Yokogawa JUXTA MXT - Manual (Page 4)

4 IM 77J04X13-01E 2nd Edition Nov 30, 2005-00
6. COMPUTING FUNCTIONS
6.1 MXT-A Free Program
This computing unit is used to meet individual applications by pro-
gramming the available commands using a PC (VJ77 Parameters
Setting Tool) or the JHT200 Handy Terminal. Set the computing pro-
gram in G01 to G59.
6.2 MXT-R Temperature-Pressure Compensation
This computing unit performs temperature-pressure compensation
(for ideal gas) of differential pressure flow meter using the following
expressions.
“With input limit function” or “without input limit function” can be set for
the input signals X1, X2 and X3.
Y= ··· (1) [with square root extraction of
flow input signal]
K2 · X2+A2
K3 · X3+A3
· K1 · X1
Y= ··· (2) [without square root extraction
of flow input signal]
K2 · X2+A2
K3 · X3+A3
· K1 · X1
where Y (Output): Compensated flow output signal (%)
X1 (Input-1): Uncompensated flow input signal (%)
X2 (Input-2): Pressure input signal (%)
X3 (Input-3): Temperature input signal (%)
K1 to K3: Gain (no unit)
A2 and A3: Bias (%)
With input limit function: Low limit 0%, high limit 100%
● Gain setting (K1 to K3): Set the gain (K1 to K3) in the fixed con-
stants (H01 to H03).
K1 to K3=
±
320 corresponds to H01 to H03=
±
32000%.
Setting range:
−
320 to
+
320
Number of significant digits: 4
Minimum unit: 0.00001
● Bias setting (A2, A3): Set the bias (A2, A3) in the fixed constants
(H04, H05).
A2, A3=
±
32000% corresponds to H04, H05=
±
32000%.
Setting range:
−
32000 to
+
32000%
Number of significant digits: 4
Minimum unit: 0.001%
Decide gain and bias so as not to exceed ± 3.4x10 38 % during compu-
tation. Gain, bias and computation results are 4 significant digits.
● Square root extraction of uncompensated flow input signal:
When extracting the square root of an uncompensated flow input
signal (X1), set in the fixed constant (H06). The lowcut point and
hysteresis shown below can be set in the fixed constants (H07,
H08).
Extract : H06=100%
Not extract: H06=0%
e.g. Set H07=1% to set the lowcut point=1%.
Set H08=0.5% to set the hysteresis=0.5%.
Operation when extracting the square root of an uncompen-
sated flow input signal
Input signal (X)
Output signal
(Y)
0
Lowcut point
Hysteresis
Y=X
● Limit of input signal:
The input limit function limits the input signals X1 to X3 between
0% and 100%.
Set the input limit function in the fixed constant (H09).
With input limit function: H09=100%
Without input limit function: H09=0%
The fixed constants (H01 to H09) can be changed using the
Handy Terminal.
● Computation accuracy:
±
0.1%
However, input (X1) vs. output when K1=K2=K3=1, A2=A3=0%,
and inputs (X2, X3) are fixed at 100%.
6.3 MXT-S Addition / Subtraction
This computing unit adds and subtracts three inputs using the follow-
ing expression.
“With input limit function” or “without input limit function” can be set for
the input signals X1, X2 and X3.
Y = K4 {K1(X1+A1) + K2(X2+A2) + K3(X3+A3)} + A4
where Y (Output): Output signal (%)
X1 to X3 (Input-1 to Input-3): Input signal (%)
K1 to K4: Gain (no unit)
A1 to A4: Bias (%)
With input limit function: Low limit 0%, high limit 100%
● Gain setting (K1 to K4): Set the gain (K1 to K4) in the fixed con-
stants (H01 to H04).
K1 to K4=
±
320 corresponds to H01 to H04=
±
32000%.
Setting range:
−
320 to
+
320
Number of significant digits: 4
Minimum unit: 0.00001
● Bias setting (A1 to A4): Set the bias (A1 to A4) in the fixed con-
stants (H05 to H08).
A1 to A4=
±
32000% corresponds to H05 to H08=
±
32000%.
Setting range:
−
32000 to
+
32000%
Number of significant digits: 4
Minimum unit: 0.001%
Decide gain and bias so as not to exceed
±
3.4x10 38 % during compu-
tation. Gain, bias and computation results are 4 significant digits.
● Limit of input signal:
The input limit function limits the input signals X1 to X3 between
0% and 100%.
Set the input limit function in the fixed constant (H09).
With input limit function: H09=100%
Without input limit function: H09=0%
The fixed constants (H01 to H09) can be changed using the
Handy Terminal.
● Computation accuracy:
±
0.1%
However, when K1=0.5, K2=0.25, K3=0.25, K4=1, and
A1=A2=A3=A4=0%.
6.4 MXT-T Multiplication / Division
This computing unit inputs three signals, multiplies and divides the
three input signals using the following expressions.
“With input limit function” or “without input limit function” can be set for
the input signals X1, X2 and X3.
Y=K4 ·
(K1 · X1+A1) · (K2 · X2+A2)
(K3 · X3+A3)
+A4
where Y (Output): Output signal (%)
X1 to X3 (Input-1 to Input -3): Input signal (%)
K1 to K4: Gain (no unit)
A1 to A4: Bias (%)
With input limit function: Low limit 0%, high limit 100%
● Gain setting (K1 to K4): Set the gain (K1 to K4) in the fixed con-
stants (H01 to H04).
K1 to K4=
±
320 corresponds to H01 to H04=
±
32000%.
Setting range:
−
320 to
+
320
Number of significant digits: 4
Minimum unit: 0.00001
● Bias setting (A1 to A4): Set the bias (A1 to A4) in the fixed con-
stants (H05 to H08).
A1 to A4=
±
32000% corresponds to H05 to H08=
±
32000%.
Setting range: − 32000 to + 32000%
Number of significant digits: 4
Minimum unit: 0.001%
Decide gain and bias so as not to exceed
±
3.4x10 38 % during compu-
tation. Gain, bias and computation results are 4 significant digits.
● Limit of input signal:
The input limit function limits the input signals X1 to X3 between
0% and 100%.
Set the input limit function in the fixed constant (H09).
With input limit function: H09=100%
Without input limit function: H09=0%
The fixed constants (H01 to H09) can be changed using the
Handy Terminal.
● Computation accuracy:
±
0.1%
However, input (X1) vs. output when K1=K2=K3=K4=1, and
A1=A2=A3=A4=0%, and inputs (X2, X3) are fixed at 100%.