SYSTEM FOR ELECTROPHYSIOLOGICAL ANALYSIS OF PLANTS

Abstract

The invention relates to a system for electrophysiological analysis of plants, characterized in that it comprises: a plurality of acquisition systems, each acquisition system comprising: —a plurality of pairs of electrodes each comprising a first electrode and a second electrode each intended to be connected to the same plant in order to pick up first and second analog electric potentials, a plurality of operational amplifiers arranged in order to measure the differences in potential between the first and second analog electric potentials acquired by the first and second electrodes of said acquisition system and a plurality of analog-to-digital converters designed to convert the differences in potential into digital signals, —a central data collection system comprising a memory and a source of electrical power, characterized in that each acquisition system is connected to the central system and comprises: a connecting unit designed to transmit the digital signals to the central system, a power unit designed to transmit the electrical power obtained from the electrical energy source to the operational amplifiers and to the analog-to-digital converters, each acquisition system being designed to galvanically isolate the operational amplifiers and the analog-to-digital converters from the power unit and the connecting unit.

Claims

1. A system for electrophysiological analysis of plants, comprising: a. a plurality of acquisition systems, each acquisition system comprising: i. a plurality of pairs of electrodes each comprising a first electrode and a second electrode each intended to be connected to the same plant in order to pick up first and second analog electric potentials; ii. a plurality of operational amplifiers arranged in order to measure the differences in potential between the first and second analog electric potentials acquired by the first and second electrodes of said acquisition system and a plurality of analog-to-digital converters designed to convert the differences in potential into digital signals; b. a central data collection system comprising a memory and a source of electrical power; and in that each acquisition system is connected to the central system and comprises: c. a connecting unit designed to transmit the digital signals to the central system; d. a power unit designed to transmit electrical power obtained from the electrical energy source to the operational amplifiers and to the analog-to-digital converters; and in which each acquisition system is designed to galvanically isolate the operational amplifiers and the analog-to-digital converters from the power unit and the connecting unit.

2. The system according to claim 1, wherein each acquisition system comprises a plurality of terminals each connected to a group of electrode pairs of said acquisition system and arranged to collect said analog electric potentials picked up by the first and second electrodes of said group, and a relay connected to said terminals of said acquisition system and to the central system, said relay comprising said connecting unit and said power unit, wherein the operational amplifiers and the analog-to-digital converters of each acquisition system are provided in the relay and/or in the terminals of said acquisition system, wherein the relay of each acquisition system is arranged to galvanically isolate said operational amplifiers and said analog-to-digital converters of said acquisition system from its power unit and from its connecting unit.

3. The system according to claim 1, wherein each terminal of each acquisition system is arranged to transmit the analog electric potentials that it collects to the relay of said acquisition system, wherein the relay of each acquisition system comprises a plurality of acquisition stages each connected to at least one of the terminals of said acquisition system to receive said collected analog electric potentials and comprising at least an operational amplifier and an analog-to-digital converter to measure said differences in potential and convert said differences in potential into digital signals, each acquisition stage being connected to the connecting unit and the power unit while being galvanically isolated from said power unit and its connecting unit.

4. The system according to claim 1, wherein each acquisition stage of the relay of each acquisition system is connected to a plurality of terminals of said acquisition system to receive said analog electric potentials collected by said terminals, said stage comprising a multiplexer arranged to multiplex said first analog electric potentials collected by said terminals.

5. The system according to claim 2, wherein each terminal of each acquisition system comprises at least an operational amplifier to measure said differences in potential between the analog electric potentials that it collects and to transmit said differences in potential to the relay of said acquisition system, and wherein the relay of each acquisition system comprises a plurality of acquisition stages each connected to at least one of the terminals of said acquisition system to receive said differences in analog electric potentials, each acquisition stage being connected to the connecting unit and the power unit while being galvanically isolated from said power unit and its connecting unit.

6. The system according to claim 2, wherein the connecting unit comprises a microcontroller arranged to serialize the digital signals converted by the analog-to-digital converters and transmitted by each of the acquisition stages to the connecting unit into a single digital signal and to transmit said single digital signal to the central system.

7. The system according to any claim 1, wherein the central system is connected to each acquisition system by a data transmission network, wherein the central system is arranged to transmit to each acquisition system signals containing electric power via the data transmission network, and wherein the connecting unit is arranged to transmit said digital signals to the central system via said data transmission network, and wherein the power unit is arranged to extract said electric power from the signals received from the central system via the data transmission network and to transmit said extracted electric power to the operational amplifiers and to the analog-to-digital converters.

8. The system according to claim 1, wherein the connecting unit of each acquisition system comprises a coupler arranged to transmit the digital signals converted by the analog-to-digital converters of said acquisition system to the connecting unit, the coupler being arranged to galvanically isolate said analog-to-digital converters from the connecting unit.

9. The system according to claim 1, wherein each acquisition system comprises two rechargeable electric batteries and a switching system connected to said electric batteries, to the power unit, to the operational amplifiers and to the analog-to-digital converters of said acquisition system, the power unit of said acquisition system comprising a control unit of said switching system arranged to simultaneously: connect one of the electric batteries to the operational amplifiers and to the analog-to-digital converters of said acquisition system and disconnect said electric battery from the power unit; and disconnect the other electric battery from the operational amplifiers and from the analog-to-digital converters and connect said electric battery to the power unit.

10. The system according to claim 1, wherein the electric energy source of the central system comprises a photovoltaic panel.

Description

[0070] The present invention will now be described using examples that are purely illustrative and in no way limit the scope of the invention, and the accompanying drawings in which the different figures show:

[0071] FIG. 1 shows diagrammatically and in part a system for electrophysiological analysis of plants according to an embodiment of the invention;

[0072] FIG. 2 shows diagrammatically and in part an example of deployment in a field of the system for electrophysiological analysis of plants in FIG. 1;

[0073] FIG. 3 shows diagrammatically and in part an embodiment of the central system of the system for electrophysiological analysis of plants in FIG. 1;

[0074] FIG. 4 shows diagrammatically and in part an embodiment of a relay of the system for electrophysiological analysis of plants in FIG. 1; and

[0075] FIG. 5 shows diagrammatically and in part a diagrammatic view of the relay in FIG. 4.

[0076] In the description that follows, elements that are identical by structure or by function appearing in the different figures retain, unless stated otherwise, the same reference numerals.

[0077] FIG. 1 shows diagrammatically and in part a system for electrophysiological analysis 1 of a plurality of plants P according to an embodiment of the invention.

[0078] The system 1 is intended to be deployed in an agricultural field or in a glasshouse for measurements of analog electric signals emitted by the plants cultivated in said field or in said glasshouse to be carried out autonomously and continuously.

[0079] An example has therefore been shown in FIG. 2 of deployment of the system 1 in FIG. 1 in a field C made up of a plurality of parcels PC each comprising a plurality of plants P. As will be described, the system 1 allows the measurement of hundreds of said plants P spread over different parcels PC extending over a vast area of the field C to be carried out autonomously, in other words without the system 1 requiring an external energy source, and continuously for days or even weeks.

[0080] The system 1 comprises a plurality of acquisition systems 2 each connected to the same central system 6. In the example in FIG. 2, the system 1 comprises four acquisition systems 2, each the same as the others.

[0081] Each acquisition system 2 comprises a plurality of pairs of first electrodes 21 and of second electrodes 22, each pair being connected to one of the plants P. For example, the first electrode 21 is connected in the region of an upper portion of the stem of a plant P to be in contact with the phloem and the second electrode 22 is connected in the region of a lower portion of the stem of said plant P, also to be in contact with the phloem. In the example in FIG. 2, each acquisition system 2 comprises 128 pairs of electrodes 21 and 22.

[0082] Each first electrode 21 picks up a first analog electric potential P1 and each second electrode 22 picks up a second analog electric potential P2.

[0083] Each acquisition system 2 comprises a plurality of terminals 23 each connected to a group of electrode pairs 21 and 22. In the example in FIG. 2, each acquisition system 2 comprises sixteen terminals 23, each produced in the form of a terminal block to which eight pairs of electrodes 21 and 22 are connected, the terminal block thus collecting the first and second analog electric potentials P1 and P2 picked up by said eight electrodes.

[0084] Each acquisition system 2 comprises a relay 24 connected to the different terminals 23. As will be described below, each relay 24 comprises a plurality of operational amplifiers intended to measure the differences in potential between the first and second analog electric potentials P1 and P2 picked up by each pair of electrodes 21 and 22 of said acquisition system 2, as well as a plurality of analog-to-digital converters intended to convert said differences in potential into digital signals.

[0085] Each relay 24 further comprises a unit for connecting to a data transmission network to be connected to the central system 6 and to be able to transmit said digital signals to said central system 6. It will therefore be seen, with reference to FIG. 2, that the analysis system 1 is a network of sensors formed by the plants P, having a star topology around the central system 6, each acquisition system 1 having a tree topology of which the root is formed by the relay 24 and of which the endings are formed by the plants P. It will be seen that the number of relays 24 and terminals 23 described in FIG. 2 is an example, and a different, in particular a greater, number of relays and terminals may be envisaged without departing from the scope of the present invention. Similarly, adding concentrators between each relay 24 and the terminals 23 in order to increase the number of measurement points in the same zone of the field C, or alternatively adding extenders in order to reach parcels that are distant from the central system 6 may be envisaged.

[0086] As will be described below, the central system 6 comprises a computer server with an embedded memory in which are stored the different digital signals transmitted by the relays 24, which signals may then be processed in situ or alternatively reserved for subsequent processing. Moreover, to obtain an analysis system that can carry out measurements autonomously and continuously for a long period, the central system 6 comprises an electric energy source 8 that allows electric power to be supplied to the operational amplifiers and to the analog-to-digital converters of the relays 24. In the example in FIG. 2, the electric energy source 8 comprises a photovoltaic panel. Each relay 24 therefore comprises a power unit intended to receive said electric power transmitted by the central system 6 and to transmit said electric power to the operational amplifiers and to the analog-to-digital converter of said relay 24.

[0087] A preferred embodiment of the central system 6 of FIG. 1 and FIG. 2 will now be described with reference to FIG. 3.

[0088] As described previously, the central system 6 comprises a low-consumption, network-attached-storage (NAS) computer server 61, housing a plurality of hard disks 62 forming said memory of the central system 6. The system 1 also comprises a photovoltaic panel 8 associated with a linear low-dropout (LDO) voltage regulator 81 which regulates the electric power generated by the photovoltaic panel to supply electric voltage of a constant value to the server 61. Adding one or more electric batteries, connected on the one hand to the server 61 via a switching unit and on the other hand to the regulator 81 via a charge regulator, may be envisaged. In this case, a control unit may control the switching unit and the charge controller so as to allow the server 61 to be supplied directly in the diurnal period by the photovoltaic panel 8 and the electric battery or batteries to be charged, in which case supplying 61 the server by the electric batteries is not allowed, and so as to allow the server 61 to be supplied in the nocturnal period by the electric batteries.

[0089] The server 61 also has an embedded PoE network switch 63 to exchange data with the relays 24 of the acquisition systems 2 and in particular to receive the digital signals transmitted by said relays 24, and to be able to transmit the electric power generated by the photovoltaic panel 8 and the voltage regulator 81 to the operational amplifiers and to the analog-to-digital converters of said relays 24.

[0090] The relay 24 of each acquisition system 2 is thus connected to a port of said network switch 63 by an Ethernet cable 5, in other words a cable comprising for pairs of twisted wires, the data transmitted by the relays 24 or by the server 61 passing through two of the pairs and the electric power passing through the other two pairs.

[0091] A preferred embodiment of a relay 24 of an acquisition system 2 intended to be connected to the central system 6 of FIG. 3 will now be described with reference to FIG. 4 and FIG. 5.

[0092] The relay 24 comprises a plurality of acquisition stages 25 intended to receive the analog electric potentials P1 and P2 transmitted by the terminals 23, each comprising a plurality of operational amplifiers and analog-to-digital converters to measure the differences in potential and to convert said differences in potential into digital signals and a connecting stage 26 to which all said acquisition stages 25 are connected. Said connecting stage 26 comprises said connecting unit 51 which allows said digital signals to be transmitted to the central system 6 via the Ethernet cable 5 and said power unit 52 which allows the electric power transmitted by the central system 6 to be extracted from said Ethernet cable for distribution to the operational amplifiers and to the analog-to-digital converters of the acquisition stages 25. FIG. 4 therefore shows an overall view of a relay 24 while FIG. 5 describes diagrammatically one of the acquisition stages 25 and the connecting stage 26.

[0093] In the example in FIG. 4 and FIG. 5, each acquisition stage 25 is connected by a plurality of multiple coaxial cables to four terminals 23 to receive eight pairs of analog electric potentials P1 and P2 from each of said terminals. It will be observed that in the example described each second electrode 22 is connected to a common reference electric potential PR and in particular a ground of the acquisition stage 25 to which said second electrode 22 is connected, such that each second analog electric potential P2 is substantially equal to said common reference electric potential PR.

[0094] Each acquisition stage 25 comprises a multichannel multiplexer 27 of which the inputs are connected via the terminals 23 to the first electrodes 21. The multiplexer 27 is thus arranged to multiplex the first electric potentials P1 picked up by the first electrodes 21 and transmitted by the terminals 23. Each acquisition stage 25 therefore processes sequentially the first electric potentials P1 transmitted by the terminals 23, all the first electric potentials P1 transmitted by each terminal 23 being processed over the same multiplexing period.

[0095] Each acquisition stage 25 also comprises a multichannel analog-to-digital converter 3 comprising a plurality of operational amplifiers 31, each arranged to receive one of the outputs of the multiplexer 27, in this case a first analog electric potential P1 acquired by one of the first electrodes 21 and transmitted by one of the terminals 23, and said common reference electric potential PR and to measure the difference in electric potential between said first electric potential P1 and the common reference electric potential PR. In the example described, each operational amplifier 31 is a low-noise programmable gain amplifier (PGA), of which the gain may be programmed to a value of up to 24 while the average noise level introduced by the signal amplified by the amplifier does not exceed a value of substantially 2 μV for said gain of 24.

[0096] The multichannel analog-to-digital converter 3 also comprises a plurality of delta-sigma elementary analog-to-digital converters 32 each connected to the differential output of one of the operational amplifiers 31 to convert the difference in electric potential measured by said operational amplifier 31 into a digital signal. In the example described, each delta-sigma converter 34 is arranged to sample the difference in electric potential, for example at a sampling frequency of 250 Hz, so as to obtain a digital signal coded over 24 bits. This combination of low-noise PGA and delta-sigma converters allows an effective number of bits of at least 19 to be obtained when the PGA gain is fixed at 24. In this way, the digital signal obtained at the output of the elementary converter 32 has a particularly satisfying resolution, given the voltage level observed for the first electric potentials picked up by the electrodes 21. It should be noted that the sampling frequency may advantageously be modulated, in particular depending on the required recording period.

[0097] Finally, each acquisition stage 25 comprises a microcontroller 28 arranged to serialize the digital signals converted by each of the elementary converters 32, such that said acquisition system 25 is connected to the connecting stage 26 by a single channel over which said serialized digital signals pass. Similarly, the connecting stage 26 comprises a microcontroller 53 arranged to serialize the digital signals transmitted by all the acquisition stages 25. In the example described, all the components of each acquisition stage 25 are supported by the same printed circuit card, the acquisition stages 25 and the connecting stage therefore being stacked and housed in the same housing 29. All said elements therefore form a compact and autonomous assembly.

[0098] As can be seen, the connecting stage 26 of each relay 24 is arranged to galvanically isolate the acquisition stages 25 from the connecting and power units 51 and 52.

[0099] In the example described, the connecting stage 26 comprises an RJ45 connecter 41 to which the Ethernet cable 5 that connects said connecter to the central system 6 is connected.

[0100] To galvanically isolate the different components of the connecting stage 26 from other relays 24 and other sensors that may be connected to the central system 6 and to extract said electric power transmitted by the central system 6 via the Ethernet cable 5, the connecting stage 26 comprises a divider 42 comprising a plurality of isolation transformers, each connected via the connecter 41 to one of the twisted pairs in the region of the primary or secondary winding thereof. In FIG. 5, only the transformers connected to the twisted pairs transporting the electric power have been shown. The divider 42 is thus arranged to extract the electric power passing through the cable 5 from the windings of said transformers.

[0101] The connecting unit 51 comprises an interface 43 that allows the signals received from the cable 5 and the divider 42 to be converted into interpretable digital data and reciprocally the digital signals coming from the serializer 53 into signals that can be transmitted via the divider 42 and the connecter 41 over the cable 5.

[0102] The connecting unit 51 comprises a control unit 44 connected to the interface 43 arranged in particular to process the signals received from the cable 5.

[0103] The connecting unit 51 comprises an optocoupler arranged to transmit the digital signals coming from the serializer 53 to the control unit 44 while maintaining galvanic isolation between the control unit 44 and said serializer 53 and therefore the acquisition stages 25.

[0104] The power unit 52 comprises two rechargeable electric batteries 71 and 72 arranged, on the one hand, to supply the acquisition stages 25 with electricity and in particular the multichannel analog-to-digital converters 3, and on the other hand, to define the reference electric potential P.

[0105] The power unit 52 comprises an electric power converter 46 arranged to receive the electric power extracted from the divider 42 and convert said power into electric power suitable for charging the electric batteries 71 and 72.

[0106] The batteries 71 and 72 are therefore connected, on the one hand, to the power converter 46 and, on the other hand, to the acquisition stages by two switching devices 73 and 74 controlled simultaneously by a control unit 75 of the power unit 52.

[0107] The control unit 75 therefore controls the first switching device 73 so as to only allow the transmission of the electric supply power converted by the power converter 46 to one of the electric batteries, the battery 71 in the example in FIG. 5, in order to charge said battery. At the same time, the control unit 75 controls the second switching device 74 so as to only allow the transmission of the electric power contained in the other electric battery, the battery 72 in the example in FIG. 5 to the acquisition systems 25 for the electric supply thereof and the supply of the reference electric potential P2. This is because the inputs of the analog-to-digital converter 3 intended to receive the second analog electric potentials are connected via the second switching device 74 to the ground of said battery 72 supplying said acquisition stages 25.

[0108] In other words, the control unit 75 controls the switching devices 73 and 74 such that it is impossible for the battery 71 being charged to supply the acquisition stages 25 with electricity and such that it is impossible for the battery 72 supplying acquisition stages 25 and supplying the reference potential P2 to be charged by the power converter 46.

[0109] It can therefore be seen from FIG. 5 that, because of the switching devices 73 and 74 and the optocoupler 45, the reference potential P2 allowing the digital signals to be generated is independent of any disturbance that could occur on the Ethernet cable 5 and in particular any disturbance of the ground of the electric supply passing through said cable.

[0110] It should be noted that the analysis system 1 may comprise a digital processing module for the digital signals stored in the memory of the server 61, which is arranged to implement one or more methods of processing said digital signals in order to determine the physiological state of the plants P. Although not limiting, the processing module may be arranged to obtain a spectrum from each digital signal (for example by means of a Fourier transform or by wavelet decomposition) and to determine one or more spectral power indicators from said spectrums, then to implement methods for analyzing variations in said indicator(s) in order to determine the physiological state of the plants P. Said digital processing module may be embedded in the server 61 or may be remote from the server 61.

[0111] The description above explains clearly how the invention allows the objects set to be achieved, in particular by proposing a system for electrophysiological analysis of plants comprising a plurality of measurement points organized in a star architecture around a central system.

[0112] In any event, the invention is not limited to the embodiments specifically described in this document, and extends in particular to all equivalent means and to any technically possible combination of said means. Provision may be made in particular for the operational amplifiers and/or the analog-to-digital converters to be arranged in the region of the terminals of the acquisition systems, so as to render negligible the losses induced by the length of the entirety of the cables connecting the electrodes to the central system. Other embodiments may also be envisaged that allow the electric power from the photovoltaic panel to be transmitted to the relays of the acquisition systems, in particular by using concentrators and/or PoE injectors remote from the server of the central system. Replacing one or more of the terminals and/or relays by a sensor suitable for measuring an environmental parameter of the camp may also be envisaged. Not connecting the second electrodes to the same common reference electric potential and adding a second multiplexer to the acquisition stages could also be envisaged to allow the second analog electric potentials picked up by said second electrodes to be multiplexed.