KROHNE BM 70 M - Manual (Page 79)

BM 70 M 79
U = 6...30 V; I
Low
< 110 mA; U
Low
< 2 V;
I
High
< 900 µA (@ U=30V) or I
High
= 200 µA (@ U=8V)
Data: Ex-i switching output
Maximum safety values:
U
i
= 30V; I
i
= 250mA; P
i
= 1W; C
i
≤ 5nF; L
i
≈ 0
Type active (current source)
Current range 4-20 mA (error: 2mA or 22mA)
Accuracy/linearity 0.3 % (rel. 20 mA; 20°C, R
B
=100 Ω )
Temperature drift < 200 ppm/K (typical 70 ppm/K)
Load < 250 Ohm
Load influence < 0.1 % (rel. 20 mA; R
B
= 0...250
Power supply influence < 0.1 % (rel. 20 mA; U
B
in Tol. limits)
Used as switching output:
Low status current < 2 mA
High status current = 22 mA (Load < 500
Ω
Data: current output (non-
communicable; in combination
with RS485)
Open loop voltage < 18 V
Baudrate: 1200 to 38400 Baud
Address: 0 to 255
Data: RS485 interface
Protocols: Krohne protocol,Modbus-RTU, HART
®
Data: PROFIBUS-PA 9... 30 V; Base current 10.5 mA; Fault current 6 mA
Maximum safety values:
U
i
= 30V; I
i
= 300mA; P
i
= 4.2W; C
i
≤ 5nF; L
i
≈ 0
Suitable for connection to intrinsically safe Fieldbus systems
acc. PTB’s FISCO model
Data: FF interface as for PROFIBUS-PA
Local display
Current output: error signal 2 mA (Ex-i: 3.6 mA) or 22 mA
Switching output: open or close contact
Signal on alarm
Digital interfaces: error flags
(only with Ex-e current output HART
®
):
temporarily "freezing" of measurement
Digital input
Voltage: 5...28 V DC; Input resistance: > 1 k
Ω
Measuring accuracy
Temperature: +20°C
Pressure: 1013 mbar abs.
Air humidity: 65%
Well reflecting product (e.g. water) with calm surface
Vessel diameter > 5 m
Mounting distance from wall min. 1/5 × tank height Reference conditions
No interference reflections within the beam angle (± 6°)
(dependent on measuring distance a)
Under reference conditions:
a: block dist. ... 1m: ± 3...2 cm
a: 1 m ... 20 m: ± 2 mm
Error of measurement
a: 20 m ... 35 m: ± 0.01 % of distance
Repeatability < 0.5 × Error of measurement
Measured-value resolution 0.1 mm
Hysteresis < 0.05 × Error of measurement
Transient recovery time Dependent on programmed time constant (1 ... 100 s)
Turn-on drift / characteristics First measured value: approx. 1 minute after switching on
full measuring accuracy: after 2 minutes operating time
Long-term drift Within specified error of measurement