Siemens Sitrans, LC 500 instruction manual Applications for Solid-state Output, Interconnection

Current values used as signals from digital transmitters

Current values for signal detection

Fault- mA Value (F)			Measurement value	Fault- mA Value (F)
	F = 1			F = 0		F = 1
0	3.6	4.0	20		22	mA
	3.8		20.5

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 calibration1 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 detected2 (set in menu 18)

See page 93 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

Interconnection

1.See Calibration using push-button adjustment on page 43.

2.See Fault Signalling on page 15 for details of fault conditions.

7ML19985GE01 SITRANS LC 500 – INSTRUCTION MANUAL Page 33