DE2850832A1 - Parity checking circuit for continuous voltage signals - used for process or circuit function monitoring, including multichannel comparator with digital output - Google Patents

Abstract

The circuit has an input channel for each voltage signal and a multi-channel comparator (VG1, VG2) coupled in series with each input channel comparing the respective voltage signal with at least one further voltage signal. Each comparator channel (VG1, VG2) provides a digital output with two possible values, with all the comparator channels (VG1, VG2) connected to a common circuit output (A) via a switch (R), such that an output signal, indicating correct functioning of all circuits etc. is only provided when the output signals form all the channels have a selected value outof the two possible values. Pref. each comparator channel (VG1, VG2) uses different circuit components and/or layout so that they have different responses to temp. variations, store electromagnetic fields etc.

Description

Circuit to compare the synchronization of temporally continuous

nui, erlichen voltage signals The invention relates to a Circuit for comparing the synchronization of time-continuous voltage signals, via a comparator, which has an input for each voltage signal, are linked to a circuit output.

In manufacturing, process and control technology, often two or more, possibly dependent on one another, continuously in time Voltage signals or measured values are checked and monitored for their synchronism. If the signals differ from one another beyond a certain predetermined tolerance range starting, it is ensured by the above circuit that either the entire to monitoring process interrupted or automatically returned to a target value will.

For example, with local transport systems such as gondola lifts, it is necessary to to monitor the operation of the vehicles fully automatically, since the vehicles without a driver operate. For this purpose, e.g. the speed of a vehicle and the The distance between two vehicles driving one behind the other is constantly measured and monitored, that a collision of the vehicles is prevented. Such monitoring must be intrinsically safe, i.e. it must be guaranteed that in the event of a failure or a source of error in the circuits or switching elements used, a collision the vehicles actually cannot enter.

Such problems also occur in other areas of security technology e.g. in the field of process engineering and reactor technology, i.e. in general wherever even under despite failure or damage to individual components In the most unfavorable conditions, a malfunction of the monitored system is reliable must be avoided.

In security technology, intrinsic safety are often multiple namely redundant control systems for processes with security responsibility used that are not single-channel or only with a technical effort that is no longer justifiable can be controlled intrinsically safe. For these reasons, the ones that need to be monitored are often Values are recorded and monitored in at least two channels, in spite of a failure or a defect in one channel can still record correct values via the other channel and to be able to process. This use of multi-channel, not intrinsically safe Systems, responsibility for safety is transferred to the monitoring circuit located on the output side, i.e. a comparator via. This comparator must therefore the Ensure intrinsic safety of the entire system.

In addition to the problem of intrinsic safety, there is often the additional problem that the treated time-continuous voltage signals have a large dynamic range paint over. E.g.

when monitoring the speed of a vehicle on a gondola lift the output of a tachometer generator, for example, between zero and about 15 volts; this Range is monitored from about 100 mV, which in the case of the smallest, corresponds to the speed still to be taken into account. On top of that, as a rule the continuous voltage signals to be monitored within certain relative and absolute tolerance limits or tolerance windows may differ; these tolerance limits are different depending on the type of monitoring and must be through special circuit dimensions can be specified.

The development of single-channel intrinsically safe comparators for temporal continuous voltage signals in the mentioned working range is difficult and often leads to a complicated circuit structure, since in addition to compliance with the The specified tolerance window profiles mentioned also include responsibility for safety for the intrinsic safety of the overall system taken into account in the circuit design must become.

The invention is based on the object of a circuit for comparison the synchronization of temporally continuous voltage signals of the aforementioned Specify the type, whereby the voltage signals are multi-channel, but not intrinsically safe are detected and in which an intrinsically safe comparator or comparator is used which has a simple circuit structure.

This object is achieved according to the invention in that the comparator for the single-channel and non-intrinsically safe detected voltage signals at least is designed with two channels, and that each comparator channel has inputs for all of them comparing voltage signals that each comparator channel has a digital Comparator output for outputting only two distinguishable values Has channel output signal, and that the digital outputs of all comparator channels are linked to the common circuit output via a switch in such a way that that a circuit output signal indicating the functionality of all circuit parts is only generated if all channel output signals have a specific one of the two digital ones Assume values.

According to the invention, the two-channel comparator configuration the comparison of temporally continuous voltage signals to the comparison of temporally discrete ones Tension returned. The output variables of the comparator channels are therefore temporal discrete signals that can only take two distinguishable values, e.g. the Value 1 'logic 1 "and" logic 0 ".

A signal-technically reliable evaluation of the output signals of the comparator channels takes place, for example, by means of a signal-technically safe relay that sends an output signal from the Comparator circuit only allows if the temporally discrete output signals of the Comparator channels the same and at the same time no elements of the entire system are disturbed are.

Since there are usually multiple, non-intrinsically safe control systems in Course of the process control to get the same control information, i.e. for the The case of a gondola lift described above, that for a two-channel detected speed the output value of both channels is the same and therefore different only in the event of a fault Output information is generated, there are no time limits with regard to an upper limit frequency or the swept dynamic range for the comparison of the two temporally discrete signals of the two comparator channels. It can therefore be assumed that the two digital channel output signals can be compared with each other, for example, by means of a relay that is reliable in terms of signaling.

It is also advantageous for the different comparator channels to provide a redundant, in turn, two-channel solution in each case; here it is advantageous, the individual sub-channels from different electronic components or to build up components. In addition, the two comparator channels can also can be realized with different components. By performing with different Components and various electronic solutions can be about circuitry Conditional fluctuations or statistical disturbances in the monitored voltage signals can be practically turned off.

Likewise, drift phenomena of the circuit, as they are with different Environmental conditions can occur that can be controlled by each of the two Comparator channels in the structural design adapted differently to the environment will; For example, a comparator duct can be used as a reinforced thermal insulation insulation get and the other comparator channel a reinforced shield with respect to electromagnetic compatibility (EMC). This means that similar statistical drift phenomena due to the manufacturing process and the circuit design with the same effects in the comparator channels due to the diversity the comparator channels are excluded.

The invention is shown in three exemplary embodiments with reference to the drawing explained in more detail, in the three figures block diagrams each of an embodiment a circuit for comparing the synchronism of two continuous ones Voltage signals is shown. In the figures are the same or have the same effect Elements have been given the same reference numerals.

In Fig. 1 there is an intrinsically safe comparator 1 for two continuous ones Signals shown, which are fed to the comparator at two inputs Ei and E2. The comparator 1 has two comparator channels VG1 and VG2, each for are not intrinsically safe. The inputs El and E2 are each with the two inputs both comparator channels VG1 and VG2 connected, so that the applied temporal continuous voltage signals in the comparator channels simultaneously on their Synchronism must be checked. The circuit structure of the comparator channels corresponds known non-intrinsically safe comparators or comparator circuits for two voltage signals. Depending on the requirements, the above-mentioned, for example, can be used in these comparator channels Tolerance windows are taken into account, within which the values applied to the inputs Voltage signals can move without deviating from the synchronization is registered. The comparator channels are constructed in such a way that their output signals AV1 and AV2 are temporally discrete signals for which there is only the value set "logical" 1 "and" logic 0 "according to the result of the comparison of the input signals gives. The outputs of the comparator channels have two equal signal inputs one signal-technically safe relay R connected, whose normally open contact r in one of the comparators decoupled output circuit with output A. To build such relays see W. Schmitz, Signalrelais, Eisenbahningenieur 20, 1969, p. 2.

Are the two output signals AV1 and AV2 of the comparator channels VG1 or VG2 the same and of the same value indicating an error-free comparison, E.g. "logical 1", the relay R is energized and the normally open contact r of the relay closed so that a signal is present at output A. Just give way to one If the channel output signals AV1 or AV2 fall below this value, the relay also drops out R from and the normally open contact r of the relay interrupts the output circuit, so that on Output A no output signal appears. This indicates that in the overall system from the individual measuring channels for the voltage signals at the inputs and the comparator channels VG1 and VG2 a fault that endangers the safety of the system to be monitored is available. This means that the positively driven normally open / normally closed contacts of the relay a safe information at output A regarding the equality of the inputs applied voltage signals.

For the comparison of the channel output signals AV1 and AV2 by means of a signal technology safe relay, several circuit arrangements can be implemented. According to the embodiment in Fig. 2 is from the digital channel output signals AV1 and AV2 only the channel output signal AV1 of the first comparator channel VG1 is signal-wise Safe relay supplied, whose normally open contact is in the output line of the comparator channel VG2 lies. The output of the comparator circuit is in series behind the normally open contact r in the output line of the second comparator channel.

Here the channel output signal causes AV1 of the first comparator channel only the tightening of the signal-technically safe relay R, if the comparison in the first comparator channel VG1 was found to be correct: In this case the normally open contact r of the relay R is closed and allows the output signal to be evaluated AV2 of the second comparator channel VG2 in the signal-technically safe sense at the output A.

The embodiment of FIG. 3 is in terms of structure of the individual comparator channels VG1 and VG2 according to the exemplary embodiments according to FIGS Figures 1 and 2 are the same, only the channel output signals AV1 and AV2 of the two Comparator channels VG1 and VG2 each have their own signal-safe relay R1 or R2 supplied. The make contacts R1 and R2 of the two relays are in Connected in series in a galvanically isolated output circuit with output A. In the output circuit, an output signal is only generated at output A if Both relays R1 and R2 are energized, i.e. if both comparator channels are independent it has been found from each other that the synchronization between the temporally continuous Voltage signals at the inputs is given. The output signal at output A. is galvanically separated from the comparator arrangement.

In the illustrated embodiments, the comparator channels in terms of circuitry, each executed differently, such as those mentioned above to be able to control statistical fluctuations and drift phenomena. How also As mentioned above, it is also possible for the comparator channels VG1 and VG2 to be multi-channel in each case to be implemented redundantly.

With the specified circuit an intrinsically safe system is created, which is composed of simple, non-intrinsically safe components. Through this the circuits can also be set very easily to the required boundary conditions without any security issues for the individual comparator channels must be taken into account The intrinsic safety is only determined by the circuitry Linking the comparators on the input and output side achieved.

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Claims (3)

Circuit for comparing the synchronization of chronologically continuous Voltage signals DEPARTMENT CLAIMS 1. Circuit to compare the synchronization of temporally continuous voltage signals, via a comparator, which for each voltage signal has an input, linked to a circuit output are, in that the comparator (1) for each single-channel and non-intrinsically safe detected voltage signals at least two-channel is designed, and that each comparator channel (VG1, VG2) inputs for all to comparing voltage signals that each comparator channel has a digital Comparator output for outputting only two differentiable values Channel output signal (AV1, AV2), and that the digital outputs of all Comparator channels with the common circuit output (A) via a switch <R) are linked in such a way that the functionality of all circuit parts indicating Circuit output is generated only when all Channel output signals take a certain of the two digital values. 2. A circuit according to claim 1, characterized in that g e k e n n z e i c h -n e t that each comparator channel (VG1, VG2) redundant and at least again two-channel is executed. 3. Circuit according to one of the preceding claims, characterized g e it is not indicated that the individual comparator channels (VG1, VG2) each consist of different circuit elements or circuit components are constructed circuit according to claim 3, characterized in that the comparator channels (VGl, VG2) circuitry to different interference parameters (environmental influences such as temperature, electromagnetic radiation, etc.) are adapted.