KROHNE BM 70 M - Manual (Page 78)

78 BM 70 M
Annex A: Technical data
Application range Distance, level, volume and reflection measurement of liquids,
pastes and slurries in storage tanks of metal, and also on still
wells
Mode of operation and
system structure FMCW Radar in X-Band (8.5-9.9 GHz) with digital signal
Processing and quartz-controlled PLL frequency stabilisation;
Compact instrument, modular construction
Input
Measured quantity Primary quantities: distance, reflection;
Derived quantities: level, volume
Measuring range Min. distance: 0.5 m
Max. measuring range: 35 m (stillwell: 30 m)
Block distance = antenna length + 10...20 cm
For high accuracy: 1 m
Rate of change in level < 1 m/min
Behaviour when measuring
range exceeded Measured value will stick at the block distance
Output
Output variants
• Variant 1 Ex-e current output HART
®
with switching output and digital
input
• Variant 2 Ex-i current output HART
®
(optionally with Ex-i switching
output or PROFIBUS-PA or FF)
• Variant 3 RS 485 (Krohne protocol or ModBus) with current output
• Variant 4 PROFIBUS-PA (Ex-i), also combined with Var.2 or Ex-i
switching output
• Variant 5 Foundation Fieldbus FF (Ex-i), also combined with Var.2 or
Ex-i switching output
Type active (current source)
Current range 4-20 mA (error: 2mA or 22mA)
Accuracy/linearity 0.05 % (rel. 20mA; 20°C, R
B
=100 Ω )
Temperature drift < 100 ppm/K (typical 30 ppm/K)
Load < 500 Ohm
Load influence < 0.02 % (rel. 20mA; R
B
= 0...500 Ω )
Data: Ex-e current output
Power supply influence < 0.02 % (rel. 20mA;U
B
in Tol. limits)
Max. 100 mA / 30 V DC or 30 V AC Data: switching output
Inner resistance < 20 Ω
Type passive (current sink)
Current range 4-20 mA (error 3.6mA or 22mA);
4 mA constant for HART
®
-Multidrop
Accuracy/linearity 0.05 % (rel. 20mA; 20°C, U=10V)
Temperature drift < 100 ppm/K (typical 30 ppm/K)
Supply voltage 8-30 V (at terminals 31/32)
Load < (U
S
- 8V) / 22mA (U
S
= ext.supply)
Supply voltage influence < 0.02 % (rel. 20mA for U = 8...30V)
Power supply influence < 0.02 % (rel. 20mA; U
S
in Tol. limits)
Data: Ex-i- current output
Maximum safety values:
U
i
= 30V; I
i
= 250mA; P
i
= 1W; C
i
≤ 5nF; L
i
≈ 0