Pepperl+Fuchs VBG-EN-K20-D - Earth Fault Detector; Noise Detector; Overvoltage Detector

AS-Interface
Advanced Diagnostics for AS-i Masters
Subject to reasonable modifications due to technical advances. Copyright Pepperl+Fuchs, Printed in Germany
Pepperl+Fuchs Group · Tel.: Germany (6 21) 7 76-0 · USA (3 30) 4 25 35 55 · Singapore 7 79 90 91 · Internet http://www.pepperl-fuchs.com
Issue date - 24.4.2007
124
A duplicate address causes a configuration error und will be shown in the diplay of
the master.
9.4.2 Earth fault detector
An Earth Fault exists when the tension
U
GND
(Nominal value of U
GND
=0,5 U
AS-i
.)
is outside of the following range:
10% U
AS-i
≤ U
GND
≤ 90% U
AS-i
This error limits the fail-safe characteristic of the AS-i transmission substantially.
Earth faults are indicated in the master´s display and AS-i Control Tools.
9.4.3 Noise detector
The noise detector detects alternating voltages on AS-i, which are not produced
by AS-i master or AS-i slaves. These interference voltages can cause telegram
disturbances.
A frequent cause are insufficiently shielded frequency inverters or awkwardly shif-
ted cables.
Noises are indicated in the master´s display and the AS-i Control Tools.
9.4.4 Overvoltage detector
Overvoltages are present, if the AS-i line, whose veins lie normally electrically
symmetrically to the plant earth, are strongly electrically raised. A cause can be
e.g. power-on procedures of large consumers. However sometimes overvoltages
don´t generally disturb AS-i communication, but can release incorrect signals of
sensors.
Overvoltages are indicated in the master´s display and the AS-i Control Tools.
Duplicate addresses can be recognized only in the AS-i segment directly at
the master. If both slaves participate in a duplicate address located behind a
repeater, the duplicate address‘ recognition is impossible.
By a double master in version 1 power supply for 2 AS-i ciruits an earth fault in
one of the both circuits causes also an earth fault in the other circuit because
of the existing galvanic connection.
For recognition of earth faults the master must be grounded with the function
earth.