Festo SFAM, Operating Instructions Manual

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SFAM
Festo – SFAM – 1103a English 67
Characteristic curve for the analogue output
Option Factor Unit Analogue output
0 V or 4 mA 10 V or 20 mA
lower limit upper limit
Standard conditions in accordance with DIN 1343 (1.01325 bar, 0 °C)
OFF 1 [l/min] 0 1000 3000 5000 10000 15000
[scfm] 0 35,31 105,9 176,6 353,1 529,7
Standard conditions in accordance with ISO 2533 (1.01325 bar, 15 °C)
1 1,055 [l/min] 0 1055 3165 5275 10550 15825
[scfm] 0 37,25 111,8 186,3 372,5 558,8
Standard conditions in accordance with ISO 6358 (1 bar, 20 °C)
2 1,087 [l/min] 0 1087 3261 5435 10870 16305
[scfm] 0 38,38 115,15 191,91 383,8 575,7
Tab. 15: Characteristic curve for the analogue output
Example calculations for calculating the maximum occurring characteristic curve deviation:
In the display of an SFAM-1000U a measurement value of 600 l/min will be shown for the flow. How
large can the actual, true flow be, which flows through the sensor?
According to the specification the following apply for nominal conditions (6 bar, 23 °C):
– Precision range: ±3%FS
– Precision zero point: ±0.3%FS.
– (In the example: FS = 1000 l/min)
The overall error during nominal conditions is made up of both of these error variables, which in the
following will be considered separately.
a) Range error
A range error of the measurement signal (= error in the slope of the characteristic curve) has a stronger
effect the larger the measurement value is ( Fig. 12: ). A range error can be designated a sensitivity or
slope error.
z
x = measurement variable (flow)
y = measurement value (display)
z = display value error sought
y
x
Fig. 12: Range error