KROHNE BM 702 EN - Manual (Page 17)

Installation and operating instructions BM 702 (06/04) 17
After selecting "RECORD": if other parameters had previously been changed, the query
"ACCEPT YES" is first made as to whether they are to be stored. In this case, confirm by
pressing
↵. To record, use the ↑ key to select one of the following options:
• MAX. VALUES: (only maximum values are taken into account when the empty-tank
spectrum is recorded; useful e.g. with “difficult“ agitators).
• AVERAGE: (values are averaged; this setting can be used for most applications).
After selecting with the
↑ key, press the ↵ key to select TOTAL or the ↑ key to select
PARTIAL.
• When TOTAL is selected, the empty-tank spectrum is recorded over the entire range
(tank height).
• If the tank has not been fully drained, the empty-tank spectrum can also be
recorded up to a certain distance, in which case the menu item PARTIAL should be
selected. When this has been selected, a query takes place by way of the
↵ key
concerning the distance value up to which the empty-tank spectrum is to be
recorded. The tank area below the current filling level is then excluded from the
empty-tank recording. It is recommended to maintain a safety distance of 20 to 30
cm from the actual product distance.
Subsequently press key
↵ to start recording the empty-tank spectrum. The display starts
with “200“ and counts down to “0“. The sign WAIT... is shown in the display. READY
appears after approx. 1-3 minutes. Then press key
↵ five times to store the recorded
empty-tank spectrum, which is taken into account for measurements.??
Empty-tank spectrum recording via PC-CAT
Connect the BM 702 and press in the display mode of PC-CAT the key combination Ctrl-L.
The type of empty-tank spectrum can be selected by one of the following keys:
1: Max.Values 4: Max. Partial A: Break
2: Average 5: Avg. Partial
Tank bottom tracing mode (FTB)
The BM 702 includes an additional function for measuring reliably low levels in tanks with
flat bottom and poorly reflecting products (low dielectric constant). This tank bottom tracing
system (abbreviated FTB) is activated in the vicinity of the tank bottom (max. 20% level).
Given higher levels, the normal measuring method is used (reflection from the product
surface).
If the measurement jumps to the correct level only after filling above a certain level (approx.
0.3-1.0 m), you can activate the FTB function Fct. 3.5.7 „PARTIAL“. The relative permittivity
ε
r
of the tank product must be set in Fct. 3.5.8. If it is not known, enter the figure of 2.0.
Since the exact position of the tank bottom must be known for this process, it is advisable
when using the FTB to determine the tank height automatically with an empty tank, using
Fct. 3.5.1.
Conversion table/Volume table
A table consisting of a maximum of 50 points can be stored in the BM 702 for non-linear or
linear conversion of the level, e.g. into a volumetric value. This table, however, can only be
programmed with the PC-CAT program (Fct. 3.7.2).