7ML19985GG03
Pointek CLS500 – INSTRUCTION MANUAL
Page 13
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Oper
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Level Detection
The continuous 4-20 or 20-4 mA signal is proportional to the surface level of the product,
with an accuracy of 0.1% of the actual measurement (for example, 1mm/m). Because the
loop current is in two-state mode for fault signalling, the continuous mA signal is not
available in FSH/FSL mode.
Depending on the requirements of the application, Lower Range Value (LRV - 0%) can be
set to 20 mA and Upper Range Value (URV - 100%) set to 4 mA, or the reverse. The
measurement takes place anywhere within that range. The LCD displays the value as mA,
or pF, depending on the setting for the transmitter variable (TV). If you are using HART, you
have the option to define the units (for example, meters).
2-state Switch
The mA output can be used as a 2-state switch set to either 4 or 20 mA. It can be set to go
to 4 mA if the probe is covered and 20 mA if the probe is uncovered, or the reverse.
Fault Signalling
Pointek CLS500 has three signal output options:
• via the loop-current
• via the solid-state switch
• via HART
Via the loop current
When using the mA signal, Pointek CLS500 operates according to NAMUR standards
1
for
fault signalling. The fault/failure signal can be triggered by a failure in the measuring
system, such as:
• a checksum error
• a loss of signal caused by a defect in the module
• a short circuit in the sensor
• a process failure if the level exceeds the limit settings and if the unit is
programmed to detect this
You can set the Upper and Lower Sensor Limits (menus 0B and 0C) outside the Upper and
Lower Range Value settings. In this case, if the process value is outside its nominal range
(the span between LRV and URV), but still not at a fault/failure level, the continuous mA
output will saturate to 3.8 mA or 20.5 mA. If the process value is outside the Upper or
Lower Sensor Limits, this will be registered as a fault/failure.
1.
See
on page 100 for more details.