GB2171205A - Data logging arrangements - Google Patents

Abstract

A data logging arrangement comprises a logger (10) and a holder (12) for the logger. The logger (10) has mounted thereon a first coil (28) on a core (24) and the holder (12) has mounted thereon a second coil (28') on another core (24'). The logger (10) can be removably engaged with the holder (12) by detents (20) such that, when they are engaged, the windings (28, 28') are positioned with respect to one another so as to be coupled by electromagnetic induction to enable data from a source connected to wires 16 to be collected by the logger (10). The arrangement is described with reference to a water flow-meter in which a rotating magnet in co-operation with a reed switch produces pulses which are read-out when the logger (10) is engaged with holder (12). It is also stated that a pressure sensor in combination with an A/D converter can be similarly used to read out pressure measurements. <IMAGE>

Description

SPECIFICATION Data logging arrangements This invention relates to data logging arrangements.

Data logging arrangements for collecting orac- quiring data from a data source are known. Generally, the operation of setting up such an arrangement to log or collect data from a data source requires at least a moderate amount of technical skill. Further, in the event that, when logging is completed, at least part of the logging arrangement is to be decoupled from the source, for example so that it can be transported to and interrogated at a remote location, the decoupling operation also generally requires at least a moderate amount of technical skill. There are, however, data logging operations in which it would be desirable for these operations to be such as to be capable of safely being carried out, at least in part, by personnel of very limited technical skill.

According to the present invention there is provided a data logging arrangement comprising: a data logger having mounted thereto a first circuit element, and a holder for the data logger that has mounted thereto a second circuit element, the logger being capable of removable engagement with the holder in such a manner that, when the logger and holder are engaged, the first and second circuit elements are positioned with respect to one another so as to be coupled without electrical contact between them to complete a circuit enabling data from a dasa source associated with the holder to be collected by the logger.

Since data logging can be commenced simply by mutual engagement of the logger and holder, and can be stopped simply by mutual disengaging the logger and holder, both operations are very simple to carry out and can, if desired, by carried out by personnel of very limited technical skill. Further, since the first and second circuit elements are coupled without electrical contact between them, that is to say the elements are mutually electrical isolated, safety is greatly enhanced in that there is no need for electrical connections to be made or broken by personnel of limited technical skill.

The "contact-less" coupling between the first and second circuit elements obtained when the holder and logger are mutually engaged can be effected in a variety of ways. Preferably, however, the first and second circuit elements are magnetic elements which are coupled together magnetically when the logger and holder are engaged. In a preferred arrangement disclosed hereinbelow, the first and second circuit elements comprise respective portions of a transformer and, to enhance the magnetic coupling between them, spring means is provided to urge them together when the logger and holder are mutually engaged.

Preferably, the logger and holder are provided with clip means enabling them to be engaged simply by a clipping operation. The clip means may, for example, comprise cooperating detent means on the logger and holder.

To assist engagement of the logger and holder in a desired relative orientation, the holder may be such as to define a cavity or space into which at least part of the holder may be fitted. However, the converse arrangement (i.e. the logger defining a cavity into which at least part of the holder can be received) is possible. So also are other guide means to ensure correct relative orientation of the logger and holder when they are mutually engaged.

In the preferred arrangement described hereinbelow, the logger includes a pulse generator arranged to apply a pulse train having a low or narrow duty cycle. In use, the data source affects the pulse shape, via the second and first data elements,a nd the logger is responsive to the pulse shape to detect the state of the data source. The use of a low or narrow duty cycle conserves power. The preferred arrangement also includes means to at least partially de-energise circuitry inthe logger when the logger is not engaged with the holder. This feature also can conserve power.

The invention will now be further described, by way of illustrative and non-limiting example, with reference to the accompanying drawings, in which: Figure 1 is a somewhat schematic side view of a data logging arrangement embodying the invention comprising a data logger and a holder therefor, the holder being shown in section and part of the logger being broken away to enable a full showing of arts of a transformer mounted to the holder and logger, respectively; Figure 2 is a view of the arrangement, to a smaller scale, in the direction of an arrow II in Figure 1; Figure 3 is a schematic circuit diagram of the data logging arrangement of Figure 1 and 2 and of a utility meter connected to act as a data source for the arrangement;; Figures 4A and 4B represent the waveforms of signals applied to data (D) and clock (C) inputs, respectively, of a latch shown in figure 3; and Figures 5A, 5B and 5C represent waveforms of other signals present in the circuit of Figure 3.

The data logging arrangement illustrated in the drawings comprises a data logger 10 and a holder 12 therefor. The holder 12 is fixed in place in the vicinity of a data source 14 (Figure 3), for example a utility meter such as a water meter, and is connected electrically to the data source by wires 16.

The holder 12 is so shaped as to define therein a parallelepipedal cavity or space 18. The data logger 10 is in the form of a box whose shape corresponds approximately to that of the cavity 18 so that it can, as shown, be received therein. When the data logger 10 is to be engaged within the cavity 18 in the holder 12, it is pushed into the cavity 18 and detents 20 on side walls of the logger 10 are pushed past correspondingly positioned detents 22 on side walls of the cavity so as removably to clip the logger 10 in place within the cavity 18 of the holder 12. To assist the clipping action, the part of the holder 12 defining the cavity 18 and/or the casing of the logger 10 may be constructed of a resiliently deformable material, such as a plastics material.

A cyclindrical ferrite pot core 24 is mounted where shown in Figure 1 to the face of the logger 10 which, in use, is disposed at the inner end of the cavity 18 of the holder 12. (Although shown protruding in Figure 1, the core 24 may in fact be substantially flush with the face of the logger 10 at which it is mounted). The pot core 24 includes a central limb 26. A coil 28 is wound around the limb 26 and encapsulated by a potting material 30.

A similar ferrite pot core 24', also having a central limb 26' having a coil 28' encapsulated in potting material 30', is fitted to the holder 12, the wires 16 being connected to the ends of the coil 28'. More specifically, the core 24' is receved within a sprung metal holder 32 which is disposed in a recess 34 in the back of the holder 12 and which is held in place by means of straps 36.

When the logger 10 is positioned n the holder 12, confronting faces of the pot cores 24,24', which are correspondingly shaped (e.g. as shown, flat), abut one another and there is therefore a good degree of magnetic coupling between them. The detents 20,22 are so positioned that, when the logger 10 is clipped in place, the sprung metal holder 32 is deformed slightly so that the pot cores 24,24' are resiliently urged against one another to ensure a good degree of magnetic coupling between them.

When the logger 10 is in place within the holder, the pot cores 24,24' and the coils 26,26' cooperate to define a transformer 38.

Referring now to Figure 3, the data source 14, which for purposes of the following description is assumed, for example, to be a water meter, has fitted therein a disc-like magnet 40 which is arranged to rotate at a rate proportional to the rate of consumption of water. The magnetic polarity of the magnet 40 is represented schematically in Figure 3 by north (N) and south (S) poles. The magnet 40 is positioned adjacent a magnetic reed switch 42. Thus, the reed switch 42 will be closed or opened, depending upon the angular position of the magnet 40. Accordingly, the number of closures (or openings) of the reed switch 42 is proportional to water consumption.

The logger 10 is sealed and accommodates a power source (battery) for powering the circuity shown schematically in Figure 3. Such circuitry includes a pulse generator 44 which produces a train of sampling/clock pulses at a frequency of, for example, 64 Hz. To maximise battery life, the pulses are produced at a low or narrow duty cycle. In the present arrangement, the duty cycle is, for example, approximately equal to 0.03%. More generally, the duty cycle is preferably less than 0.1%.

An output of the pulse generator 44 is connected to a data (D) input of a D-type flip-flop or latch 46, via resistors 48 and 50, and is connected directly to a clock (C) input of the latch 46. The latch 46 may, for example, be a Motorola 4013, with the data (D) input being used, as described below, as an analog threshold detector. A counter 52 is connected to an output (0) of the latch 46. The junction between the resistors 48,50 is connected via the coil 26 to a positive reference potential (+V).

The logger 10 further comprises a mode or position sensor 54 responsive to the logger 10 not being engaged with the holder 12 or a remote support station containing interrogation circuitry (see below) to de-energise at least part of the circuitry of the logger so as further to maximise battery life. The sensor 54 may comprise one or more reed switches arranged so as closed by a magnet 56 in the holder 12 when the logger 10 is engaged with the holder or to be closed by a magnet when the logger is engaged with the support station.

The operation of the data logging arrangement will now be described. It is assumed that the holder 12 has been fitted to the water meter 14 and that it is desired that the consumption of water over a particular period be monitored or logged. To this end, a logger 10 is fitted to the holder 12 as described above. The circuit shown in Figure 3 is then completed and the logger 10 starts to accumulate the number of closures of the reed switch 42 in the counter 52, as will now be described.

Figure 4A shows one of the pulses from the pulse generator 42 as it appears at the data (D) input of the latch 46. As will be appreciated, the transformer 38 and resistor 48 can be considered to form a sort of potential divider which affects the amplitude of the pulse at the D input of the latch 46. Specifically, since the side of the transformer 38 opposite to the coil 28 will be short circuited or open circuited in dependence upon whether the reed switch 42 is closed or open, the shape of the pulse as appearing at the D input of the latch 46 will depend upon whether the reed switch 42 is closed or open. That is to say, the pulse acts as a sampling pulse to sample the state of the reed switch 42. The solid line in Figure 4A shows the shape of the pulse for the case when the reed switch 42 is closed. As will be seen, the amplitude of the pulse decays rapidly.The dotted lines in Figure 4A show the shape of the pulse when the reed switch 42 is opened. In this case, the pulse amplitude decays much less rapidly.

Figure 4B shows a pulse from the pulse generator 44 as applied to the clock (C) input of the latch 46. As will be seen this pulse, which can be considered to be a clock pulse, is slightly advanced in time with respect to the pulse applied to the data (D) input, which is due to the fact that the pulse applied to the data (D) input is slightly delayed by an R-C network constituted by the resistor 50 and capacitance associated with the resistor. As is known to those skilled in the art, a D-type flip-flop or latch will respond to the state of its data (D) input at the time of a positive-going level change at its clock (C) input, which positive-going level change is provided by the trailing edge of the pulse applied to the clock (C) input. The decision level of the data (D) input is represented at 58 in Figure 4A. As will be seen from comparing Figure 4A and 4B, the level of the pulse at the data (D) input will be determined as being of high level (level "1") if the reed switch 42 is open and will be determined as being of low level (level "0") if the reed switch 42 is closed.

Figure 5A shows the train of pulses supplied by the pulse generator 44. Figure 5B shows the status of the reed switch 42, where the high level represents the switch being open and the low level represents the switch being closed. Suppose that, as represented by the first rising edge in figure 5B, the reed switch 42 has just gone from closed to open.

Generally, this will take place between two of the pulses shown in Figure 5A. At the occurrence of the next pulse subsequent to opening of the switch 42, the latch 46 will clock in level "1" whereby the output Qofthe latch 46, which is represented in Figure 5C, will go from a low level to a high level. At each pulse occurring whilst the switch 42 remains closed, the latch 46 will again clock in level "1" and the output Q will therefore not change. However, upon the occurrence of the next clock pulse subsequent to the switch 42 again closing, the latch 46 will clock in level "0" and the output Q of the latch 46 will go low.

Consequently, the output Q of the latch 46, as represented in Figure 5C, follows the state of the reed switch 42, rounded off to the nearest clock pulse at each end. Therefore, the ouput Q of the latch 46, as accumulated in the counter 52, is representative of the consumption of water detected by the meter 14 during the period in which the logger 10 is received within the holder 12.

At the end of a desired monitoring period, the logger 10 is pulled out of the cavity 18 in the holder 12. (To assist this operation, cut-outs (not shown) may be provided in side walls of the part of the holder 12 defining the cavity 18 to enable the holder 10 to be grasped). The logger 10 can then be taken away to a remote interrogation station where the accumulated data, namely a count representative of water consumption during the monitoring period, may be read out by interrogation circuitry which may, for example, include a ferrite pot core and coil like those 24', 26' of the holder 12 and a magnet operative on another reed switch in the sensor 54 such that the sensor energises the circuitry of the logger and causes the pulse generator 44 to operate at a high frequency to enable reading out to be accomplished quickly.

Although, as described above, the accumulated data is preserved in the counter 52, the circuitry shown in figure 3 may be modified by the provision of further circuitry operative periodically to transfer the contents of the counter 52 to a memory to enable a more comprehensive form of logging. Such circuitry, together with the above-mentioned interrogation circuitry for enabling the data to be read out, is not essential to the present invention. Details thereof may, however, be obtained from a perusal of our co-pending UK Patent Application No. 8503867 filed on the same date as the present application.

As will be appreciated, the operation of inserting the logger 10 in the holder 12 and subsequently removing it therefrom are both very simple and can be carried out by personnel (e.g. meter readers) having substantially no technical skill. The fact that coupling between the logger and holder is effected magnetically means that there are no electrical connections to make or break, thereby enhancing safety, and no unreliable and possibly awkward plug and socket connections that have to be made and broken. As indicated above, the logger 10 is selfpowered by means of an internal battery, and th fact that narrow duty cycle pulses are used, and that the circuitry of the logger is wholly or partially deenergised when the logger is not engaged with the holder 12 or the interrogation circuitry, means that the battery will have long life.The logger 10 is self-contained and very robust. It is, for example, capable of being posted, if desired, to a central interrogation station.

As indicated above, in order to conserve power the duty cycle of the pulse generator 44 is made as low as possible. However, if the duty cycle (and therefore the pulse width) is reduced too much, problems may arise due to reflections of the pulses in the wiring 16 connecting the holder 12 to the data source 14. A trade-off is imposed between the duty cycle and the length of the wiring 16 in that, as the pulse width is reduced, so also is the maximum usable wiring length. For the figures quoted above, i.e. 64Hz with a duty cycle of 0.038%, the pulse width is 6 microseconds. This gives satisfactory results where the length of the wiring 16 is 2 m. For longer wiring, it will probably be necessary to employ a larger pulse width.

Although the arrangement has been described above as being suitable for collecting data from a source 14 in the form of a water meter, it will be evident that it can be applied also to collecting data from various other sources. Thus, as is immediately evident, the logger can log data from any other data source 14than a water meter in which the data is represented digitally by closures of a reed switch or other switch. It can likewise accumulate data in analog form, e.g. pressure, if the source is provided with an analog to digital (A/D) converter which will simulate switch closures. The logger could further be designed so as regularly to emit, via the transformer 38, pulses to synchronise or trigger electronic circuitry associated with the data source and/or holder, for instance to cause the above-mentioned A/D converter to sample a reading of pressure or the like.

The above-described arrangement can, of course, be modified in various ways within the scope of the present invention. For instance, although the two pot cores 24,24' of the transormer 38 are, as described above, urged against one another, the arrangement will still function if there is an air gap between them.

Claims (11)

1. A data logging arrangement comprising a data logger having mounted thereto a first circuit element, and a holder for the data logger that has mounted thereto a second circuit element, the logger being capable of removable engagement with the holder in such a mannerthat, when the logger and holder are engaged, the first and second circuit elements are positioned with respect to one another so as to be coupled without electrical contact between them to complete a circuit enabling data from a data source associated with the holder to be collected by the logger.

2. A data logging arrangement according to claim 1, wherein the first and second circuit elements are magnetic elements which are coupled together magnetically when the logger and holder are engaged.

3. A data logging arrangement according to claim 2, wherein the first and second circuit elements comprise respective portions of a transformer.

4. A data logging arrangement according to claim 3, including spring means arranged to urge the first and second circuit elements together when the logger and holder are mutually engaged.

5. A data logging arrangement according to any one of the preceding claims, wherein the logger and holder are provided with clip means enabling them to be engaged simply by a clipping operation.

6. A data logging arrangement according to claim 5, wherein the clip means comprises cooperating detect means on the logger and holder

7. A data logging arrangement according to any one of the preceding claims, wherein the holder defines a cavity or space into which at least part of the holder may be fitted.

8. A data logging arrangement according to any one of the preceding claims, wherein the logger includes a pulse generator arranged to apply a pulse train having a low or narrow duty cycle to the first circuit element, and means responsive to an effect of the data source on the pulse shape, via the second and first data elements, to detect the state of the data source.

9. A data logging arrangement according to any one ofthe preceding claims, including means to at least partially de-energise circuitry in the logger when the logger is not engaged with the holder.

10. A data logging arrangement according to any one of the preceding claims, wherein the logger includes a counter for accumulating received data, a memory, and means operative periodically to transfer the contents of the counter to the memory.

11. A data logging arrangement substantially as herein described with reference to the accompanying drawings.