Device Description HG G-71912-A | English, Revision 03 | Date: 28.03.2018
7
Introduction – Chapter 2
2.3 Function
As the antenna passes over the transponder, it energizes the latter with an energy field of
128 kHz. The transponder returns its code at half of this frequency.
The transponder position in relation to the antenna surface is measured by a coil with ori-
entation in direction of travel. The interpreter decodes the transponder code. Each crossing
of the coordinate axis in driving direction generates a positioning pulse with an adjustable
duration.
The serial output signal is a non-voltaic RS 232. Alternatively it is possible to use a CAN bus.
The positioning pulse is not galvanically separated but available as a +24 V (20 mA) opera-
tional voltage switched output. Optional a 15 bit parallel output for the code (24 Volt
switched, non current limiting) can be effected.
Transponders may also be programmed. Therefore the transponder has to be located within
the antenna field at least 30 ms after starting the programming cycle.
2.3.1 Surveillance Of The Output Stage
The output stage is surveilled concerning the following errors:
–
capacity of oscillatory circuit, short circuit, idling, detuning
–
oscillator breakdown 128 kHz, frequency deviation
–
short-circuit transmitting conductor, idling
–
power transistor is defect
By this surveillance with a certain probability the function can be detected. Defective con-
tacts or ripped-off cables between interpreter and antenna are checked constantly. A non-
authorized change in parameters leads to the setting of a bit in the system status (see also
ATTENTION!
Also the crossing of a massive steel plate may possibly trigger the surveillance!
After programming the transponder an error bit is set, as the surveillance circuit reacts to
the altitude modulation (AM) of the output stage, which is created for programming the
transponder. The error bit is deleted by a successful reference transponder test.
2.3.2 Switchable reference transponder in the antenna
It is recommended that in front of each starting and each change of driving direction a ref-
erence transponder test is proceeded via a serial command. That way, the complete func-
tion of the antenna and of the interpreter is checked cyclically. If the test has been success-
ful, a positioning pulse is output.
2.3.3 Software Update (RS232)
Until up to 10 seconds after turning on the device, an update can be started by using a spe-
cial PC program without opening the system monitor. Additionally, there is a submenu for
the software update in the system monitor (see also chapter 6.3 on page 43).
