KROHNE BM 70 A_P EN - Manual (Page 14)

Installation and operating instructions BM 70 A/P Page: 14 11/00
5 Measuring accuracy
5.1 Reference conditions
•
Temperature = +20°C / +68°F
•
Pressure = 1013 mbar abs. / 14.5 psia
•
Air humidity = 65%
•
Highly reflecting product (e.g. water) with calm surface
•
Tank diameter > 5 m / 16.4 ft
•
Mounted at least 1/7 x tank height away from tank edge (BM 70 P: 1/5 x tank height)
•
No interference reflections inside the radiation lobe (± 6...9°; see Section 6.1.1)
5.2 Error of measurement
Since the measuring process primarily determines distance, measuring accuracy can only be
specified as a function of the distance. For that reason, all figures given in this Section 5 refer to the
measured distance.
BM 70 A: With antenna type 3 (139 mm / 5.47") or type 4 (200 mm / 7.87") or stilling well or Wave-
Guide
-12
-10
-8
-6
-4
-2
0
2
4
6
8
10
12
0 5 10 15 20 25 30 35 40 m
Distance to flange
1
block
distance
Accuracy
-4
-3.2
-2.4
-1.6
-0.8
0
0.8
1.6
2.4
3.2
4
inch cm
4.8
-4.8
16 33 49 66 82 98 115 3 131ft
± 0.3 % ± 1 cm (0.4")
BM 70 A Wave-Stick:
-12
-10
-8
-6
-4
-2
0
2
4
6
8
10
12
0 5 10 15 20 25 30 35 40 m 1 0.18
Accuracy
-4
-3.2
-2.4
-1.6
-0.8
0
0.8
1.6
2.4
3.2
4
inch cm
4.8
-4.8
Distance to flange
16 33 49 66 82 98 115 3 131ft 0.6
± 0.3 % ± 1.5 cm (0.6")