Siemens Sitrans 사용자 설명서

Page 14

SITRANS LC 500 – INSTRUCTION MANUAL  

7ML19985GE01

The capacitance of the electrode system is dependent on the dielectric constant of the 
product surrounding the probe. By comparing the capacitances resulting from different 
products with different dielectric constants, it is possible to determine which product is 
surrounding the probe.

Contamination of one product by another can be measured:

100% product A

4 mA

100% product B

20 mA

Values in between 4 and 20 mA represent the ratio of the two products.

The interface between two products can be detected by the change in capacitance from 
one to the other. (See example, 

For Vessels filled with Oil

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. 

The solid-state output can be set to ‘contact open’ or ‘contact closed’ with a covered 
probe.

The adjustable hysteresis and time delay settings allow you to adjust the switch action for 
applications with a lot of surface movement. 

Examples:
With a moving surface that fluctuates between 79% and 80%, if the hysteresis is set 
so that 80 is on and 79 is off, the alarm will constantly alternate between on and off. 
Either set a time delay, or adjust the hysteresis:

• Set the time delay to 10 seconds (for example): the alarm will be on only after 

the surface has been at 80% for at least 10 seconds.

• Reset the hysteresis for 70 (for example): the unit will ignore small surface 

fluctuations between 79 and 80%.