Note: Descriptions are shown in the official language in which they were submitted.
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The invention relates to a device for the automatic monit-
oring of the state of an independ~ t electric current suFply
source. In position-determining radio networks for use in traf-
fic systems positional data may be sent by a transponder in
radio rontact with an interrogation unit that is installed in a
vehicle. The interrogation unit can be supplied from the veh-
icle power supply, but the power supply for each transponder may
present serious problems, and independ~nt sources, such as prim-
ary batteries or long-life accumulators, possibly charged via
solar cells, may be preferred. In this case it is desirable to
provide a monitoring sensor having a response threshold which
exceeds the minimum voltage required for satisfactory operation
by a value which can be adjusted in a determinate manner, which
sensor produces an alarm signal if the result of the voltage
measurement carried out during an interrogation, this signal
being fed as a monitoring signal, to a telegram register to be
incorporated in the transponder response.
The `functioning reliability in a punctiform system of this
kind in which data is transmitted from a transponder to a read-
out device by modulated micro-wave signals, is dependent not
only upon the charge state of the indepen ~nt current supply
- source, but also upon the reliable functioning of the circuitry
in these micro-wave devicesO For example, in the event of dam-
age to the housing, this reliable functioning can be severely
influenced in an adverse manner by moisture, which can lead to
sudden breakdowns, or slow deterioration, e.g. where metallic
circuit components do not change their effective electrical
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characteristics significantly until serious corrosion occurs.
Consequently, although the operating reliability of the system
may be impaired in a short or a long term, the harmful influence
of any moisture is not normally distinguishable until the trans-
ponder device actually breaks down.
One object of the present invention is to provide an imp-
roved form of the monitoring device described in the introduct-
ion, in which at the atmospheric humidity within the transponder
device is also monitored.
The invention consists in a device for the automatic mon-
~ itoring of.the state of an independ~nt electric current supply
: . source, for a transponder of a position determining network in a
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traffic.system, which transponder is in radio contact with a
mobile interrogation unit, a voltage charge state monitoring
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;, 15 sensor having a response threshold which exceeds the minimum
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.- voltage required for satisfactory.operatiPn by a value whi-ch may
be set in a determinate manner being provided to produce an
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~ alarm slgnal if the result of the voltage measurement during.any
: interrogation indicates a voltage below said threshold,~and fed
~ 20 via an OR-gate to be included in a telegram- register, and an:~ .
; atmospheric humidity monitoring sensor being provided to check
: that the interior of the transponder is maintained at a low at-
mospheric humidity in its normal operating state, there being
arranged close to the micro wave circuitry which is to be mon-
25 itored a humidity probe which responds to indicate the over-
stepping.of a.given limit value of the atmospheric humidity, and
thereupon produce an alarm signal fed Vla said OR-gate to be
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included in said telegram register.
The invention will now be described with reference to the drawings,
in which:
Figure 1 schematically illustrates one exemplary embodiment construct-
ed in accordance with the invention; and
Figure 2 plots the content of a transponder response signal against
a time scale.
Figure 1 only illustrates the monitoring circuit of a transponder.
A power source having terminals +UB and OV can be connected via a switch Su
10 to a first monitoring stage, comprising a transistor TSl of the npn type, a
collector resistor Rl in its collector circuit, and a voltage divider which
consists of resistors R2 and R3 in series with a Zener diode Z with the
junction of the resistors R2 and R3 being connected to the base of the tran-
sistor TSl. From the collector of the transistor TSl a line Ll leads to one
input of an OR-gate ~, whose output is connected to an input of a telegram
register TR. Via this line Ll a source voltage monitoring signal is fed to the
telegram register TR during any interrogation, if necessary. This monitoring
circuit, which serves to monitor the battery voltage, is designed to be such
that when the voltage falls below a specific voltage, (alarm voltage), the
transistor TSl blocks.
In order that the atmospheric moisture may be monitored, the circuit
is supplemented in the following manner. Parallel to the emitter-collector
path of the first transistor TSl there is connected a second transistor TS2
of the pnp type with a collector load R4 and a voltage divider consisting of
resistors
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R5 R~, and a humidity-dependent resistor R7 connected in series,
the junction oE the resistors R5 and R6 being connected to the
base of -the transistor TS2, whose collector ls connected to the
second input of the OR-gate G. The path of the battery voltage
is via the change-over switch Su, when the latter is actuated by
a monitoring pulse I~ to connect the monitoring circuits briefly
(C~1%o) during the response signal telegram. The illustrated
position of the change-over switch applies to the situation in
which both monitoring circuits, i.e. the monitoring circuits for
the battery charge state and the monitoring circuit for the at-
mospheric humidity, are inactive. In this position the monitor-
ing circuits comprising the transistors TSl and TS2 receive no
operating voltage and the two gate inputs are each supplied, via
the line Ll and resistor Rl, and via the line L2 and resistor
R4, with a logic "0" (OV). By means of the the monitoring pulse I~
the switch Su connects the operating voltage for a short length
of time to the monitoring circuits. When the voltage UB has
fallen below a given threshold value, so that, during the course
of the monitoring pulse I~ the Zener diode Z stops being con-
ductive, then a logic "1" (+UB) is applied to the gate input viathe line Ll and the resistor Rl. If the voltage value of +UB
still exceeds the given threshold value, during the course of
the monitoring pulse I~ the Zener diode Z becomes conductive,
and consequently the transistor TSl conducts. The line Ll is
then connected via the transistor TSl to O V, and no alarm is
produced during the monitoring pulse I~.
The resistance value of the humidity-dependent resistor
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R7 is very closely dependent upon the a-tmospheric humidity, if
possible with logarithmic precision, and in such manner that
the resistance value reduces with increasing atmospheric humidity.
A reduc-tion in the resistance oE the resistor R7 causes -the
transistor TS2 to become conductive and emit a signal in the
form of a logic "1" via the line L2 to the OR-gate G. In order
to economise on operating current, the transistor TS2 and the
transistor TSl are only connected to the operating voltage +U~
via the switch Su within the duration of a monitoring pulse I~.
On delivery, or Eollowing servicing work, the air contained in
the interior of the micro-wave device will have the lowest pos-
sible humidity.
The above described monitoring of the atmospheric
humidity is naturally not limited to use in an answer-back device
of a locating system but can be used correspondingly in any other
housings, and may be used by itself, and not merely in combin-
ation with a battery voltage monitoring unit, as has been described
above.
In the telegram register TR the monitoring signal is
inserted into the telegram produced by the transponder as a
response signal. Figure 2 is a schematic graphical illustration
of a diagram composed of several linked blocks, namely the syn-
chronisation signals SynZ, the answer-back device data AGD, the
monitoring signal UZ, and a parity check signal KZ. In response
to any enquiry from an interrogation unit, the latter is supplied
with a telegram of this kind from the transponder. As this
signal will be received by the central control station,
this is kept constantly informed of possible disturbances in
any transponder.
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