Azbil SLX 110, User Manual

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Maintenance Azbil Corporation
3-8 Model SLX 110/120 - Smart displacement type level transmitter
3-3 : When output shift is large
Even if the process reaches a stable state of operation (expected temperature, pressure
and specific gravity of the liquid, etc.), this instrument may experience a considerable
output shift, and this may be attributed to influences of temperature in the process.
This instrument measures temperature near the torque tube by using a thermocouple
and compensates the torsional spring constant for temperature (see “2-1 : Principles
of operation” on page 2-1). However, depending on the application, there may
be measurement errors between temperatures measured using the actual torque
tube temperature and the thermocouple, which thus may prevent full temperature
compensation. This applies to, for example, an application which allows a process
fluid such as heated steam or upper layer liquid during measurement of the interface
to enter the torque tube housing.
In order to cope with various environments and applications having the potential
for producing such measuring errors of compensation temperatures, “torque tube
temperature coefficients” (parameters to compensate for measuring errors), which are
satiable by means of SFC communication, are provided.
If an appropriate “torque tube temperature coefficient” is set when the first stable
operation is reached, it is possible to conduct the measurement appropriate for the
application without the need for resetting from the next operation onward.
~Note
Check to see if the specific gravity of the actual liquid to be measured
matches the set specific gravity of this instrument. If they do not match,
set a correct value by means of SFC communication.
Adjustment
1. If the output shift is large even if the specific gravity of the actual liquid to be
measured matches the set specific gravity of this instrument, select either one of
the following to adjust the output:
j
Zero adjustment that adjusts to the level (pinpoint adjustment)
k
Change of torque tube temperature coefficient
Since a selection of the adjustment method requires the current set data, use the
SFC to print out the data (or read the necessary data).
2. substitute values of the necessary set data into the following equation and make a
calculation.
............................... (1)
: Amount of output shift (%)
: Current process temperature (°C)
: Process temperature (°C) during zero adjustment
: Sensor zero angle (*)
: Offset angle (*)
: Sensor span angle (*)