Siemens LC 500, Sitrans instruction manual Application SITRANS LC, Operation & Application

Operation & Application

The entire SITRANS LC 500 transmitter is potted in epoxy resin as part of the intrinsic safety protection. The potting also protects the electronics against mechanical vibration and moisture influences.

The transmitter is connected to the electrode by a mini coaxial cable, and grounded to a connection point inside the enclosure. The external ground lug on the enclosure provides a means of connecting the instrument system ground to a grounded tank or stilling well1. (For more detailed information on grounding requirements, please see Grounding Examples, page 28.)

The measuring range of the SITRANS LC 500 is 3300 pF (1.0 pF ≅ 10–12F).

Note: For safety purposes, and to ensure reliable measurement signals, the external ground lug provided on the SITRANS LC 500 enclosure must be firmly connected by an adequate cable to the grounded vessel or stilling well1.

Application: SITRANS LC 500

The SITRANS LC 500 provides an analog and a solid-state output. The analog output can be either a continuous signal proportional to the reading, or in 2-state mode, a mA signal operating according to NAMUR recommendations for fault signalling2.

0% (LRV) and 100% (URV) can be set anywhere within the measurement range.

1.The loop current provides either: a. an analog signal:

•a reading proportional to level (PV) under normal conditions

•an out-of-limits display, ‘ooL’, alternating with PV, in fault conditions (if the process level exceeds the limit settings [USL] or [LSL])

or:

b.in 2-state mode, provides a mA output:

•4 mA or 20 mA output for 0% and 100%, under normal conditions

•a 3.6 or 22 mA output in fault conditions (when 2-state fault signalling [menu 08] is enabled, if the process level exceeds the limit settings [USL or LSL])

2.The solid-state output can be set to ‘contact open’ or ‘contact closed’, relative to a covered probe: it can be wired to an external relay and used to activate an external alarm or a pump via an auxiliary power circuit. It can be activated under normal conditions by the threshold settings, or Fault signalling can be enabled at menu 18.

1.Where the stilling well is welded to the tank.

2.See page 93 for detailed examples.

Page 12 SITRANS LC 500 – INSTRUCTION MANUAL 7ML19985GE01