- Varec Radar Tank Gauge Model 7532 RTG Installation & Operations Manual

7532 Commissioning

6.5 Mounting calibration with VU 331

6.5.1 Function group "mounting calibr." (03)

Function "tank gauging" (030)

Using this function, you can either enter a dip table or carry out an auto-correction.

Function "auto-correction" (031)

When measuring levels with radar systems, so-called "multipath reflections" can affect

the level signal giving rise to serious measuring errors. "Multipath reflections" also

include radar beams which are received by the radar system, which have not been

reflected directly by the medium surface. They may reach the antenna via the basin wall

and the medium surface. This phenomenon is particularly noticeable with devices

mounted near to walls, as soon as the conical radar beam strikes the basin wall.

The 7500 RTG can automatically discover and correct measuring errors due to this

"multiple path" propagation. This is because it uses two independent sets of information

when evaluating reflection signals:

• Firstly, it evaluates the amplitude of the reflected energy using the so-called envelope

curve system.

• Secondly, it evaluates the phase of the reflected energy.

The decisive factor for a constant output signal is to assign the phase values to the

associated level values. This assignment is ensured using a correspondence table (index

correction table). The 7500 RTG learns this for the specific application after installation

(learning period).

Therefore, after mounting the device, and after completing the basic calibration, a

history reset must be performed (enter "yes" in the "history reset" (009) function in the

"basic setup " (00) function group).

Do not switch off the radar system during filling and emptying operations during the

teach-in phase. Switching off when there are only negligible level changes produces no

error.

Caution!

During the learning period, fast filling/emptying or turbulent surfaces can result in

switching off and on the phase evaluation. Subsequently observed measurement errors

will disappear as soon as tank levels come back to areas measured by 7500 RTG

previously with activated phase evaluation. If the observed measurement errors are

curetted by dip table entries, the 7500 RTG will take care of these corrections and

automatically adjust the index correction table. Do NOT

correct any settings in the basic

calibration or the extended calibration.

Note!

Immediately after installation, the 7500 RTG measures with the specified mm-accuracy.

Until the level range has been completely covered by the medium (setting up the

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