can also be defined as a two polinomial
function. Both polinomials are of 2nd order. So two different polinomial
functions are used:
Out = [
±
A
0
+A
1
(x
1
)
±
A
2
(x
2
)] + [
±
B
0
+B
1
(x
1
)
±
B
2
(x
2
)]
Here the polinomial with A coefficients is used for X from 0 to a K value,
and the second one with B coefficients for X greater than the K value.
Ax and Bx terms of the polinomials have to be calculated according to
the shape of the vessel.
A PC based software tool is available for polinomial coefficients
definition.
7.0 CONSTANT CURRENT (Loop Test)
This output function, activated by a Configuration Tool, can be used to
test the transmitter output, the integrity of the transmission loop and the
calibration of associated equipment like receivers, recorders, etc.
When this function is activated the transmitter acts like a costant current
generator: using the configuration tool the user can specify a fixed
output current of 4 mA, 20 mA or any value between 4 and 20 mA.
0 K 1
Polinomial with
B coefficients
Polinomial with
A coefficients
= X
Fig. 6b
TX
2nd polinomial function
1st polinomial
function