EP2169644B1 - Test of reporting lines on a danger reporting assembly - Google Patents

Description

The invention relates to a method for testing the detection lines of a security alarm system at least to unacceptably high resistance by measuring the current on the terminated with an end module detection line and comparing this current with a setpoint.

The invention further relates to a hazard detection system, which is set up for carrying out this test method, namely a system with a control center, to which at least one signal line is connected directly or via couplers.

Alarm systems have long been designed so that the signal lines connected directly or indirectly to the alarm control panel, in the following "control panel", can be monitored for interruption and short circuit. Common practice is the quiescent current monitoring, in which the respective detection line is completed with a resistance of eg 10kΩ. In a test mode, the control panel or coupler measures the quiescent current on the relevant detection line and compares it with a tolerance field in which the measured current must take into account the line resistance, the number of connected detectors and their respective quiescent current and the terminating resistor. An excessively low current is interpreted as an inadmissibly high series resistance, in extreme cases as an interruption, an excessively high current as an unacceptably low parallel resistance, in extreme cases as a short circuit.

From the EP-A-1 777 671 it is known that a line for feeding z. B. from signalers or other low-impedance consumers (actuators) of a security system to monitor so-called creeping interruption and so-called creeping short circuit. For this purpose, the line with a non-linear element, for. B. a thermistor, a diode or a voltage-controlled transistor in series with a resistor and is operated to test with respect to the triggering of the signal generator (or other actuators) reverse polarity and different, impressed currents. The respectively set voltage at the beginning of the line is compared with reference values. As a result, the comparison provides whether the line is in a proper or faulty state.

A similar monitoring method for a line that feeds at least one alarm device of a hazard alarm system is known from DE-A-10 2005 060 123 known. For this purpose, the line with a low-resistance element, for. B. a diode or a diode in series with a Zener diode, which locks in the current flow direction in which the alarm device is activated blocks. Furthermore, a similar nonlinear element is connected in parallel with each alarm device. For testing, the line is operated with reversed polarity and different impressed currents, from which, in conjunction with the respective voltages at the beginning of the line, the line resistance is calculated and compared with a setpoint range.

These two known test methods are not transferable to reporting lines, because neither the polarity reversal of the supply voltage of a reporting line nor their operation is permissible with varying voltages and currents for testing purposes. By DIN EN 54 Part 13, the requirements for the functionality of the cable-based transmission paths of a security alarm system have been significantly increased. In particular, a standard-compliant installation must ensure that each transmission path under normal load conditions to the relevant component (eg actuator or sensor) supplies the voltage necessary for the function of this component. In contrast to the known systems and their test methods, it is therefore necessary to test for an inadmissibly high resistance of the line under load in the case of a system corresponding to the aforementioned standard. A reporting line must therefore be checked for operability with the connected detectors.

US 3,797,008 shows a fire detection system with a reporting line and a plurality of detectors. The signaling line is closed by a reverse-direction diode diode. A measuring resistor is used to measure the current of the signaling line in order to detect the short-circuiting of the signaling lines by one of the detectors in the event of an alarm, to close a relay and to emit an acoustic alarm. In addition, the voltage at the detection line is measured to detect a line break.

The test is done in accordance with the regulations that, to determine a creeping interruption, an adjustable series resistance (potentiometer) in the line of the signaling line is increased until the alarm system detects an interruption of the signal line that the total resistance of the line at which this condition occurs is measured , then reduced by 10% and then determined whether the reporting line is functional again.

The invention has for its object to provide a method and a hazard detection system available, which determine according to these requirements, whether the reporting line is operational.

In a method having the features of the preamble of claim 1, this object is achieved in that the voltage at the end of the detection line is limited by the end module to a value that is greater than the minimum detector operating voltage, and that the quiescent current by means of the end module on a value is set which is greater than the sum of the quiescent currents of the n detectors (n ≥ 1) and less than the alarm current of a single detector at its minimum operating voltage.

The core idea of the invention is therefore to considerably increase the quiescent current of the signal line in comparison to the quiescent current value range, which is monitored according to the prior art, ie the (apparent) total resistance which can be computationally determined as the quotient of voltage and current at the input of the reporting line To reduce the line significantly, but at the same time to ensure that the voltage at the end of the signal line remains sufficiently high that even the last detector at the end of the line remains fully functional. As will be explained with reference to a numerical example, the test specification according to DIN EN 54 Part 13 can thereby be met, unlike the known monitoring method.

Preferably, the voltage at the end of the reporting line is limited to a value which is approximately equal to the voltage at the input of the reporting line less the maximum allowable in the event of an alarm voltage drop to the end of the reporting line.

In a hazard alarm system with the features of the preamble of claim 3, the above object is achieved in that the final module consists of a non-linear circuit that limits the voltage to a value greater than the minimum detector operating voltage in the idle state of the signal line generates a preset current on the reporting line which is greater than the sum of the quiescent currents of all detectors and less than the alarm current of a single detector at its minimum operating voltage.

If the at least one reporting line is connected directly to the control center, this (controlled by its microprocessor) leads to an inadmissibly high resistance test the reporting line through. As a rule, however, one, but usually several reporting lines are not connected directly but via one or more couplers to the control center. In this case, the respective coupler (controlled by its microprocessor and possibly triggered by a command from the control center) carries out the relevant test.

The end module or the non-linear circuit can very easily consist of a resistor in series with a Zener diode.

Preferably, in series with the resistor and the zener diode, there is additionally a semiconductor component which compensates for its temperature coefficient.

This semiconductor component can be a diode, in particular a zener diode of identical design to the zener diode in the forward direction, because identically constructed zener diodes generally have a very similar temperature coefficient, but when operating in the reverse direction and in the forward direction with different signs.

In a preferred embodiment of the hazard detection system z signaling lines (z ≥ 1) are connected to the center via at least one coupler, which supplies at least one reporting line voltage, is connected via a communication bus to the center and includes a microcontroller, the quiescent current and at least one response Detector measures and evaluates an alarm current of each reporting line.

Fig. 1:

eine nach dem Stand der Technik mit einem Widerstand abgeschlossene Meldelinie und

Fig. 2:

eine mit einem Endmodul nach der Erfindung abgeschlossene Meldelinie.

In the following, the invention will be explained in comparison with the prior art with reference to the drawing. It shows:

Fig. 1:

a closed by the prior art with a resistance signaling line and

Fig. 2:

a terminated with an end module according to the invention reporting line.

The two-wire reporting line in FIG. 1 , in the following also briefly "line", comprises a detector M and a terminating resistor R1, which is very often equal to 10kΩ. Within the scope of the invention FIG. 1 as the end of a reporting line with numerous other, parallel to the detector M and not shown detectors or as a reporting line with only a single detector M, which is connected directly to a central office or a coupler, are considered. In addition, a potentiometer RL is looped into the signal line in order to simulate the test conditions prescribed by the DIN EN54 Part 13 mentioned above for a creeping interruption of the signal line.

In the normal operating state, ie without the potentiometer RL, this detector line has a quiescent current of approximately 900 μA plus the quiescent current of the detector M of, for example, an assumed line voltage of 9.4V. 20μA, with n detectors plus n * 20μA.

Such detectors have a working voltage range of eg 4V to over 12V. To avoid false alarms, the detectors switch off automatically when they fall below the lower working voltage limit and re-initialize when the minimum working voltage is exceeded. In the alarm state, they generate a significantly higher alarm current on the signal line compared to the alarm current. For example, the alarm current may be around 3mA at the lowest working voltage, increase with increasing operating voltage, and be circuitry limited to a maximum value of, for example, 8mA from 7V.

U_E =

Spannung am Leitungsende

U_L =

Spannungsabfall über der Leitung

R_L =

Leitungswiderstand plus eingestellter Widerstandswert RL;

$${\mathrm{U}}_{\mathrm{E}}={\mathrm{I}}_{\mathrm{R}}*\mathrm{R}\mathrm{1}=\mathrm{700}\mathrm{\mu A}*\mathrm{10}\mathrm{k\Omega }=\mathrm{7}\mathrm{V};$$

$${\mathrm{U}}_{\mathrm{L}}={\mathrm{U}}_{\mathrm{A}}-{\mathrm{U}}_{\mathrm{E}}=\mathrm{9}\mathrm{V}-\mathrm{7}\mathrm{V}=\mathrm{2}\mathrm{V};$$

$${\mathrm{R}}_{\mathrm{L}}=\frac{U_L}{I_R}=\frac{2\mathrm{V}}{700\mathrm{\mu A}}=2,86\mathrm{k\Omega }$$

$${\mathrm{R}}_{\mathrm{L}}-\mathrm{10}\%=\mathrm{2},\mathrm{58}\mathrm{k\Omega }$$

(Bedingung der Norm);If a measured at the beginning of the signal line, usually in the coupler quiescent current I _R of less than 700μA at U _{A is} equal to about 9V by definition as a sign of an impermissibly high resistance ("wire break") and consequently the resistance of the potentiometer RL is increased until the quiescent current I _R has fallen to 700μA, then:

U _E =

Voltage at the end of the line

U _L =

Voltage drop across the line

R _L =

Line resistance plus set resistance RL;

$${\mathrm{U}}_{\mathrm{e}}={\mathrm{I}}_{\mathrm{R}}*\mathrm{R}\mathrm{1}=\mathrm{700}\mathrm{uA}*\mathrm{10}\mathrm{k\Omega }=\mathrm{7}\mathrm{V};$$

$${\mathrm{U}}_{\mathrm{L}}={\mathrm{U}}_{\mathrm{A}}-{\mathrm{U}}_{\mathrm{e}}=\mathrm{9}\mathrm{V}-\mathrm{7}\mathrm{V}=\mathrm{2}\mathrm{V};$$

$${\mathrm{R}}_{\mathrm{L}}=\frac{U_L}{I_R}=\frac{2\mathrm{V}}{700\mathrm{uA}}=2.86\mathrm{k\Omega }$$

$${\mathrm{R}}_{\mathrm{L}}-\mathrm{10}\%=\mathrm{2}.\mathrm{58}\mathrm{k\Omega }$$

(Condition of the norm);

If, therefore, the line resistance is reduced to 2.58kΩ with the potentiometer RL and the functionality of the signal line is required, and above all in the event of an alarm, ie at a current I _A equal to approximately 4mA (sum of quiescent current plus detector alarm current), one obtains purely mathematically: $${\mathrm{U}}_{\mathrm{L}\left(\mathrm{alarm}\right)}={\mathrm{R}}_{\mathrm{L}}*{\mathrm{I}}_{\mathrm{A}}=\mathrm{2}.\mathrm{58}\mathrm{k\Omega }*\mathrm{4}\mathrm{mA}=\mathrm{10}.\mathrm{32}\mathrm{V};$$

Consequently, even at a current corresponding to the minimum alarm current I _A, more than the input voltage U _E would drop across the total resistance formed by the potentiometer set by the line and in accordance with the test condition of the standard. Then there is no working voltage at the detector M. The detector can therefore generate no alarm current. The test condition that the detection line is able to function again after the total resistance of the line has been reduced by 10% is in the case of FIG. 1 not achievable.

In the case of FIG. 2 on the other hand, the signaling line is terminated with an end module, consisting of the series connection of a resistor R2, a reverse Zener diode D1 and a forward Zener diode D2.

Assuming for R2 the value of 1kΩ, for the zener diode D1, the zener voltage of 6.8V and for the zener diode D2, the forward voltage of 0.6V, so the quiescent current I _{R is} calculated by the end module at a voltage U _E at the end of the line, for example 9,4V as $$\begin{array}{cc}{\mathrm{I}}_{\mathrm{R}}& =\frac{U_e-\left(U_{\mathit{lock}}+U_{\mathit{passage}}\right)}{R\mathit{1}}=\hfill \\ & =\frac{9.4V-\left(6.\mathrm{8th}V+0.6V\right)}{1\mathrm{k\Omega }}=\frac{2\mathrm{V}}{1\mathrm{k\Omega }}=2\mathrm{mA};\hfill \end{array}$$

$${\mathrm{U}}_{\mathrm{L}}={\mathrm{U}}_{\mathrm{A}}-{\mathrm{U}}_{\mathrm{E}}=\mathrm{9},\mathrm{4}\mathrm{V}-\mathrm{8},\mathrm{8}\mathrm{V}=\mathrm{0},\mathrm{6}\mathrm{V}$$

$$R_L=\frac{U_L}{I_R}=\frac{0,6V}{1,4\mathit{mA}}=429\mathrm{\Omega }$$

$${\mathrm{R}}_{\mathrm{L}}-\mathrm{10}\%=\mathrm{387}\mathrm{\Omega }$$

$${\mathrm{U}}_{\mathrm{L}\left(\mathrm{Alarm}\right)}={\mathrm{R}}_{\mathrm{L}}*{\mathrm{I}}_{\mathrm{A}\left(\max \right)}=387\mathrm{\Omega }*8\mathrm{mA}=3,1\mathrm{V}$$

$${\mathrm{U}}_{\mathrm{Melder}\left(\mathrm{Alarm}\right)}={\mathrm{U}}_{\mathrm{E}}-{\mathrm{U}}_{\mathrm{L}\left(\mathrm{Alarm}\right)}=\mathrm{9},\mathrm{4}\mathrm{V}-\mathrm{3},\mathrm{1}\mathrm{V}=\mathrm{6},\mathrm{3}\mathrm{V}$$

Defining an inadmissibly high resistance ("wire break threshold") below a quiescent current of 1.4mA, then results using the same test conditions as in FIG. 1 for the working _voltage U _{detector (alarm)} applied to the (last) detector in the event of an _alarm : $$\begin{array}{cc}{\mathrm{U}}_{\mathrm{e}}& ={\mathrm{I}}_{\mathrm{R}}*\mathrm{R}\mathrm{2}+{\mathrm{U}}_{\mathrm{lock}}+{\mathrm{U}}_{\mathrm{passage}}=\hfill \\ & =\mathrm{1}.\mathrm{4}\mathrm{mA}*\mathrm{1}\mathrm{k\Omega }+\mathrm{6}.\mathrm{8th}\mathrm{V}+\mathrm{0}.\mathrm{6}\mathrm{V}=\mathrm{8th}.\mathrm{8th}\mathrm{V}\hfill \end{array}$$

$${\mathrm{U}}_{\mathrm{L}}={\mathrm{U}}_{\mathrm{A}}-{\mathrm{U}}_{\mathrm{e}}=\mathrm{9}.\mathrm{4}\mathrm{V}-\mathrm{8th}.\mathrm{8th}\mathrm{V}=\mathrm{0}.\mathrm{6}\mathrm{V}$$

$$R_L=\frac{U_L}{I_R}=\frac{0.6V}{1.4\mathit{mA}}=429\mathrm{\Omega }$$

$${\mathrm{R}}_{\mathrm{L}}-\mathrm{10}\%=\mathrm{387}\mathrm{\Omega }$$

$${\mathrm{U}}_{\mathrm{L}\left(\mathrm{alarm}\right)}={\mathrm{R}}_{\mathrm{L}}*{\mathrm{I}}_{\mathrm{A}\left(\mathrm{Max}\right)}=387\mathrm{\Omega }*\mathrm{8th}\mathrm{mA}=3.1\mathrm{V}$$

$${\mathrm{U}}_{\mathrm{detector}\left(\mathrm{alarm}\right)}={\mathrm{U}}_{\mathrm{e}}-{\mathrm{U}}_{\mathrm{L}\left(\mathrm{alarm}\right)}=\mathrm{9}.\mathrm{4}\mathrm{V}-\mathrm{3}.\mathrm{1}\mathrm{V}=\mathrm{6}.\mathrm{3}\mathrm{V}$$

Under normal testing, therefore, the voltage at the detector M remains above the minimum working voltage even with an alarm current of 8mA. The compared to the example of the FIG. 1 high alarm current value of 8mA is therefore important in practice, because frequently two detectors go into alarm state simultaneously or one after the other and thus the functionality of the hazard alarm system must not be impaired. The detector M in FIG. 2 and thus also all other detectors closer to the line start on the same signal line are thus functioning properly if the total resistance of the line is reduced by 10% with the potentiometer RL below the value that the coupler (or the control panel) interprets as creeping wire break and reports.

In this case, the end module receives no current, because the reverse voltage of the zener diode D1 plus the forward voltage of the temperature-compensated antiserial diode D2, i. 6.8V + 0.6V = 7.4V is fallen below.

As can easily be shown by calculation, the same behavior is achieved with other than the values for the current and the resistances shown in the preceding example. This is especially true for a larger number of detectors M, as the following comparison shows: 1 detector RL for wire breakage (= 1.4mA) : 392Ω RL - 10% : 353Ω U _{E (rest)} : 8,85V U _{E (alarm)} : 6.22V I _A : 7,79mA 30 detectors: RL for wire breakage (= 1.4mA) : 796Ω R _L - 10% : 717Ω U _{E (rest)} : 8,3V U _{E (alarm)} : 4.91V I _A : 5.67mA

The said standard further stipulates that both a creeping and a sudden short circuit must be detected. This is done as usual by comparing the reporting line current with predetermined current limits. Hereupon, the end module proposed here has an effect only insofar as the current limit values have to be adapted to the higher quiescent current, which is determined by the end module in comparison with the hitherto usual termination of the signal line according to FIG FIG. 1 , ie generated with a simple resistance.

Claims (8)

1. Method for checking a detector line of a danger warning system in a non-operational state for excessively high resistance, which detector line is supplied with a constant line voltage and has n detectors (n ≥ 1), said method comprising:

   limiting a voltage at an end of the detector line by means of a terminal module to a value that is greater than a minimum operating voltage of a detector,

   setting a closed-circuit current of the detector line by means of the terminal module to a value that is greater than the sum of closed-circuit currents of the n detectors (n ≥ 1) and smaller than an alarm current of an individual detector at the minimum operating voltage thereof,

   wherein, in order to identify excessively high resistance, the following steps are carried out:

   measuring the closed-circuit current of the detector line terminated by the terminal module,

   comparing the measured closed-circuit current with a target value

   and

   generating an error message if the target value is not met.
2. Method according to claim 1, characterised in that the voltage at the end of the detector line is limited to a value that is approximately equal to the voltage at the input of the detector line, minus the maximum permitted voltage drop up to the end of the detector line in the event of an alarm.
3. Danger warning system comprising
   a control centre,
   at least one detector line that is connected to the control centre,
   at least one detector (M), and
   a terminal module for terminating the detector line,
   wherein the control centre is designed to check the detector line for errors owing to excessively high resistance of said detector line and to generate a "fault" signal in the event of an error,
   wherein the terminal module comprises a non-linear circuit (R1, D1, D2) which, in the non-operational state of the detector line, is designed to limit the voltage to a value that is greater than a minimum operating voltage of a detector, and to generate a pre-set current on the detector line that is greater than the sum of closed-circuit currents of all the detectors (M) and smaller than an alarm current of an individual detector (M) at the minimum operating voltage thereof.
4. Danger warning system according to claim 3, characterised in that the circuit is formed by a resistor (R1) in series with a Zener diode (D1).
5. Danger warning system according to claim 4, characterised in that a semiconductor element (D2) is in series with the resistor (R1) and the Zener diode (D1) and compensates for the temperature coefficients thereof.
6. Danger warning system according to either claim 3 or claim 4, characterised in that a diode is in series with the resistor (R1) and the Zener diode (D1) and compensates for the temperature coefficients thereof.
7. Danger warning system according to any of claims 3 to 5, characterised in that a Zener diode (D2) that is constructed identically to the Zener diode (D1) is in series with the resistor (R1) and said Zener diode in the forward direction.
8. Danger warning system according to any of claims 3 to 7, characterised in that z detector lines (z ≥ 1) are connected to the control centre by means of at least one coupler, which supplies at least the detector line voltage, is connected to the control centre by means of a communication bus, and comprises a microcontroller that measures and evaluates the closed-circuit current, and measures and evaluates the alarm current of each detector line when at least one detector responds.

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