WO2001015113A1

WO2001015113A1 - Arrangement for observations

Info

Publication number: WO2001015113A1
Application number: PCT/FI2000/000720
Authority: WO
Inventors: Raimo Sepponen
Original assignee: Increa Oy
Priority date: 1999-08-24
Filing date: 2000-08-24
Publication date: 2001-03-01
Also published as: FI19991801A

Abstract

The invention relates to an arrangement to register signals from sensors, in which one or more sensor (T1, T2...TN) sends via same or different transfer path signals, which may be coded or modulated in desired way and law obeyed by them is characteristic to each sensor and signal receiving equipment (CAU) use information about transmission cycles of sensors (TP1, TP2, TPN) and ways of modulation.

Description

Arrangement for observations

The present invention relates to an arrangement including method and means to observe several separate targets to be observed and to make it possible to devise with advantageous manner burglar and fire alarm systems, systems to register quantities and industrial monitoring and control systems.

Monitoring systems often include numerous sensors, which are monitored simulta- neously. The sensors can be connected to a loop in which case there can be several sensors in one loop. A central monitoring unit detects changes, which take place in status of the loop and transmits information about the changes forward. If it is required to monitor changes of each sensor, it is required that one has as many loops as sensors or signals from sensors must include some identification code. In both cases, the price of the system is relatively high. If sensors are in radio contact to central, monitoring unit, the contact may be disturbed and this assumes an use of relatively high radio frequency power. In this case an use of battery operated sensors is usually impossible.

An arrangement of the invention is capable to solve the problems described above. Objects of the invention are accomplished by what is set forth in more detail in claim 1 and in the subclaims.

The invention is described in following with reference to the attached drawings, wherein:

Figure 1 shows a monitoring arrangement of the present invention Figure 2 shows a schematical presentation of an output signal from sensors of an arrangement of the present invention. Figure 3 shows a situation in which an occasional noise signal appears among signals from sensors. Figure 4 shows an arrangement of the present invention and in which a signal from a sensor consists of subsignals and the information proportional to a quantity has been encoded to a period between the subsignals of the signal Figure 5 illustrates signal types, which may be used in the communication between a sensor and a central unit

Figure 6 shows one example of a sensor which normally is in stand by state and consumes as few current as possible but will be activated by an effect of a change in the environment. Figure 1 shows a diagram of one arrangement of the present invention. CAU (Central Alarm Unit) is a central unit, which may be for example a central unit of fire or burglar alarm but may monitor also a state of a residential building. CAU may monitor also other devices such as , means to monitor windows and doors being open or closed. Some of the connected sensors T1 , T2 and TN of CAU are shown in the figure, be one or more sensors. The sensors are either connected either with cables or have wireless connection to CAU. Wireless connection refers e.g. to infrared, radio or ultrasound connection. The connection may be also inductive or .

Each sensor transmits its signal, which can be encoded and modulated in as such known ways. It is essential that the signal sent by each sensor will be repeated after in advance set time TP, this time can change according to a beforehand agreed law. Figure 2 shows this in schematic. The sensor T1 transmits its signal so that the period between successive signals will be TP1 , which has been set beforehand. Correspondingly, sensor 2 sends it signals so that the period TP2, which has been set beforehand, is between successive signals. Correspondingly, period between successive signals from TN is TPN. In a simple application said periods TP1 , TP2 and TPN are constant. If interference from surroundings is strong or there are many sensors it may be beneficial, that at least some of the periods are chancing according to laws agreed beforehand. It is advantageous that the changes, which are in accordance with the laws, are based on measurement of time, because it is relatively easy to construct clocks with a good enough accuracy using modern electronics. CAU receives the signals of sensors and calculates weighted time average of received signals. In this case from weighted average of signals signal groups will be devised, and signal peaks (maxima) will be formed in those groups whose averaging cycles correspond the time periods of the sensor signals. CAU may monitor either an existence of a maximum or an appearance of a maximum. It should be mentioned that the sensor characteristic signal to be calculated by CAU may be very complicated function of the signals received by CAU

The method is illustrated in figure 3, where from the signals received by CAU one calculates a sum of periods APN1 , APN2, APN3, and APN4 with an averaging cy- cle of a length of APN. It may be observed, that the output signal of the sensor which has as long transmission cycle as APN, will grow due to the accumulation resulting an accumulating signal SS. But the signal generated by an isolated noise N stays constant.

Likewise, if CAU receives several signals, which have transmission cycles not equal to APN or to a multiplicity of APN, their signals will not be accumulated via calculation. Instead, when one calculates the averaged signal with other length of period one will emphasize the signal from another sensor, whose transmission cycle equals the length of this calculation period. One may change the number of averaged signals according to the need. If one expects a fast response and signal to noise ratio is good the number of averaged signals may be small. Theoretically the averaging improves the signal to noise ratio in respect to each sensor proportional to the square root of the number of signal periods.

The signals from sensors may also be modulated in such a manner that the discrimination capability will be improved. At simplest this may include changing of modulation frequency of pulses by sensors or by function.

It should be mentioned that one might connect to CAU also sensors, which do not use the method described above.

One advantageous application of the arrangement of the invention is the monitoring of moisture in buildings, which is also presented as an example in Figure 6. The monitoring sensor may be battery operated and it is activated by an effect of moisture. After activation, it will send e.g. radiosignal, which will be repeated e.g. with a period of one second. CAU monitors its surroundings and calculates time average of one-second base from signal it has received. In this case, the signal from the activated sensor will accumulate within few averaging cycles and form a clear peak in the averaged signal and CAU will give an announcement of a moisture damage. There may be also another moisture sensor in the same building but it has a transmission period of 1 ,3 second. Therefore, this signal will not be accumulated in the time average calculated with a base of 1 second, but if one calculates a time average with a base of 1 ,3 second, a peak can be clearly observed. In this way one may use the same simple device to observe alarms and discriminate the signals transmitted by different sensors. One possible way to calculate time average of signals is following:

S_l(n) =[S,(t_l +nTP) + S,(n- l)]/2_t where S, (n) is the average and n is an increasing total number.

As can be observed from the equation above, accumulation will take place by such signals, which have a period TP, but those signals, which do not have a period of TP, will be averaged out.

The equation above gives rather heavy weighting on the signal, which has been recently received. In a noisy environment, the weight of a single signal may be reduced by selecting a smaller weighting factor for recently received signal than to the signal average calculated from earlier signals. CAU may evaluate the quality of signals and change weighting factor of recent signal larger if signal to noise is good and correspondingly reduce the factor if signal to noise ratio is low. Weighting factors may depend on the time of the day. So e.g. during working hours the weighting factors related to new signals of burglar alarm sensors are small and after working hours the factors get larger, and therefore the response time gets shorter. This may be controlled with the user interface connected to CAU or via security control system. CAU may include a routine, which detects a maximum of a time average with a certain cycle and compares this to the average of signals. To this routine, one may set a certain threshold value or one may calculate case by case an adaptive threshold value, which is used to detect a peak. Furthermore one should notice that CAU may react with active operations either to the detection of signal from sensor (as in the case of before mentioned moisture alarm) or to the disappearance of signal (e.g. monitoring of elderly people in a home for aged, in this case each old person has own transmitter, which transmit characteristic signal, which has e.g. characteristic transmission cycle). One potential application of the invention is the monitoring of pressure in a gas bottle of a diver. In this case, there is a pressure transducer placed in the gas bottle to measure a quantity proportional to the pressure in the bottle. This for example means a direct measurement of the pressure in the bottle. The pressure information is sent via a suitable transmission path using for example via an inductive connection or using ultrasound, to the receiver, which may be integrated in a diving computer used by the diver.

The transmitter that has been connected to the sensor transmits along the path a signal which can be pulse-type and the repetition period of pulses, TD, as shown in picture 4, is characteristic to the sensor/receiver. The pressure information has been encoded to each pulse. This coding can be done so that the repeatedly sent pulse will contain two subpulses with a period TDP between them. TDP contains the pressure information as presented in Figure 4. This arrangement gives a good signal to noise ratio and prevents the interference generated by the signal sources operating nearby.

A possible application also is the transfer of heart rate information of an athlete from the thorax belt, which register the ECG signal to the wrist unit, which displays the heart rate information. According to the invention each thorax belt/wrist unit pair will have it's own preset transmission cycle TD and the heart rate information may be encoded in the transmission pulse in such a way that the pulse consists two subpulses and the heart rate information is encoded in the time period between the subpulses. Generally, with the method of invention one may transfer signals from sensors in many applications with a high signal to noise ratio. Such applications are e.g. temperature in a room, different quantities to be monitored in industrial processes Figure 5 shows as an example an arrangement of the invention, where the sensor unit TN, which is in contact to the central unit CAU, e.g. via radio path. Sensor unit transmits with preset periods TPN1 the information about stand by status of the sensor; this is illustrated by signal STAND BY. TPN! (which does not need to be a constant) can be relatively long, so that the signal does not disturb other communication and/or the energy consumption of TN will be small. This is important if e.g. in cases where TN has a limited energy source such as a battery. If the state of TN changes e.g. the battery voltage drops below preset limit, TN will send the signal "Battery Low", with a repetition cycle TPN2 (which does not need to be a constant) which is shorter than TPN1. In this case CAU reacts fast to the change in the situation and the user who monitors the state of CAU may change the battery. If TN detects a situation to which it reacts by giving an alarm it will send a signal ALARM. ALARM may be coded in such a manner that CAU reacts immediately as it receives the coded signal or if it receives the signal within preset time period as many times as preset beforehand. This example demonstrates the usability of the invention especially in applications where the alarm situation is not propable, but one must react to that immediately. Applications like this are, among others, bur- glar alarm systems, oil and environmental damage alarm systems, car or ship and their different parts monitoring systems, systems for monitoring of contents of containers, gas monitoring systems in mines, safety monitoring systems for offices and health care centers and monitoring systems of different care institutions. Figure 6 shows an example of a sensor of the invention. This sensor is normally in a state in which it consumes as small amount of energy as possible. In this case, the transducer is designed to monitor moisture for example in such spaces of building where moisture should not normally be present. The electrodes of the sensor SENSOR are placed in such a way that as moisture reaches them a small leakage current will flow between electrodes. These currents bias the FET in a conductive state, which further set transistor TR1 in a conductive state. TR1 switches the transmitter TX to send signal according to the invention, which will be registered by the central unit.

The arrangement may be used also to switch on and of different equipments in building. In this case, as a sensor serves a remote control unit and CAU is placed in the neighborhood of the equipment to be controlled e.g. in the mains connector box of a car heating system. The arrangement may be used also to switch on and off equipments in a summer cottage via telenetworks. In this case, a key code is sent via telenetwork. This initiates a transmission of certain sensor signal in the cottage and in the equipment, e.g. in sauna stove placed CAU controls correspondingly the heating of the stove on or off.

The above only describes a few embodiments of the invention. The invention can be subjected to a plurality of modifications within the scope of the inventional concept defined in the appended claims.

Claims

1. A method to register signals of sensors characterized in that one or more sensor (T1 , T2, ... TN) transmits via same or different transfer path signals, which may be coded or modulated in a desired manner and cycle of signal of each sensor and modulation (TP1, TP2,... TPN) and laws obeyed by them are characteristic for each sensor and in signal receiving device (CAU) knowledge of the cycles of sensors (TP1, TP2,... TPN)and of ways of modulation is utilized.

2. A method as set forth in claim 1 ch a ra cte r ized in that one ormore of cycles of signals (TP1, TP2,... TPN) is constant.

3. A method as set forth in any of claims above characterized in that in signal of one or more sensor (T1 , T2, ... TN) one has coded information proportional to a value of a quantity e.g. in such a way that signal includes two or more subsignals, and time difference (TDP) between them is dependent on the said information proportional to the quantity.

4. A method as set forth in any of claims above characterized in that properties of time average calculated from signals, such as relationship between maxim and average level, are used in processing of information of signal.

5. An equipment including one or more central unit (CAU) and one or more sensor (T1, T2, ... TN), which are in connection with central unit (CAU) via same or different transfer path characterized in that said sensors include means to send signals, which may be coded or modulated in desired ways and transmission cycles of said signals (TP1, TP2,... TPN) are following sensor specific laws and each center unit (CAU) includes means to calculate sensor characteristic functions such as time averages by using information about transmission cycles (TP1 , TP2, TPN) of sensors (T1 ,T2... TN).

. An equipment as set forth in claim 5 characterized in that it includes means to code information proportional to value of quantity registered by one or more sensors (T1 , T2...-TN) in signal transmitted by sensor and at least one central unit includes means to receive this information.

7. An equipment as set forth in claim 5or6characterizedin that said quantity registered by one or more sensor is related to monitoring of state of person, test animal, building or equipment for example in monitoring of heart rate, pressure in gas bottle, humidity, temperature, consumption of electricity or of water, or in monitoring of open or closed states of door of a building.

8. An equipment as set forth in any of the claims 5-7 characterized in that the information which has been registered is used in control of desired function such as turning on robotphone, control of heating element of building or car or control of sauna stove, activating some emergency operations, or control of lightning.