Selecting linearisation
Two types of linearisation can be selected:
•
Vessel characteristics as linear
•
Vessel characteristics as a horizontal cylinder
Use the lefthand switch to select whether linearisation is to be carried out at the
electronic insert or by the handheld terminal. If the switch is moved to the right, then
linearisation is carried out at the electronic insert. The handheld terminal cannot now
change the setting. If the switch is moved to the left, then linearisation must be carried
out with the handheld terminal and the switch on the right remains inactive.
Select the type of linearisation for local calibration using the righthand switch. When it
is moved to the left, then the level (output current) is proportional to volume, i.e. the
cross-section of the vessel should be constant over its entire length. When it is moved
to the right, then linearisation is set for a horizontal cylinder, and the measured value
supplied corresponds directly to a percent of full volume.
Empty calibration
With the vessel empty (0 %) both pushbuttons on the left (-) and (+) are pressed
simultaneously in order to set the signal current to the 4 mA lower value. The green
LED lights up to acknowledge that the setting has been accepted. Only when the
green LED goes out is the correct current value of 4 mA shown on the ammeter.
Full calibration
With the vessel full (100 %) both pushbuttons on the right (-) and (+) are pressed
simultaneously in order to set the signal current to the 20 mA upper value. The green
LED lights up to acknowledge that the setting has been accepted. Only when the
green LED goes out is the correct value of 20 mA shown on the ammeter.
Alternative procedure:
calibration with the
vessel almost empty
In this case, the level of product in the vessel must be known as accurately as
possible and should not be too high. A level which is too high reduces the accuracy
of the zero point (corresponding to an empty vessel). An ammeter must be connected
to the electronic insert at Terminals 4 - 5.
Assuming that the level is at 15 %, the current value corresponding to a 15% level
must now be determined. The lower current value can be varied by pressing the two
pushbuttons on the left. The following calculation is used:
➀
The lower current value (= empty vessel, 0 %) is 4 mA.
➁
The upper current value (= full vessel, 100 %) is 20 mA.
➂
This gives a measuring range (‘span’) of 16 mA for a change from 0 to 100 % or a
0.16 mA increase in current for every 1 % rise in level.
➃
For a 15 % level, this is 15 % x 0.16 mA/% or 2.4 mA. This must be added to the
4 mA to give the current value required:
2.4 mA + 4 mA = 6.4 mA
➄
The value 6.4 mA (check with the ammeter) is set by pressing the two pushbuttons
on the left. Pressing pushbutton (+) increases the current and pressing pushbutton
(-) decreases the current.
Note!
•
No indication is given on the green LED when using this procedure.
•
If the operating status is unclear due to an incorrect setting, then all settings should
be reset to factory-set values and the basic calibration carried out again.
Note!
Electronic insert FEC 12 (HART)
4 Calibrating
Hauser
9
