Endress+Hauser prolevel FMC 661, Operating Instructions Manual

Page: 40 / 56

5.1 Level measurement with automatic calibration correction
This level measurement mode employs a Liquiphant or capacitance probe on channel
2 to check the validity of the calibration on channel 1. If a descrepancy is found, e.g.
because of a change in dielectric constant for capacitance probes or in density for
hydrostatic sensors, the level display is corrected.
The level calibration is corrected every time the product passes the external limit switch,
i.e. uncovered
⇒
covered or covered
⇒
uncovered.
•
If the measured level is less than the installation height of the external limit
switch when this is covered, the value at V8H3 or its volume equivalent is
displayed at V0H0 until the next automatic calibration,
•
If the measured level is greater than the installation height of the external limit
switch when this is uncovered, the value at V8H3 or its volume equivalent is
displayed at V0H0 until the next automatic calibration.
Installation hints Install the external limit switch where:
•
it is frequently covered and uncovered (increases frequency of correction)
•
as near as possible to 100% (ensures greatest accuracy)
- we recommend a height between 70
…
90%.
Note!
•
For Deltapilot S, always use a Liquiphant switch. The use of a capacitance limit
switch causes faulty operation.
•
Product properties may not change during a filling operation, since there is no
means of continuous compensation.
•
The external limit switch must operate with all densities (or dielectric constants)
encountered.
•
If overspill must be avoided at all costs, a separate system must be installed.
•
The automatic correction mode is not recommended for use with bulk solids.
Note!
Hauser
PROLEVEL
FMC 671 123.4
1A
1B
2A
2B
3
H V
+
E
_
Hauser
PROLEVEL
FMC 671 123.4
1A
1B
2A
2B
3
H V
+
E
_
Liquiphant
channel 2
capacitance probe
channel 1
channel 1
hydrostatic sensor
BA142_44
Liquiphant
channel 2
σ, ε ρ
∆
h
0%
0%
∆
h
Fig. 5.2:
Level measurement with
automatic calibration correction:
for dielectric constant with
capacitance probes
for density with hydrostatic
sensors
A capacitance probe can be
used instead of the Liquiphant
(applies to Multicap only)
Chapter 5: Level Measurement with Limit Switch Prolevel FMC 661
36 Hauser