7ML19985GE04
SITRANS LC500 – OPERATING INSTRUCTIONS
Page 35
Int
e
rc
on
nect
ion
Whenever the local situation allows, the zero adjustment and the full scale can be set
using the push-button feature and the appropriate menu selection. In most cases it is
possible to do a one point calibration
1
by using the push-buttons to input the actual level
in %.
The total isolation between the measurement circuit and the current- loop circuit
provides immunity during the use of cathode protected measuring tanks. Connection to
PLC equipment is possible without any difficulty.
•
The Upper Range Value (URV) and Lower Range Value (LRV) should be within
the USL to LSL range, but can be set anywhere within that range.
•
An interruption of the measuring connection will be detected: a loose or
interrupted connection results in up to 0.5 pF capacitance, which is below the
adjusted LSL and thus signals a FAULT condition.
Applications for Solid-state Output
The solid-state output is a polarity independent switch output. The solid-state switch has
two possible functions.
•
it can be activated/deactivated when the product level reaches the upper/
lower threshold settings (set in menus 15 and 16)
•
or it can be activated if a fault or failure is detected
2
(set in menu 18)
See page 102 for an illustration of a typical application using SITRANS LC 500 as a level
indicator, with the solid-state output connected to a relay which activates a pump.
The solid-state switch has its own parameter set: menu items 13 to18, (see
Menu Levels
00 to 0F and 10 to 1F
on page 37, and
Rotary Switch Positions – Quick Reference
chart on
page 41).
In menu 0E and menu 0F, you set the Upper and Lower Range Values (URV and LRV) for
relay operation. Within that range, the solid-state switch has independent settings for
1.
See
Calibration using push-button adjustment
on page 43.
2.
See
Fault Signalling
on page 16 for details of fault conditions.
Measurement value
Fault- mA Value (F)
F = 1
Fault- mA Value (F)
F = 1
mA
F = 0
Current values for signal detection
0
3.6
3.8
4.0
20 22
20.5
Current values used as signals from digital transmitters