14
Fig . 4 shows the plug assignment of the preamplifier . As you can see, this
plug has five pins, the outer four assigned exactly as the ones in standard
preamplifiers . In addition to the power supply and signal output of channel
1 and 2, there is a fifth pin, which emits the zero signal .
As a rule, only the four outer pins are needed to evaluate the flow meter
signals; pin assignment is therefore the same as in previously described pre-
amplifiers . For this reason you can use a normal 4-wired connection cable
for the connection of the flow meter . But please make sure that the shielding
of the cable is laid on the plug side onto the metal housing of the plug .
The shielding of the connection cable is placed on both sides . The earth
conductor PE is connected via the shielding from the evaluation electronics
to the preamplifier housing and the meter . The cable shielding should al-
ways be laid continuously as far as the flow meter and not interrupted in
cross connectors or branch sockets . Lay the connection cable as directly
as possible from the evaluating device to the flow meter, since interruptions
are always a potential source of error .
The flow meter must be connected electrically with the earth conductor PE .
This is normally secured by the earthed pipe lines .
If there are potential differences between the preamplifier housing
and the earth conductor PE of the evaluating electronics, you have
to lay a correcting earth.
• Plug assignment of preamplifier
Important:
Only use well-shielded cables for the connection cable, with a wire cross section of
≥ 4 or 5 x 0.25 mm
2
. Please make sure that the housing of the round plug is metallic, that it
has a connection for the shielding and that the potential of the earth conductor PE is
connected with the cable shielding and the housing of the preamplifier.
Important:
Please make sure that no extra inductive elements are connected in the power supply of the
flow meter, such as contactors, relays, valves etc.
These components are potential sources of interference (especially if the inductive elements
are not provided with an adequate protective circuit), generate high interference pulses,
when switched and can interfere with the functioning of the flow meter, although this
complies with the electromagnetic compatibility directives.
Working life is dependent on operating conditions and thus the specific properties of the
devices, limited through wear, corrosion, deposits or age. The operator is responsible for
regular control, maintenance and recalibration. Any indication of a malfunction or damage
prohibits any further use. On request, we can supply you with a borrowed device for the
duration of repair or overhauling. We advice to a yearly control and recalibration.
• Maintenance
pin 1
power supply
U = 10 – 28 V DC
pin 4
digital signal
2. channel
pin 3
power supply
GND (-U = 0 V)
pin 2
digital signal
1. channel
Top view of plug
metal housing connected
with the shielding and the
earth conductor PE
pin 5
digital signal
zero signal
Fig. 4: Flange plug installed in the preamplifier housing of the flow meter
b
b
