Labom CI4 Series Operating Instructions Manual page 25

6.5.4.3 Upper and lower adjustment
The lower adjustment results in an offset of the characteristic curve. It thus affects zero
and span of the measuring range.
The upper adjustment changes the slope of the characteristic curve by correcting the span
of the measuring range.
Execute the lower adjustment prior to the upper adjustment for a correct full adjustment.
measured
pressure
URV
LRV
LRV
Figure 23: Effect of the upper and lower adjustment on the characteristic curve
You can perform the upper and lower adjustment at any reference pressure level. For in-
stance, you can perform the lower adjustment of a -1...4 bar device at -900 mbar rel. The
reference pressure level for the upper offset can also be freely chosen. For an exact ad-
justment, however, it should be as close to the upper range value as possible.
6.5.4.4 Current adjustment
You can use the current adjustment, if the reading at the end of the measurement chain
(re-converted current value) does not correspond to the measured pressure. With this
function you can compensate deviations in the output stage as well as the downstream
measurement chain.
Proceed as follows (example for 4 mA):
− Select function "Current adjustment" –> "4mA"
− Use "OK" to activate constant current mode (4 mA). CAUTION! The output current
value now no longer corresponds with the measured pressure! This is indicated by
the icon "Function check" (see 6.3.3).
− Read the displayed current value at the end of the measurement chain.
− Enter this current value (e.g. 3.996) at the device. The device now corrects the cur-
rent output so that 4 mA are shown at the end of the measurement chain.
When leaving the function, the constant current mode is disabled and the current value
corresponds again to the measured pressure.
BA_078 Rev 1F6 Level transmitter PASCAL Ci4 LEVEL
1) misaligned
characteristic curve
2) characteristic curve
after lower calibration
(offset shift)
3) characteristic curve
after upper calibration
(span correction)
true
URV pressure
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