KROHNE OPTIWAVE 6300 C, Техническое описание

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PRODUCT FEATURES
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OPTIWAVE 6300 C
www.krohne.com 04/2011 - 4000305604 - TD OPTIWAVE 6300 R04 en
1.3 Measuring principle
A radar signal is emitted via an antenna, reflected from the product surface and received after a
time t. The radar principle used is FMCW (Frequency Modulated Continuous Wave).
The FMCW-radar transmits a high frequency signal whose frequency increases linearly during
the measurement phase (called the frequency sweep). The signal is emitted, reflected on the
measuring surface and received with a time delay, t. Delay time, t=2d/c, where d is the distance
to the product surface and c is the speed of light in the gas above the product.
For further signal processing the difference
Δ
f is calculated from the actual transmit frequency
and the receive frequency. The difference is directly proportional to the distance. A large
frequency difference corresponds to a large distance and vice versa. The frequency difference
Δ
f
is transformed via a Fourier transformation (FFT) into a frequency spectrum and then the
distance is calculated from the spectrum. The level results from the difference between tank
height and measuring distance.
Figure 1-1: Measuring principle of FMCW radar
1
Transmitter
2
Mixer
3 Antenna
4
Distance to product surface, where change in frequency is proportional to distance
5
Differential time delay,
Δ
t
6 Differential frequency,
Δ
f
7 Frequency transmitted
8
Frequency received
9 Frequency
10 Time