Radar level measurement Radar level measurement The user's guide

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4. Radar level measurementPulse echoes in a process vessel are separated in timeamplitudet 1 t 2 t 3 t 4 t 5timetransmit pulseFig 4.12 With a pulse radar, all echoes (real and false) are separated in time. This allowsmultiple echoes caused by reflections from a parabolic tank roof to be easilyseparated and analysedPulse radar operates entirely withinthe time domain and does not need thefast and expensive processors thatenable the FM - CW radar to function.There are no Fast Fourier Transform(FFT) algorithms to calculate. All ofthe pulse radar processing is dedicatedto echo analysis only.Part of the pulse radar transmissionpulse is used as a reference pulse thatprovides automatic temperature compensationwithin the microwave modulecircuits.The echoes derived from a pulseradar are discrete and separated in time.This means that pulse radar is betterequipped to handle multiple echoes andfalse echoes that are common inprocess vessels and solids silos.Pulse radar takes literally millions of‘shots’ every second. The return echoesfrom the product surface are sampledusing the method described above. Thistechnique provides the pulse radar withexcellent averaging which is particularlyimportant in difficult applicationswhere small amounts of energy arebeing received from low dielectric andagitated product surfaces.The averaging of the pulse techniquereduces the noise curve to allow smallerechoes to be detected. If the pulseradar is manufactured with welldesigned circuits containing good qualityelectronic components they candetect echoes over a wide dynamicrange of about 80 dB. This can makethe difference between reliable andunreliable measurement.59
60Fig 4.11 Block diagram of PULSE radar microwave module
Page 1: Radar levelmeasurementThe user's gu
Page 5 and 6: FM-CW, frequency modulated continuo
Page 7 and 8: FM - CW block diagram (Fig 4.2)The
Page 9 and 10: Mixture of frequencies received by
Page 11 and 12: PULSE radar level transmittersPulse
Page 13 and 14: This periodically repeating signalc
Page 15: EME x MmaxIntegralE x M0minFig 4.10
Page 19 and 20: Choice of frequencyProcess radar le
Page 21 and 22: Antenna focusing and false echoesA
Page 23 and 24: FoamThe effect of foam on radar sig
Page 25 and 26: AccuracyThere is no inherent differ
Page 27 and 28: FM-CW radar bandwidthThe bandwidth
Page 29 and 30: FM - CW frequency spectrum - bandwi
Page 31 and 32: PowerMicrowave powerRadar is a subt

Radar level measurement Radar level measurement The user's guide

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