8
• The unit is not suitable for applications where the probe is subjected to
permanent and high mechanical stress (e.g. fast moving viscous media or fast
flowing media).
•
In case of operation with single probe: When used in plastic tanks, deterioration
caused by electromagnetic interference may occur (noise immunity to
EN61000-6-2). Remedy: (→ 7.6.4)
•
In case of operation with coaxial probe: not suitable for soiled or viscous media,
media containing solid particles and media prone to formation of deposit.
Maximum viscosity: 500 mPa · s.
6 Function
6.1 Measuring principle
Fig. 6-1
Fig. 6-2
D
The unit operates on the principle of guided wave radar. It measures the level
using electromagnetic pulses in the nanosecond range.
The pulses are transmitted by the sensor head and guided along the probe (Fig.
6-1). When they hit the medium to be detected they are reflected and guided back
to the sensor (Fig. 6-2). The time between transmitting and receiving the pulse
directly relates to the travelled distance (D) and the current level. The reference for
distance measurement is the lower edge of the process connection.
The figures show the operation with single probe. In case of operation with
a coaxial probe, the guided wave runs only along the inside of the coaxial
pipe.
