KROHNE BM 70 A_P EN - Manual (Page 8)

Installation and operating instructions BM 70 A/P Page: 8 11/00
3 Input
3.1 Measured variable (distance, level, volume, reflection)
The primary measured variable is the distance between a reference point (as standard: tank mounting
flange) and a reflecting surface (e.g. surface of the liquid).
The filling level is determined by allowing arithmetically for the entered tank height.
Volume measurements are possible by entering a conversion table (max. 50 points).
The strength of the reflected signal can be measured for qualitative assessment of the tank product or
its surface.
3.2 Measuring range [0.5-35/40 m (1.64-115/131 ft)]
Minimum tank height 0.5 m (1.64 ft)
Maximum measuring BM 70 A 40 m (131 ft) / optionally 100 m (328 ft)
BM 70 A mit Wave-Stick 20 m (65.62 ft)
BM 70 P 35 m (115 ft)
The useful range will depend on the antenna size, the reflection properties of the tank product, the
installation position, and the presence of interference reflectors (see Sections 6.1 and 7.5).
3.3 Block distance
The block distance is the minimum measured distance between the mounting
flange (reference point) and surface of the tank product.
Recommended minimum values: see following sketches.
Horn antenna without stilling well:
Product surface Storage tanks: 10cm/4"; Process tanks: 20cm/8"
Antenna size* = Type3: 22cm/8.7"; Type4: 34cm/13";
* Hastelloy: +3cm / 1,2 "
Recommended antenna distance:
The length of any antenna extension used must be added on!
Stilling well / Wave-Guide Wave-Stick
Product
Antenna size * = Type1: 11cm/4";
Type2: 15cm/5.5"; Type3: 22cm/8.7"
Recommended antenna distance =
30 cm / 12"
(Wave-Guide: no antenna)
* Hastelloy: 3 cm (0.4")
Wave-Stick SW: 6cm/2.4"
384 mm/15.1"
Product
max.
200 mm
Standard:
8"
Minimum block distance =
Standard:
184 mm
Normal: Rod length - 200 mm (7.87")
3.4 Out-of-range performance
When the level measuring range is exceeded (including flooding) the measured value will stick at the
(adjustable) block distance (see Sect. 8.6.14).
If the measured value drops below the level range, it will stay put at the set lower range limit (distance
= tank height).
Maximum
level
Block
distance