Instruction manual
OCM Pro CF
®
OCM Pro CF - Rev. 09 as of 07.06.2016
page 23
1 Sensor OFR
2 Sensor for level measurement (P-Series or i-series sensors)
3 Combi holder made of stainless steel (ZUB0OFRHAL)
Fig. 6-6
Overview radar, level sensor and holder
6.2 Level measurement using water ultrasound
Depending on the selected sensor type, the water-ultrasonic combi sensor may
contain up to 2 different built-in level measurements: water-ultrasonic and hy-
drostatic level measurement. In this case type POA contains one sensor crystal;
type CS2 uses 2 sensor crystals with different dimensions.
The sensor type CSM does not have an optional level measurement available; it
is a pure flow velocity sensor.
The water-ultrasonic level measurement uses one or more horizontal sensor
crystal(s) utilising the ultrasonic transit time method. Here the period between
transmission and reception of a signal reflected from the water surface is meas-
ured.
2
•
l
t
c
h
l
=
h
= filling level
c
= sound transit time
t
1
= time between transmit and receive signal
The sound travel time in water is 1480 m/s (4.85 fps) at 20 °C (68 °F).
The divergence depending on the temperature is 0.23 % per Kelvin.
To ensure a level measurement which is accurate to the millimetre, the medium
temperature is constantly investigated and the sound transit time is corrected re-
spectively for calculation purposes. The fixed level, which is determined by the
sensor crystal position, is added to the determined value h1. This results in the
total level h.
