Device Description HG G-7335xZA | English, Revision 05 | Date: 19.02.2020
18
Chapter 6 – Hardware
6
Hardware
The casing of the interpreter is made of plastic. All wires etc. can be connected via
M12 connectors on the front panel. The input signals (two per antenna) are ampli
-
fied, filtered with an adjustable band filter (frequency input, see Figure 14 on page
49) and rectified synchronously. Afterwards the direct current is smoothened by a
low-pass filter (see block diagram, Figure 12 on page 48)
6.1 Monitoring
The function of the antennas is controlled: the horizontal component of the field
(sum antenna) is usually controlled by the threshold bits in the system status as a
reference.
The vertical component of the field (difference antenna) equals 0 above the middle
of the wire, but a defective difference channel would always cause a deviation of 0.
That is why both channels are controlled by a DC monitoring. In front of the receiving
inductors, 5V are fed into the circuit, which are passed on from amplifier to amplifier
until reaching the interpreter. If this voltage is applied, the status bits DC1-OK re
-
spectively DC2-OK are set.
6.2 Presettings
To run the interpreter under different conditions without having to change the circuit
board, the input signals have been scaled: An input amplitude of 1 V
pp
reaches a full
range of 75 % between sum channel and the difference channel. The Node-ID is
preset to 1. The maximal incoming signal of all data streams having other frequen
-
cies is 5 V
pp
.
As the parameters of the device (reading height, wire current) can be altered, it is no
problem that the antennas are having different dimensions or being adjusted differ
-
ently.
The interpreter is preset to a frequency of 10 kHz. The threshold for the calculation
of the distances referring itself to 1000 units is preset on input voltage S1 respec
-
tively S2. If the sum voltage lies above this value, the corresponding bit is set in the
system status and the corresponding LED CDx lights up. These presettings can be
modified using a serial terminal (for example HyperTerm on a PC) or via the various
SDOs of the CANopen® protocol (s. Table 26 on page 35).
The two channels of the interpreter have the same presettings.
6.3 Processing the Signal
The four voltages of the four channels are checked every 500 µs and are summed
up during a period of 8 ms. Each 10 ms the CANopen® resp. Profibus protocol are
provided with the measured values. The scaled distances are put out in mms. To cal
-
culate those distances the quotients are formed (current compensated).
The 16x oversampling and the use of a 10bit A/D converter lead to a value range of
the sum voltage of 16384, of the difference voltage of ±8192.
