KROHNE OPTIFLEX 2200 C_F EN - Manual (Page 115)

TECHNICAL DATA
8
115
OPTIFLEX 2200 C/F
www.krohne.com 07/2013 - 4000668002 - HB OPTIFLEX 2200 R02 en
8.1 Measuring principle
This Guided Radar (TDR) level meter has been developed from a proven technology called Time
Domain Reflectometry (TDR).
The device transmits low-intensity electromagnetic pulses of approximately one nanosecond
width along a rigid or flexible conductor. These pulses move at the speed of light. When the
pulses reach the surface of the product to be measured, the pulses are reflected back to the
signal converter.
The device measures the time from when the pulse is transmitted to when it is received: half of
this time is equivalent to the distance from the reference point of the device to the surface of the
product. The time value is converted into an output current of 4...20 mA.
Dust, foam, vapour, agitated surfaces, boiling surfaces, changes in pressure, changes in
temperature, changes in dielectric constant and changes in density do not have an effect on
device performance.
The illustration that follows shows a snapshot of what a user would see on an oscilloscope, if the
level of one product is measured.
TDR measurement of level
Figure 8-1: TDR measurement of level
1 Transmitted pulses
2 Reflected pulse
3 Pulse amplitude
4 Time of flight
5 Air, ε
r
= 1
6 ε
r
≥ 1.4 in direct mode or ε
r
≥ 1.1 in TBF mode