User's Guide

Table Of Contents

Saab TankRadar

Pro Introduction

1-3

Edition 2. Ref. No: 306010E

Measurement Principle

The Saab TankRadar Pro transmitter sends a microwave signal with a con-

tinuously varying frequency towards the liquid surface. When the reflected

signal returns to the antenna, it is mixed with the outgoing signal.

Since the transmitter continuously changes the frequency of the transmit-

ted signal, there will be a difference in frequency between the transmitted

and the reflected signals.

The gauge mixes the two signals, resulting in a low frequency signal which

is proportional to the distance to the liquid surface. This signal can be

measured very accurately allowing fast, reliable and accurate level measure-

ments.

Saab TankRadar Pro uses an optimum microwave frequency, which reduces

sensitivity to vapour, foam and contamination of the antenna, and keeps

the radar beam narrow in order to minimize influence from walls and

disturbing objects.

Saab TankRadar Pro uses Fast Fourier Transformation (FFT), which is a

well established signal processing technique, to obtain a frequency spec-

trum of all echoes in the tank. From this frequency spectrum the surface

level is extracted. In combination with Saab´s echofixer, FFT allows meas-

max

Frequency (GHz)

Time

∆f

∆f ~ ∆t ~ d

∆t

min

Transmitted

Reflected

f0f1