Plant electrophysiological analysis system

Abstract

A plant electrophysiological analysis system (P) (1, 10), comprising: a first acquisition device (2) including at least one first electrode (21) intended to be connected to a plant to capture a first analog electrical potential (P1), the first acquisition device being arranged to generate a digital signal (S21) from said first analog electrical potential; a connection unit (4) arranged to transmit and receive signals to and from a data transmission network (5), respectively, the connection unit being arranged to transmit said digital signal to said data network and to extract electrical power (P1) from the signals received from the data transmission network, said electrical power being intended to power the first acquisition device. Figure to be published with the abbreviation: Fig. 1

Description

Title of the invention: Electrophysiological analysis system for plants

[0001] The invention relates to the field of electrophysiological analysis of plants. More specifically, the invention relates to a system for electrophysiological analysis of several plants.

[0002] It has been observed that plants emit electrical signals, particularly in the form of action potentials, reflecting their physiological state. By measuring these electrical signals using electrodes and analyzing them, it is thus possible to determine the physiological state of a plant more quickly and reliably than by direct observation means. In addition, if a stress or disease situation is detected, it is also possible to propose, immediately and automatically, corrective actions to remedy it.

[0003] However, existing electrophysiological plant analysis systems are designed for laboratory use and are not suitable for agricultural use. Indeed, the known systems are based, on the one hand, on an electrical signal acquisition system allowing these signals to be digitized for processing and, on the other hand, on a module for processing these digitized signals implementing, in particular, statistical analysis methods. It is therefore necessary to acquire a plurality of electrical signals simultaneously, over long periods. Thus, for agricultural use, it is necessary to install several acquisition devices in a field.This multiplicity of acquisition systems therefore requires the use of a multitude of power cables to electrically supply each of the acquisition devices and data transmission cables to enable the transmission of digitized signals to the processing module. The number of cables thus required is detrimental to the robustness of the system and its simplicity of installation and use.

[0004] The present invention is placed in this context and thus aims to remedy the drawbacks cited, by proposing a system for electrophysiological analysis of plants which is robust and simple to install and use.

[0005] For these purposes, the invention relates to a system for electrophysiological analysis of plants, comprising: a. a first acquisition device comprising at least one first electrode intended to be connected to a plant to capture a first analog electrical potential, the first acquisition device being arranged to generate a digital signal from said first analog electrical potential; b. a connection unit arranged to transmit and respectively receive signals to, respectively from a data transmission network, the connection unit being arranged to transmit to said data network said digital signal and to extract electrical power from the signals received from the data transmission network, said electrical power being intended to electrically supply the first acquisition device.

[0006] It is understood that, thanks to the invention, it is possible to share within a single cable the functions of electrical power supply and data transmission. Consequently, the number of cables necessary for the operation of the analysis system can be reduced, which simplifies the installation and use of this system while increasing its robustness, in particular by reducing the number of connectors necessary.

[0007] Advantageously, the connection unit comprises a connector to be connected by a cable of a data transmission network, for example of the Ethernet type, implementing an electrical power transmission functionality, for example of the POE (Power Over Ethernet) type. Such a cable of this type of data transmission network comprises at least two wires, for example four twisted pairs of wires in the case of an RJ-45 type Ethernet cable, the data passing through at least one of the wires, in particular by at least two wires, the data being transmitted by the potential difference on the two wires, and the electrical power by at least two wires, in particular by at least two pairs of wires, one of the pairs providing a negative pole for said electrical power and the other of the pairs providing a positive pole for said electrical power.In one example, the pair of wires transmitting the data may be one of the pairs of wires transmitting one of the poles for said electrical power. Alternatively, the pair of wires transmitting the data may be a separate pair of wires from the pairs of wires transmitting the poles for said electrical power.

[0008] In one embodiment of the invention, the connection unit comprises a divider comprising at least two transformers arranged to transmit and / or receive signals from the data transmission network, the divider being arranged to extract said electrical supply power from said transformers. These may for example be isolation transformers. Where appropriate, one of the transformers may be intended for an uplink for transmitting data to the first acquisition device, the primary winding of this transformer being intended to be connected to one of the wires, for example to a twisted pair of wires, of the data transmission network cable. The other of the transformers may be intended for a downlink to transmit the digital signal generated by the first acquisition device to the data transmission network, the secondary winding of this transformer being intended to be connected to another of the wires, for example to another twisted pair of wires, of the cable of the data transmission network. Advantageously, the connection unit is arranged to extract the electrical power from the primary winding of the uplink transformer and from the secondary winding of the downlink transformer.

[0009] Advantageously, the connection unit comprises an interface for analog / digital conversion and modulation / demodulation of the digital signal generated by the first acquisition device and of the signals received from the data transmission network. Said interface may be arranged between the divider and the first acquisition device. Modulation of a digital signal is understood to mean the transposition of this digital signal onto a carrier type signal to transport the information of this digital signal.

[0010] Advantageously, the connection unit comprises a coupler arranged to transmit the signals received from the data transmission network to the first acquisition device and to receive the digital signal generated by the first acquisition device, the coupler being arranged to galvanically isolate the first acquisition device from the connection unit. For example, the coupler may be an optocoupler. It has indeed been found that the electrical power passing through the data transmission network, and in particular its ground, undergoes disturbances, for example depending on the load applied to the data transmission network. These disturbances can adversely influence the acquisition of the first electrical potential by the first electrode or the generation of the digital signal by the first acquisition device. The use of a contactless coupler thus makes it possible to avoid disturbing the acquisition of the digital signal..

[0011] In one embodiment of the invention, the system comprises a rechargeable electric battery arranged to electrically power the first acquisition device. Where appropriate, the connection unit is arranged to charge said electric battery using said electric power. For example, the connection unit may comprise a power stage, in particular an electric power converter, arranged to receive said extracted electric power and to convert it into an electric power suitable for charging the electric battery.

[0012] Advantageously, the system may comprise two rechargeable electric batteries and a switching system connected to said electric batteries, to the connection unit and to the first acquisition device. Where appropriate, the connection unit comprises a control unit for said switching system arranged to simultaneously: a. connecting one of the electric batteries to the first acquisition device and disconnecting this electric battery from the connection unit; and b. disconnect the other electric battery from the first acquisition device and connect this electric battery to the connection unit.

[0013] In other words, the control unit authorizes the electrical power supply of the first acquisition device by one of the electric batteries and prohibits the charging of this electric battery by means of said electrical power and simultaneously prohibits the electrical power supply of the first acquisition device by the other of the electric batteries and authorizes the charging of this electric battery by means of said electrical power. This characteristic makes it possible to create an isolation between the connection unit, in which the disturbances of the electrical power passing over the data transmission network are present and the acquisition device, which can thus acquire the first electrical potential and generate the digital signal without being disturbed.

[0014] For example, the switching system comprises a first switching device connected to the connection unit and to said electric batteries so as to connect the connection unit selectively to one or other of the batteries and a second switching device connected to said electric batteries and to the first acquisition device so as to connect the first acquisition device selectively to one or other of the batteries, the control unit being arranged to simultaneously control the state of the first and second switching devices so that said electric power is transmitted to one of the batteries and the first acquisition device is powered by the other of the batteries.In other words, the first switching device allows the recharging of one of the batteries exclusively while the second switching device allows the power supply of the first acquisition device exclusively by the other of the batteries.

[0015] If desired, the system may comprise one or more capacitors arranged to deliver electrical power, during their discharge, to the first acquisition device, during changes of state of the switching devices.

[0016] Advantageously, the first acquisition device comprises an analog-digital converter provided with a first input connected to the first electrode to receive the first analog electrical potential, the analog-digital converter being arranged to measure the potential difference between the first analog electrical potential received and a reference electrical potential and to convert this measured potential difference into a digital signal, said reference electrical potential being obtained by means of the electric battery powering the acquisition device. The reference electrical potential may in particular be obtained by means of the electric battery authorized by the switching system to power the first acquisition device.

[0017] If desired, the or each first input connected to the or one of the first electrodes is associated with a filter arranged to filter the first analog electrical potential captured by this first electrode. The or each of the filters may comprise an analog smoothing filter and / or a filter for protection against electrostatic discharges.

[0018] Advantageously, the first acquisition device comprises a second electrode intended to be connected to said plant, wherein the analog-digital converter is provided with a second input connected to said electrode, the second input being connected to the ground of said battery powering the acquisition device. According to one example, the pair of first and second electrodes can be connected to the plant so as to measure a linear electric field generated by the superposition of the transient depolarizations of the membranes of the leaf cells and / or by the ion exchanges at the level of the root system. For example, each of the first and second electrodes can be connected to the stem of the plant to be in contact with the phloem or alternatively, one of the electrodes can be connected to the stem of the plant and the other of the electrodes can be connected to an underground bulb of the plant.

[0019] If desired, the first acquisition device comprises a plurality of first electrodes, each intended to be connected to a separate plant to capture a first analog electrical potential. If necessary, the analog-to-digital converter is a multi-channel analog-to-digital converter provided with a plurality of first inputs each connected to one of the first electrodes to receive one of the first analog electrical potentials, the multi-channel analog-to-digital converter being arranged to measure the potential difference between each first analog electrical potential received and said reference electrical potential and to convert each measured potential difference into a digital signal.If desired, the first acquisition device may comprise a plurality of second electrodes each intended to be connected to one of said separate plants and the multi-channel analog-to-digital converter comprising a plurality of second inputs each connected to one of the second electrodes, each second input of the multi-channel analog-to-digital converter being further connected to said common reference electrical potential.

[0020] Preferably, the analog-to-digital converter comprises an operational amplifier, the operational amplifier being arranged to receive the first analog electrical potential and said reference electrical potential, the analog converter comprising an analog-to-digital converter elementary delta-sigma connected to the output of the operational amplifier. A connection between the output of an operational amplifier and an elementary delta-sigma analog-to-digital converter is understood to mean both a single connection between a single-output amplifier and the converter through which the signal amplified by the amplifier passes, and a double connection between a differential-output amplifier and the converter, where the amplified signal is obtained by the difference between the signals passing through each of the lines of the double connection.

[0021] For example, the operational amplifier may be a low-noise programmable gain amplifier (also called a PGA). Where appropriate, the operational amplifier may be arranged to have a gain of at most 24 and to introduce noise whose average level is less than 5 pV and in particular substantially 0.1 pV in the case of an amplifier with a gain of 24. Advantageously, the elementary delta-sigma analog-digital converter is arranged to have a sampling rate greater than 50 SPS (sample per second) or 50 Hz, or even greater than 250 SPS or 250 Hz, and to convert a signal received at the input into a digital signal coded on 24 bits.Where appropriate, the unitary assembly formed by an operational amplifier and an elementary delta-sigma analog-to-digital converter is arranged to have an effective number of bits (also called ENOB, from the English Effective Number Of Bits) of at least 16, and in particular at least 19 for an amplifier gain of 24 and for a sampling rate of 250 SPS. This combination is particularly suitable for the electrophysiological analysis of plants insofar as the electrical potential differences from the operational amplifiers are low-amplitude analog signals (of the order of a microvolt) which can be amplified by the amplifier while introducing little noise and distortion, thanks to a low gain, and which nevertheless be converted by the converter into digital signals with high resolution (of the order of a nanovolt).

[0022] Advantageously, the first acquisition device comprises a housing in which the analog-digital converter is arranged, the connection unit also being arranged in said housing.

[0023] Advantageously, the electrophysiological analysis system comprises a module for digital processing of the digital signal generated by the acquisition device and transmitted over the data transmission network by the connection unit.

[0024] Advantageously, the processing module can be arranged to implement one or more methods for processing the generated digital signal to determine a physiological state of the plant. It has in fact been observed that the potential differences thus measured and therefore the converted digital signals exhibit variations which are functions of the physiological state of the plant, and in particular of its sunshine, its water stress, its thermal stress, etc. These variations are variations of certain frequency components of these converted digital signals, and in particular variations of low amplitudes of high frequency components.

[0025] The processing module may be arranged to carry out a spectral analysis of the digital signal. For example, the processing module may be arranged to obtain a spectrum from the digital signal (for example by means of a Fourier transform or by a wavelet decomposition) and to determine one or more spectral power indicators from this spectrum, and in particular one or more indicators chosen from the following indicators: a. a spectral edge frequency (also called Spectral Edge Frequency or SEF), namely a frequency below which 95% of the total spectral power is concentrated; b. a median frequency (also called in English: Median Edge Frequency or MEF), namely a frequency below which 50% of the total spectral power is concentrated; c. a power index, namely the total spectral power contained in a given frequency band, in particular a power index in the frequency bands known as beta (>0.5 Hz), alpha (0.3-0.4 Hz), theta (0.1-0.2 Hz) and delta (0-0.1 Hz); d. power index ratios, including a ratio of the delta power index and the theta power index; e. spectral entropy (also called Power Spectrum Entropy or PSE).

[0026] Advantageously, the processing module may implement methods for analyzing variations in this or these indicators, in particular to recognize a shift in the spectral frequency front and / or the median frequency according to a given model or a variation in a power index or a ratio of power indices according to a given model, or a variation in the spectral entropy according to a given model. It may, for example, be a method for classifying a variation in this or these indicators from a library of predetermined variation models, each predetermined variation model being associated with a given physiological state of a plant. Such a classification method may, for example, be implemented by a pattern recognition algorithm based on automatic learning for recognizing the models in said library of models.

[0027] The present invention is now described using examples which are solely illustrative and in no way limitative of the scope of the invention, and from the attached illustrations, in which:

[0028] [Fig-1] represents a system for electrophysiological analysis of plants according to a first embodiment of the invention;

[0029] [Fig.2] represents a system for electrophysiological analysis of plants according to a second embodiment of the invention.

[0030] In the following description, elements that are identical, by structure or by function, appearing in different figures retain, unless otherwise specified, the same references.

[0031] [Fig.l] shows schematically and partially an electrophysiological analysis system 1 of a plant P according to a first embodiment of the invention.

[0032] The system 1 comprises a first acquisition device 2 comprising a first electrode 21 and a second electrode 22. The plant P is thus connected to the pair of electrodes 21 and 22, the first electrode 21 being for example connected at the level of an upper section of the stem of the plant P to be in contact with the phloem and the second electrode 22 being for example connected at the level of a lower section of the stem of the plant P also to be in contact with the phloem.

[0033] In this embodiment, the first electrode El captures a first analog electrical potential PL

[0034] The first acquisition device 2 comprises an analog-digital converter 3 provided with a first input 31, connected to the first electrode to receive the first analog electrical potential PI and a second input 32 connected on the one hand to the second electrode 22 and on the other hand to a reference electrical potential P2. Each of the first and second inputs 31, 32 is associated with a filter (not shown) arranged to filter the first electrical potential PI intended to be received by this input 31, respectively the reference electrical potential P2.

[0035] The analog-to-digital converter 3 comprises an operational amplifier 33 arranged to receive the first analog electrical potential PI and said reference electrical potential P2 from the inputs 31 and 32 and to measure an electrical potential difference between this first potential PI and the reference electrical potential P2. In the example described, the operational amplifier 33 is a low-noise programmable gain amplifier, also called PGA (Programmable Gain Amplifier), whose gain can be programmed up to a value of 24 without an average level of the noise introduced into the signal amplified by the amplifier exceeding a value of substantially 2 pV for this gain of 24. The analog converter further comprises an elementary analog-digital converter 34 of the delta-sigma type connected to the differential output of the operational amplifier 33 to convert the measured electrical potential difference into a digital signal S21. In the example described, the delta-sigma type converter 34 is arranged to sample the electrical potential difference, for example at a sampling frequency of 250 Hz, so as to obtain a digital signal S21 coded on 24 bits. This combination of low-noise PGAs and delta-sigma type converters makes it possible to obtain an effective number of bits of at least 19 when the PGA gain is fixed at 24. In this way, the digital signal S21 obtained at the output of the elementary converter 5 has a particularly satisfactory resolution, taking into account the voltage levels observed for the electrical potential captured by the electrode 21.It should be noted that the sampling frequency can be advantageously modulated, in particular according to the desired recording duration.

[0036] The system 1 comprises a connection unit 4 for connecting the first acquisition device 1, via a data transmission network 5, to a digital processing module 6 of the digital signal S21, which is arranged to implement one or more methods for processing this digital signal S21 in order to determine a physiological state of the plant P. Without this being limiting, the processing module 6 may be arranged to obtain a spectrum from the digital signal S21 (for example by means of a Fourier transform or by a wavelet decomposition) and to determine one or more spectral power indicators from this spectrum, then to implement methods for analyzing the variations of this or these indicators in order to determine the physiological state of the plant P.

[0037] The system 1 also comprises two rechargeable electric batteries 71 and 72 arranged to, on the one hand, electrically power the first acquisition device 2, and in particular the analog-digital converter 3, and on the other hand, define the reference electric potential P2.

[0038] In the example described, the connection unit 4 is connected to the processing module 6 by a connector 41 to which is connected an RJ45 type cable 5 allowing connection to an Ethernet type network implementing an electrical power transmission functionality. For this purpose, the cable 5 comprises four pairs of twisted wires, the data transmitted on the network passing through two of the pairs and the electrical power passing through two other pairs.

[0039] In order to galvanically isolate the various components of the connection unit 4 from other equipment that can be connected to the network 5 and to extract the electrical power, the connection unit 4 comprises a divider 42 comprising a plurality of isolation transformers each connected, via the connector 41, to one of the twisted pairs at their primary or secondary winding. In [Fig.l], only the transformers connected to the twisted pairs carrying the electrical power have been shown. The divider 42 is thus arranged to extract the electrical power PA passing on the cable 5 from the windings of these transformers.

[0040] The connection unit 4 comprises an interface 43 making it possible to convert the signals received from the cable 5 and the divider 42 into interpretable digital data and, conversely, the digital signal S21 generated by the analog-digital converter 3 into a signal which can be transmitted, via the divider 42 and the connector 41, on the cable 5.

[0041] The connection unit 4 comprises a control unit 44 connected to the interface 43 arranged in particular to process the signals received from the cable 5.

[0042] The connection unit 4 comprises an optocoupler arranged to transmit the signals processed by the control unit 44 to the first acquisition device 2 and to transmit the digital signal S21 generated by the analog-digital converter 3 to the control unit 44, while maintaining galvanic isolation between the control unit 44 and the first acquisition device 2.

[0043] The connection unit 4 comprises an electrical power converter 46 arranged to receive the electrical power PA extracted from the divider 42 and convert it into an electrical power suitable for charging the electrical batteries 71 and 72.

[0044] The batteries 71 and 72 are thus connected, on the one hand, to the connection unit 4 and its power converter 46 and, on the other hand, to the first acquisition device 2 by two switching devices 81 and 82 controlled simultaneously by the control unit 44 of the connection unit 4.

[0045] The control unit 44 thus controls the first switching device 81 so as to authorize only the transmission of the supply power converted by the power converter 46 to one of the electric batteries, the battery 71 in the example of [Fig. 1], for the purpose of charging it. At the same time, the control unit 44 controls the second switching device 82 so as to authorize only the transmission of the electric power contained in the other of the electric batteries, the battery 72 in the example of [Fig. 1], to the first acquisition device 2, for the purpose of supplying it with electricity and providing the reference electric potential P2. Indeed, the second input 32 of the analog-to-digital converter 3 is connected, via the second switching device 82, to the ground of this battery 72 supplying the acquisition device 2.

[0046] In other words, the control unit 44 controls the switching devices 81 and 82 so that it is impossible for the battery 71 under charge to electrically supply the first acquisition device 2 and it is impossible for the battery 72 supplying the first acquisition device 2 and providing the reference potential P2 to be charged by the connection unit 4.

[0047] It can thus be seen from [Fig.l] that, thanks to the switching devices 81 and 82 and to the optocoupler 45, the reference potential P2 allowing the generation of the digital signal S21 is independent of any disturbance which may occur on the data transmission network 5 and in particular of any disturbance of the ground of this network.

[0048] It should be noted that in the example of [Fig.l], the first acquisition device 2 comprises a housing 23 in which the analog-digital converter 3, the connection unit 4, the batteries 71 and 72 and the switching devices 81 and 82 are arranged. All these elements thus form a compact and autonomous assembly, which can be connected to the data transmission network 5 and which can be electrically powered by a single cable.

[0049] Finally, although the example described in [Fig.l] only describes a single first acquisition device 2, it goes without saying that the analysis system 1 may employ a plurality of acquisition devices, each being similar to the first acquisition device 2 and being connected to one or more other plants, the digital signals converted by these devices all being transmitted to the processing module 6 to be processed there.

[0050] [Fig.2] schematically and partially describes an electrophysiological analysis system 10 according to a second embodiment of the invention.

[0051] This system 10 is similar, structurally and functionally, to the system 1 described in [Fig.l], with the exception of the characteristics described below.

[0052] In the example of [Fig.2], the first acquisition device 2 comprises a plurality of first electrodes 21 and a plurality of second electrodes 22, each connected to a plant P such that each plant P is thus connected to a pair of electrodes 21 and 22. Each plant P is thus connected to a pair of electrodes E1 and E2, the first electrode E1 being for example connected at an upper section of the stem of the plant P to be in contact with the phloem and the second electrode E2 being for example connected at a lower section of the stem of the plant P also to be in contact with the phloem. In this embodiment, each of the first electrodes E1 senses a first analog electrical potential PI.

[0053] The first acquisition device 2 comprises a multi-channel analog-to-digital converter 3 provided with a plurality of first inputs 31, each connected to one of the first electrodes 21, via a filter, so that each first electrical potential PI captured by one of the first electrodes 21 is simultaneously received by the converter 3. Equivalently, the converter 3 is provided with a plurality second inputs 32 connected to the second electrodes 22 and to the common reference electrical potential P2 obtained from the battery 71 or 72.

[0054] The converter 3 comprises a plurality of operational amplifiers 33, each amplifier 4 thus receiving the first analog electrical potential PI and the common reference electrical potential P2 and measuring an electrical potential difference between these potentials PI and P2.

[0055] The converter 3 also comprises a plurality of elementary analog-digital converters of the delta-sigma type 34, each elementary converter 34 being connected to the output of one of the amplifiers 33 to receive the electrical potential difference measured by this amplifier 33 and convert it into a digital signal S21, which is thus transmitted to the connection unit 4.

[0056] The preceding description clearly explains how the invention makes it possible to achieve the objectives it has set for itself, and in particular by proposing a system for electrophysiological analysis of plants provided with a unit for connection to a data transmission network which is capable of extracting electrical power passing through this network in order to electrically supply an acquisition device of the system. It is thus understood that the capacity of the connection unit to extract this electrical power from the data transmission network makes it possible to reduce the number of cables necessary for operating the system and therefore to make the system more robust and simpler.

[0057] In any event, the invention cannot be limited to the embodiments specifically described in this document, and extends in particular to all equivalent means and to any technically effective combination of these means.

Claims

Claims

1. System (1, 10) for electrophysiological analysis of plants (P), comprising: • a first acquisition device (2) comprising at least one first electrode (21) intended to be connected to a plant to capture a first analog electrical potential (PI), the first acquisition device being arranged to generate a digital signal (S21) from said first analog electrical potential;• a connection unit (4) arranged to transmit and respectively receive signals to, respectively from a data transmission network (5), the connection unit being arranged to transmit to said data network said digital signal and to extract an electrical power (PA) from the signals received from the data transmission network, said electrical power being intended to electrically power the first acquisition device in which the connection unit (4) comprises a divider (42) comprising at least two transformers arranged to transmit and / or receive signals from the data transmission network (5), the divider being arranged to extract said supply electrical power (PA) from said transformers.;

2. System (1, 10) according to the preceding claim, in which the connection unit (4) comprises an interface (43) for analog / digital conversion and modulation / demodulation of the digital signal (S21) generated by the first acquisition device (2) and signals received from the data transmission network (5).

3. System (1, 10) according to one of the preceding claims, in which the connection unit (4) comprises a coupler (45) arranged to transmit the signals received from the data transmission network (5) to the first acquisition device (2) and to receive the digital signal (S21) generated by the first acquisition device, the coupler being arranged to galvanically isolate the first acquisition device from the connection unit.

4. System (1, 10) according to the preceding claim, in which the coupler (45) is an optocoupler.

5. System (1, 10) according to one of the preceding claims, the system comprising a rechargeable electric battery (71, 72) arranged to electrically power the first acquisition device (2), in which the connection unit (4) is arranged to charge said electric battery by means of said electric power (PA).

6. System (1, 10) according to the preceding claim, the system comprising two rechargeable electric batteries (71, 72) and a switching system (81, 82) connected to said electric batteries, to the connection unit (4) and to the first acquisition device (2), the connection unit comprising a control unit (44) of said switching system arranged to simultaneously: • connect one of the electric batteries to the first acquisition device and disconnect this electric battery from the connection unit;; and • Disconnect the other of the electric batteries from the first acquisition device and connect this electric battery to the connection unit.

7. System (1, 10) according to the preceding claim, wherein the switching system (81, 82) comprises a first switching device (81) connected to the connection unit (4) and to said electric batteries (71, 72) so as to connect the connection unit selectively to one or the other of the batteries and a second switching device (82) connected to said electric batteries and to the first acquisition device (2) so as to connect the first acquisition device selectively to one or the other of the batteries, the control unit (44) being arranged to simultaneously control the state of the first and second switching devices so that said electric power is transmitted to one of the batteries and the first acquisition device is powered by the other of the batteries.

8. System (1, 10) according to one of claims 5 to 7, in which the first acquisition device (2) comprises an analog-digital converter (3) provided with a first input (31) connected to the first electrode (21) to receive the first potential analog electrical (PI), the analog-to-digital converter being arranged to measure the potential difference between the first received analog electrical potential and a reference electrical potential (P2) and to convert this measured potential difference into a digital signal (S21), said reference electrical potential being obtained by means of the electric battery (71, 72) powering the acquisition device.

9. System (1, 10) according to the preceding claim, in which the first acquisition device (2) comprises a second electrode (22) intended to be connected to said plant (P), in which the analog-digital converter (3) is provided with a second input (32) connected to said electrode, the second input being connected to the ground (P2) of said battery (71, 72) supplying the acquisition device.

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