Basics Sdi-12 - Vega VEGAPULS C 23 Operating Instructions Manual

Permissible residual ripple
Ʋ for 12 V< U < 18 V
B
Ʋ for 18 V< U < 35 V
B
Electrical protective measures
Potential separation
Protection rating
Altitude above sea level
Protection class
Pollution degree
Characteristics and performance data
Measuring frequency
Measuring cycle time
Step response time
11)
Beam angle
12)
Emitted HF power (depending on the parameter setting)
Ʋ Average spectral transmission power
density
Ʋ Max. spectral transmission power
density
Ʋ Max. power density at a distance of
1 m

13.2 Basics SDI-12

Bus description
SDI-12 (1200 bits/sec serial digital interface) is an asynchronous serial communication protocol
for intelligent environmental data acquisition sensors. These sensors typically have a low voltage
requirement (12 V DC), are used at remote measuring points and communicate with data loggers or
other measurement data acquisition systems. The protocol takes into account a master/slave con-
figuration where the master (SDI-12 data logger) requests measurement data from the intelligent
sensors (SDI-12 sensors) with a defined address. The electrical connection is made via a three-core
cable for supply and data transmission. The data are transmitted asynchronously as ASCII charac-
ters as 5 V levels similar to RS 232.
Bus architecture and communication process
At least 10 participants can be connected to an SDI-12 bus with a respective cable length of 60 m.
Longer cable lengths are also possible with fewer bus participants. The SDI-12 standard allows a
sleep mode at the sensor with minimal power consumption, which is interrupted by a signal from
the master. To identify the sensor, each command from the master contains the address of the
Time span after a sudden distance change from 1 m to 5 m until the output signal reaches 90 % of the final
11)
value for the first time (IEC 61298-2). Valid with operating voltage U
Outside the specified beam angle, the energy level of the radar signal is 50% (-3 dB) less.
12)
EIRP: Equivalent Isotropic Radiated Power
13)
VEGAPULS C 23 • SDI-12
≤ 0.7 V (16 ... 400 Hz)
eff
≤ 1 V (16 ... 400 Hz)
eff
Electronics potential free up to 500 V AC
IP66/IP68 (3 bar) acc. to IEC 60529, Type 4P acc. to
UL 50
5000 m (16404 ft)
III
4
W-band (80 GHz technology)
≤ 250 ms
≤ 3 s
4°
13)
-3 dBm/MHz EIRP
+34 dBm/50 MHz EIRP
< 3 µW/cm²
≥ 24 V DC.
B
13 Supplement
41