VEGA VEGACAL 67 For connection to a signal conditioning instrument - Manual (Page 16)

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5 Connecting to power supply
VEGACAL 67 • For connection to a signal conditioning instrument
31761-EN-130917
5 Connecting to power supply
5.1 Preparing the connection
Always keep in mind the following safety instructions:
•
Connect only in the complete absence of line voltage
•
If overvoltage surges are expected, overvoltage arresters should
be installed
Tip:
We recommend using VEGA overvoltage arresters B63-48 and
ÜSB 62-36G.X.
Power supply and current signal are carried on the same two-wire
cable. The voltage supply range can differ depending on the instru-
ment version.
The data for power supply are specified in chapter "Technical data".
Provide a reliable separation between the supply circuit and the
mains circuits according to DIN VDE 0106 part 101. The VEGA power
supply units VEGATRENN 149AEx, VEGASTAB 690, VEGADIS 371
as well as all VEGAMETs meet this requirement.
Keep in mind the following additional factors that influence the operat-
ing voltage:
•
Output voltage of the power supply unit can be lower under nomi-
nal load (with a sensor current of 20.5 mA resp. 22 mA in case of
fault message)
•
Influence of additional instruments in the circuit (see load values in
chapter "Technical data")
The instrument is connected with standard two-wire cable without
screen. If electromagnetic interference is expected which is above the
test values of EN 61326 for industrial areas, screened cable should
be used.
Use cable with round cross-section. A cable outer diameter of
5 … 9 mm (0.2 … 0.35 in) ensures the seal effect of the cable gland.
If you are using cable with a different diameter or cross-section,
exchange the seal or use a suitable cable gland.
If screened cable is necessary, connect the cable screen on both
ends to ground potential. In the sensor, the screen must be connected
directly to the internal ground terminal. The ground terminal on the
outside of the housing must be connected to the potential equalisa-
tion (low impedance).
If potential equalisation currents are expected, the connection on the
processing side must be made via a ceramic capacitor (e. g. 1 nF,
1500 V). The low-frequency potential equalisation currents are thus
suppressed, but the protective effect against high frequency interfer-
ence signals remains.
Note safety instructions
Voltage supply
Connection cable
Cable screening and
grounding