Siemens Treadmill LC 500 사용자 설명서

7ML19985GE01

SITRANS LC 500 – INSTRUCTION MANUAL 

Page 11

The measurement is further protected from interference by a buffer, which applies the 
frequency signal from the measurement section to the active shield section. This effectively 
eliminates any electrical potential difference between the shield and the measurement 
section and prevents additional changes in capacitance occurring.

The relative lengths of the measurement section and active shield section can be 
specified to suit a particular application. If the measured range will be short relative to 
the total length of the electrode, specify a short measurement section. This increases the 
achievable resolution of the measurement, since any change in level will be greater 
relative to the length of the measurement section.

Measuring-

Circuit

Measuring-

Circuit

Conventional Capacitance 

Measurement

SITRANS LC 500 

with Active Shield

C1

C2

C3

R  =  (C1 + C2 + C3) + Ca

(C1 + C2 + C3) + Ca + Cm

R   =  Ca

Ca + Cm

Ca

Ca

Cm

Cm

R  = Ratio between initial 

capacitance and total 
capacitance

Ca = Initial capacitance (air)

Cm = Capacitance Increase 

(product)

C1 = 

Capacitance 

connection 

point

C2  = Capacitance connection 

cable

C3 = Capacitance 

Process 

connection (includes active 
part)

 frequency  (f) 

≈

K

capacitance (C)

active shield

active 
measurement 
section

probe seal 
(inactive)

100%

0%

SITRANS 
LC 500

buffer

empty 

tank

full 

tank