gefran 2850T, Use And Installation Manual

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7. EXAMPLES AND APPLICATION NOTES
80703B_MHW_2850T/3850T_02-2019_ENG
7.3. Correction of linear inputs and outputs
7.3.1. Calibration of input
Calibration and conversion of linear input permits
calibration and conversion into plant engineering units of
the value read by an analogue input by setting four values:
•
Ana min (Minimum number of points)
• Ana max (Maximum number of points)
• Eng min (Minimum converted value, corresponding to
the number of points of Ana min)
• Eng max (Maximum converted value, corresponding to
the number of points of Ana max)
The four values are set via the menu “4.14.1.2.
Configuration
of analogue F-MIX inputs” on page 72.
Example
If you wish to calibrate input 0...10 V as a percentage of
0.0%...100.0%. Let us take, for example, the case in which
the minimum input signal actually corresponds to 100
points, and the maximum to 65000.
To obtain an input variable as a percentage from 0.0% to
100.0%:
•
D.P. = 1
The reference points on the real curve (input) are:
•
Ana min = 100
• Ana max = 65000
The corresponding points on the curve, calibrated and
converted (indication), are :
•
Eng min = 0.0
• Eng max = 100.0
Applying the calibration and conversion reported
above, an input value of 32000 points will be
displayed as 49.3%.
7.3.2. Correction of input
Correction of temperature input permits linearisation of the
signal normally read by the card as required. This is why
the parameters describing part of the linearisation scale are
used
•
Ana min (Minimum temperature level, in tenths of a
degree)
• Ana max (Maximum temperature level, in tenths of a
degree)
• Eng min (Minimum converted value, corresponding to
the number of points of Ana min in degrees)
• Eng max (Maximum converted value, corresponding to
the number of points of Ana max in degrees)
The four values are set via the menu “4.14.1.2.
Configuration of analogue F-MIX inputs” on page 72.
Example
We wish to calibrate the input of a probe around 300.0 °C.
By entering the following values:
•
Ana min = 2950
• Ana max = 3060
• Eng min = 296.0 °C
• Eng max = 305.5 °C
the temperatures read by the card will be recalculated on
the basis of a straight line passing through two points (Ana
min;Eng min) (Ana max;Eng max).
7.3.3. Correction of output
Calibration and conversion of linear output permits
calibration and conversion through particular points of the
value into engineering units associated with the analogue
output through the setting of four values:
•
Eng min (Minimum value of the engineering unit)
• Eng max (Maximum value of the engineering unit)
• Ana min (minimum value of the number of points)
• Ana max (maximum value of the number of points)
When the output is set at an engineering value equal to
Eng min, the physical output will reach the Ana min value
set. This criterion is also applied to management of the
Eng min and Eng max pair, and all values within and outside
the Eng limits are converted using the proportion that links
the parameters entered.
The setting is limited to within the preset scale of 0...32767
for current output, ±32767 for voltage output. This
conversion can be applied to analogue output of all kinds
( ±10 V, 0...20 mA, 4...20 mA).
The four values are set via the menu “4.14.1.4.
Configuration of analogue F-MIX outputs” on page 73.
Example
Output selection 0..20mA.
The values in engineering units (indication) are:
•
Eng min = 0.0
• Eng max = 100.0
The corresponding points on the curve, calibrated and
converted (real output values) are:
•
Ana min = 100
• Ana max = 32000
With the correct curve, an output value equal of 49.3%
will produce generation of a current signal around
9.9mA (16000 points).