KROHNE BM 100A Handbook - Manual (Page 9)

Handbook BM 100 A 9
Nozzles extending into tank
Caution:
Do not use nozzles that extend into the tank. This will block the emitted pulse.
Process connection
For the gauge to make accurate measurements:
• the tank process connection must be level.
• ensure a good fit with the gauge process connection
• the tank roof should not deform under the weight of the gauge
Objects (discontinuities) inside the tank that influence the probe EM (electromagnetic) field
Install the process connection far from protruding objects such as:
• heating tubes
• sudden changes in tank cross-section
• tank wall reinforcements and beams,
• weld lines and dip-stick pipes, etc...
Refer to the figure at the top of the following page.
TDR gauges generate electromagnetic fields when a measurement pulse is emitted. This field is
affected by any nearby discontinuities and these will weaken and potentially block the emitted pulse.
A minimum distance is recommended depending on the probe type to be installed. See the table on
the next page for recommended free space dimensions.
Alternatively, the fitter may use a reference chamber or stilling well. However, the chamber walls
must be smooth (i.e. no visible weld lines), straight and vertical to maintain the pulse strength and
gauge accuracy.
For clean applications only :
Coaxial (type D) probes may be used close to or touching objects or walls as the EM field generated
by the probe is contained within the probe’s outer sheath (refer also to the EM field sizes given in
the figures on the next page).