GB2348010A

GB2348010A - Modular chemical sensing system with sensor array

Info

Publication number: GB2348010A
Application number: GB0005385A
Authority: GB
Inventors: Mark Philip Byfield; Jr Stanley Lester Hathcock; Andrew Charles Pike
Original assignee: Marconi Applied Technologies Ltd
Current assignee: Teledyne UK Ltd
Priority date: 1999-03-05
Filing date: 2000-03-06
Publication date: 2000-09-20
Anticipated expiration: 2020-03-06
Also published as: GB9916925D0; AU3173700A; JP2002539427A; WO2000054044A1; GB0005379D0; GB9905053D0; GB0005385D0; GB2348010B; EP1159609A1

Abstract

A chemical sensor system for at or on line monitoring of a product or process is based on a modular basis to give flexibility. The system is separated into sample handling modules 1 which acquire samples of the substance to be sensed, sensor modules 2 including an array of sensors, and processing modules 3 which derive information from the output of the sensor modules using pattern recognition. User interface modules 4 may also be incorporated. Many different sampling techniques, sensor technologies, and arrangements of modules are described. The system may be used in a wide range of industries, such as water quality monitoring and fermentation processes.

Description

2348010 P/61766.GBPMSD Chemical Sensor Systems This invention relates to

chemical sensor systems, and more particularly to systems for at - or on-line monitoring of a product or process.

Chemical sensor array systems for sensing in the liquid, gas or vapour phase, including as a sub-class those arrays sometimes referred to as electronic noses, have been successfully employed in laboratory instruments for the measurement of headspace volatiles. Typical applications include quality control of raw materials and final product, new product development and correlation with sensory panel data. All the instruments described to date, including those cornmercially available such as the EEV eNOSE 5000 and those developed through academic or industrial research programmes, have been stand-alone integrated systems aimed primarily for laboratory use. They are relatively large instruments, typical base unit diamensions being 0.5m x 0.45m x 0.4m and encompass a PC as a user interface for programming analysis runs and acquiring and displaying data.

At- and on-line instruments based on chemical sensor array technology (SAT) have been proposed for monitoring production processes. These have been envisaged as modified variants of the large laboratory instruments but with a simplified user interface and less functionality.

The term "at-line" as used in this specification is defined to mean that a monitoring instrument is located next to the detection point of interest, from which the sample can be introduced either manually or by automated means. Analysis of the product or process is 2 achieved from a discrete sample or batched samples. The term "on-line" is defined to mean that there is a physical connection between the monitoring system and the detection point, which allows the product or process to be monitored by discrete samples, batched samples or continuously. In on-line systems, sampling is automated. "In line" systems are a sub-set of on line systems.

According to the invention, there is provided a chemical sensor system for at or on-line monitoring of a product or process comprising: a sample handling module for acquiring a sample of a substance to be sensed, a sensor module including an array of sensors arranged to sense the sample; and a processing module for deriving information from the output of the sensor module using pattern recognition, The advantage of using monitoring technology in an at-line or on-line configuration is that it enables 'point of use' or in-situ measurement of a sample which in turn allows real-time monitoring of a product or process. A process to be monitored may involve one or more physical or chemical procedures used in the treatment, conversion or manufacture of an intermediate or final product. The process may be carried out at a fixed location or the product may be moved between locations during the process. In a manufacturing environment at-line or on-line monitoring allows rapid corrective action to be taken if there has been a deviation from normal or acceptable performance or quality in product or process. The delay in taking a sample for remote off-line analysis in a laboratory-based instrument is often unacceptable. At and on-line monitoring is therefore preferable in many areas of industry and also in enviroru-nents where the system is monitoring for hazardous conditions for example fire or generation of toxic vapours.

3 The invention offers significant advantages over previously proposed apparatus. The modular construction of the system permits optimisation of the system as a whole for a particular at or on-line monitoring function, as it enables easy adaptation of a system for a particular product or process line where monitoring may take place at one station of the line or at several distributed stations. For any given application of the system, optimum performance and maximum flexibility is readily achieved by suitable selection and implementation of modules. For example, the sample handling module may use at least one of the following techniques to acquire a sample: portable liquid, head space; sample vaporisation; liquid sparge; a probe, solid head space, direct insertion of an array of liquid phase chemical sensors into the sample or sample stream, gas line and ambient monitoring. Other techniques may be appropriate. Thus for a particular system, it is necessary to select a sample handling module using a technique appropriate to the substance to sensed, but other modules of the system may be common to another system in accordance with the invention used to monitor the product or process at a different stage of the manufacturing line, or even on a different line altogether.

Thus the invention provides significant advantages as it permits maximum flexibility in system design, optimised system performance and minimum manufacturing complexity, resulting in reliability and reduced costs. As each module comprises a separate physical unit, a variety of different modules based on different technologies or employing different functions may be made available in the same system. The modules may be constructed such that they are completely stand alone, or may include a mount arrangement, say, so that one module may be attached to another.

The chemical sensor system may provide information concerning the operation of a 4 production line or a process which can then be used in a control feedback system, in which data generated by the system is fed back to determine the settings of control hardware, for example, in a System Control and Data Acquisition (SCADA) system. Feedback may also be provided to the monitoring system itself, for example, to adjust sensor settings or sampling frequency.

As discussed above, first, considering the sample handling module, various techniques are available for acquiring a sample. A module using a liquid head space is suitable for monitoring ambient volatiles above a liquid sample. Liquid sparge comprises flushing a liquid sample with inert gas to release volatiles. A probe may comprise, for example, a flexible tube and pump to acquire a sample. In a solid head space, ambient volatiles are monitored above a solid sample. A gas line might be used in which a sample is drawn off from a gas stream, this being particularly suitable for processes involving fermentation. A sample handling module may use an ambient technique such as passive monitoring of the local environment, for example, for fire detection. Other techniques may be appropriate for other applications.

Where a sample is to be monitored in the liquid phase a sensor array may be inserted into the sample or sample stream.

The sample handling module may be adjusted so as to acquire a sample without operator intervention to give an automated procedure and samples may be taken at discrete time intervals or continuously. The module may be such that switching between discrete, batched and continuous sampling may take place depending on the particular time in a production process, location of which the sample is taken or for some other reason.

In one system, the sampling module includes means to introduce a calibration or reference sample. Alternatively, this may be provided at the sensor module. This allows calibration or checking of the sensor array performance.

Many different sensor technologies are available for incorporation in the sensor module. Advantageously, the sensor module includes a sensor array using at least one of the following types of sensor technology: mass sensitive sensor; electronic conductance or capacitance sensors; field effect sensors; calorimetric sensors; electrochemical sensors (for example, amperometric, potentiometric or conductimetric sensors); optochemical or photometric sensors; and biosensors. In fact any sensor which produces a useful output corresponding to a change in characteristic when a chemical is sensed may be suitable. Mass sensitive sensors may be for example those using bulk acoustic wave or surface acoustic wave techniques. Electronic conductance and capacitance sensors may be for example chemo resistors based on conducting polymer or metal oxide semiconductor materials. Calorimetric sensors may for example be pellistors. Electrochemical sensors are for example potentiometric cells. Infra red and fibre optic based techniques may be used in optochernical or photometric sensors. Biosensor and electrochemical sensors may be particularly suitable for liquid phase sensing.

A system in accordance with the invention may include a sensor array having sensors of one technology type only. In that case, the sensor environment can be specifically tailored for use with sensors of that type. In alternative arrangements, the sensor array includes sensors of a combination of different technology types. This gives increased sensitivity and/or discrimination in some cases, the particular combination being tailored to the substance to be 6 sensed.

The sensor array may include some features which give it a sample handling capability, for example, for accepting the sample from the sample handling module.

In one preferred embodiment, the processing module processes data related to the sample to format the data for the application of a pattern recognition (PARC) technique to it.

However, in other systems, the formatting aspect might be carried out in the sensor module.

The pattern recognition technique used in the processing module may use at least one of the following: a statistical method (for example, principal component analysis (PCA), or multiple discriminant analysis (MDA)); fuzzy logic; an artificial neural network; and a proprietary classifier algorithm. The technique or techniques adopted depend on the substance to be sensed and the use made by the system of information acquired via the monitoring procedure.

Means may be included in the system to provide in-built system diagnostics to derive test data or information from each module in turn, combinations of modules or the entire system to assess the performance and condition of individual modules or the system, This may involve supplying well-characterized test signals or test data to modules or the system and measuring the output against known or expected results. It may involve supplying test calibrants or reference chemical samples to the system. Such a diagnostic may be software based.

In one embodiment, at least one of the sample handling module, sensor module and processing module incorporates an integral user interface for communicating information to 7 and/or ftom. a user. Alternatively, or in addition, the system includes a user interface module. A user may be a human operator or a device, data store or some other non-human user.

In a preferred system, a user interface module includes means for presenting information to, and/or accepting input from, an operator. The module may include displays such as provided by a PC monitor, liquid crystal displays, LEDs or warning lights or may include aural information, for example, to give alarms. The operator may apply input to the system via a keyboard or a touch sensitive screen included in the user interface module. In other systems, the user interface module may comprise a communication line to provide, say, digital communication to factory or site networks. This may for example provide feedback to the manufacturing line in accordance with information gained via the monitoring procedure.

Alternatively, data may be logged for later analysis.

In one embodiment of the invention, at least one of the sample handling module, sensor module, processing module and user interface module comprises a plurality of sub-modules.

Thus, for example, a sub-module of the sensor module may include one type of sensor -technology and another sub-module another type of sensor technology. These are combined together to form the complete sensor module. This gives increased flexibility whilst still taking advantage of the modular construction of the system.

In an advantageous embodiment, there is included a plurality of at least one of the following types of module: sample handling module; sensor module; processing module and user interface module. Various combinations of multiple modules may be made depending on the particular application in which the system is being used. A system may include a set of 8 modules interconnected in a different configuration to another set of modules included in the system.

In one system, means are included for communicating with at least one of the modu!es, or between modules, via a wireless link, for example, one using microwave or RF communication.

The system may be arranged so that each module is located locally to the monitoring point or such that some are remotely located.

The system may comprise some or all of the following aspects distributed between the modules included in the system. The distribution of these functions depends on the particular system. The functions involved may for example be sample transfer (for example via manifolds, valves, mass flow controllers or pumps), sample conditioning (for example using filters or temperature control), sensor flow cell (for example, the sensor, sensor housing and temperature control), signal conditioning (for example involving generation of an electrical signal), signal communications (for example by transfer of analogue or digital signals) data acquisition (such as the collection of data points to represent signal information), pre processing (for example, averaging, electrical filtering, transformation and feature extraction), pattern recognition, classification and output of information to the user interface or process line. For example, the data acquisition may take place in the sensor module or in the processing module depending on how a particular system is designed.

The invention may be advantageously used in the applications listed below.

9 Water Industry & environmental such as: water treatment works intake protection) sewage / waste water treatment plant intake protection; waste water monitoring; process water monitoring, liquid effluent and discharges; refiigerant detection e. g. leaks; air analysis, malodour and industrial emissions.

Fermentation such as process monitoring; end point determination and prediction; detection of contamination; process efficiency optimisation,process deviation monitoring and detection of batch addition points.

Food and beverages such as raw material quality; natural products quality; detection of contaminants and taints; authenticity tests (e.g. orange juice concentrates); direct monitoring of processes such as, roasting, baking, pasteurising, fermentations, distillations, freezing, drying and freeze-drying.

Quality / status of intermediate products generated, environmental impacts and discharges, dosing in of additives / actives; blending; settling; final product quality, product stability; detection of taints and off-odours associated with packing materials, leaky packaging detection; monitoring of taints occuring during transport, product degradation or spoilage e.g bacterial, fungal, oxidation etc, product quality checks, authenticity checks, detection of genetically-modified foodstuffs and raw materials-, agricultual; detection of irradiated food; fruit ripening and supermarket checkout sensor systems for food products.

Petrochemicals, fine chemicals and pharmaceuticals such as identity confirmation (vessel contents vs label); QC tests (purity and grade); process monitoring such as distillation, cracking, synthetic procedures, catalytic conversions, and environmental impact and discharges, dosing additives, blending monitoring, formulation, grade assessment, product quality evaluation, product stability, organoleptic assessment and packaging such as leak detection (contents and odours), correct labelling vs content. leak detection (tankers, storage tanks, pipelines), fragrances and flavours, detection of additives to natural gas.

Medical, hygiene and microbial monitoring such as monitoring of body fluids e.g.

blood, urine, breath, secretions from skin and other organs, use thereof for clinical diagnosis, e.g. UTI detection by urine odour tests, clinical diagnosis from breath, e.g. diabetes, cancer, gastric ulcers, kidney damage, exposure to industrial / workplace chemicals from urine or breath monitoring. Skin volatiles as markers of industrial toxicity, bacteria e.g. coliforms from their volatile signatures (hygiene), anesthetic gas monitoring, animal health surveillance and forensic science applications.

Security such as drug detection / screening, explosives detection screening, fire detection / prediction systems based on vapour sensing, hardous / toxic materials.

Transport such as in-car environment monitoring such as analysis of exhaust gas, measurement of car interior components.

Household and personal care such as cosmetics, perfumery, fragrance dosing and control in detergents and aerosols.

Some ways in which the invention may be performed are now described with reference to the accompanying drawings in which:

Figure I schematically shows a system in accordance with the invention; Figures 2 to 12 schematically illustrate different systems in accordance with the invention-, Figures 13, 14 and 15 illustrate parts of another system in accordance with the invention-, and Figures 16 and 17 show results obtained using systems in accordance with the invention.

With reference to Figure 1, a chemical sensor system or SAT system comprises in one aspect, a sample handling module 1, a sensor module 2, a processing module 3 and a user interface module 4. Each of these modules comprises a discrete physical unit, separate from the remainder. In other embodiments, a separate user interface module may be omitted.

Connections are made between the modules depending on whether electrical or optical signals are to be transmitted or the sample of a substance for example between the sample handling module I and sensor module 2. Each module may incorporate one or more of the aspects described above. For example, in this system, the sensor module 2 may comprise an array of sensors of one technology type or a combination of technology types.

Some ways in which the system may be implemented are shown in the remaining 12 Figures in which, in each Figure, sample handling modules are referenced SH, sensor modules SM, processing modules PM and user interface modules UI.

With reference to Figure 2, three sample handling modules 5, 6 and 7 are distributed at different points along a manufacturing line and are arranged to acquire samples of a substance to be sensed at each location. The outputs of each of the sample handling modules 5, 6 and 7 are applied to a common sensor module 8 which senses the substance either simultaneously or sequentially from different sample handling modules to derive data concerning the substances at each location. This information is then transmitted to a processing module 9 which carries out pre-processing and pattern recognition so as to identify the quality and/or identity of the such a substances sampled by modules 5, 6 and 7. This information is then transmitted to a user interface module 10 for display to an operator. The operator then uses the information in controlling the manufacturing process.

Figure 3 illustrates another embodiment incorporating a single sample handling module 11, the output of which is transmitted in parallel to three sensor modules 12, 13 and 14 to increase discriminatory information. In this embodiment, each of the sensor modules 12, 13 and 14 employs are respective different technology, but this is not essential. The outputs of the sensor modules 12, 13 and 14 are applied to a processing module 15 for data analysis. In this arrangement, the output of the processing module 15 comprises a contr6l signal which is applied via user interface module 16, which consists of a data link, to provide automatic feedback to a manufacturing process.

With reference to Figure 4, as shown, a plurality of sample handling modules 17, 18 13 and 19 are connected to respect different sensor modules 20, 21 and 22. Each sample handling module and associated sensor module are located at the manufacturing line and their outputs are transmitted to a common processing module 23 remotely located therefrom. The output of processing module 23 is applied to a user interface module 24.

In Figure 5, another arrangement is shown. This system is a distributed configuration and requires at-line or on-line displays. Thus sample handling modules 25, 26 and 27 and associated sensor modules 28, 29 and 30 each have an associated user interface, consisting of a display, 31, 32 and 33 respectively, all of these modules being located at-line or on-line. A central processing module 34 is remotely located and arranged to receive information from sensor modules 28, 29 and 30, user interface modules 31, 32 and 33 and transmitting information in response.

Figure 6 illustrates another arrangement in which a first set of modules 35 is located at one point and a second set 36 at a another point giving a distributed system with local processing and local displays.

Figure 7 shows a distributed system having local processing with remote display capability.

Figure 8 illustrates a single point of measurement system having both local processing and local display capabilities.

Figure 9 shows an arrangement having local processing but a remote display.

14 Figure 10 shows a single point of measurement having both remote processing and a remote display.

Figure I I shows a single point of measurement with remote processing and a local display.

Figure 12 illustrates a system similar to that shown in Figure 5 but in which the user inter-face modules are omitted, with user interface functions being completely integral in the sensor modules. In this system also, the processing module 37 provides control signals to both the sample handling modules 38, 39 and 40 and the sensor modules 41, 42 and 43 to adjust their operation dependent on the data acquired from the samples. Control is also provided to the process line from the processing module 37 to a manufacture control system 44.

Figures 13, 14 and 15 illustrate parts of another system in accordance with the invention. The system includes a processor module 45, user interface module 46, sensor module 47 and sample handling module 48, as shown in Figure 13.

The processor module 45 includes a Single Board Computer (SBC) and a hard drive. The SBC has integrated onto it drives for various inputs/outputs. There is an ethernet connector providing a direct connection to a Local Area Network. There is also a connector to a flat panel display and a connector that can be used for button inputs to provide a user interface 46. There is also a communications port (RS485) that is used to connect to any sensor module 47 and/or sample handling module 48 incorporating an RS485 interface IC.

The sensor module 47 is shown in Figure 14 which only indicates electrical connections and does not indicate the physical connection to a sampler. The sensor array 49 may be in a housing 50 that is temperature controlled with tubing connections in order to pass samples (in the gas phase) over the sensors. Alternatively, the sensor array may analyse a sample in-line. The sensors are sensing their ambient. In this case temperature control is not necessary; however the functionality of temperature control is still present.

This redundancy of functionality is necessary for modularity.

There are three types of sensor which may be used in the sensor modules 47 in this embodiment, these being BAW (bulk acoustic wave), SAW (surface acoustic wave) and chemoresistive sensors. Because the sensor modules with these different technology types all use the same interface hardware and interface protocol they are inter- changeable without any hardware modifications.

The sample handling module is shown in Figure 15. Examples of the sample handling sensors 51 used in the current system are relative humidity, temperature and flow.

The sample handling hardware 52 includes a mass flow controller and valves. There are also connections from the interface electronics 53 to drive other hardware e.g. temperature control units, pumps. Again this is an example of redundancy being built in to provide modular systems. The module also includes a microcomputer 54 and RS 485 interface IC 55.

Sample handling for two different applications has been investigated, these being 16 fermentation monitoring and water quality monitoring.

In the case of fermentation, a vent line is located where a sample is released in the gas phase. The sample released from the vent line is passed through the sample handling hardware 48 and through the sensor module 47. There may be filters or condensers on the vent line prior to the sample handling module 48. If the flow rate from the vent line is high only a proportion of the flow is diverted through the system. Figure 16 gives a response profile for a five BAW sensor array measuring the headspace of a yeast fermentation using an on-line modular sensor array system.

For water quality monitoring, the water is passed through a sparger unit. A source of carrier gas is then connected to the sparger unit, which is bubbled through the liquid sample. Volatiles in the water are released to the carrier gas that is then passed through the sensor module. Figure 17 is a Multiple Discriminant Analysis (MDA) plot of data obtained on raw river water samples using an at-line modular sensor array system. Sensor array data from uncontaminated raw water prior to and subsequent to a pollution incident is shown on the root I versus root 2 MDA plot and is plotted as circles and squares respectively.

Polluted water was "detected" by virtue of its lower root 1 value and is represented on the plot by crosses.

The sensor signals in the sample handling module 48 are interfaced by electronics to the microcomputer 54, where they may be processed before being communicated to the processor module 45. Again an RS485 interface IC is used to ensure the signals from the 17 microcomputer are compatible with the multi-drop serial data link. Signals from the processor module 45 have to be passed to the sample handling module 48 in order that system can be switched between different states or to change particular parameters e.g. flow rate.

There is a protocol to ensure that two way communication can occur between the processor module 45 and any sensor 47 or sample handling module 48 on the RS485 bus.

Having the following protocol allows any number of modules to be interconnected up to the physical limit of the bus. In order to prevent two modules transmitting data at once, the processor module 45 controls which module is allowed to transmit. With regards to communication the processor module 45 is seen as the master and the sensor and sample handling modules 47 and 48 are slaves. The software in the microcomputer in each module is programmed with a unique identity, which is made up from a unit type and node number. Having the identity split between unit type and node number allows two modules of the same type to be used in a system each having a different node number. There is also a global indentifier that allows a message from the processor module to be sent to all modules. The processor module polls each of the modules in turn with a message to return their status. Upon receiving the polling message each module returns a message describing the status of the module. This status string of data is unique to the module type. This status string may contain the sensor data, diagnostic info and other status information. The status message also contains the indentifier information. If the processor module 45 does not receive a status return message it knows there is an error with the data link. The processor module 45 may also transmit other commands to various modules, so that the modules can 18 control various functions e.g. change sensor parameters, change physical variables etc.

All messages have information that describes the start and end of the datainformation. There is also error detection information, which provides a means for each module to check that all the data has been correctly received. 5 19

Claims

Claims 1. A chemical sensor system for at or on line monitoring of a

product or process comprising: a sample handling module for acquiring a sample of a substance to be sensed; a sensor module including an array of sensors arranged to sense the sample; and a processing module for deriving information from the output of the sensor module using pattern recognition. 5
2. A system as claimed in claim I wherein the sample handling module acquires a sample using at least one of the following methods portable; liquid headspace; liquid sparge; sample vaporisation; probe; solid headspace; direct insertion of sensor array into sample or sample stream-, gas line; and ambient monitoring. 10
3. A system as claimed in claim I or 2 wherein the sample handling module is arranged to acquire a sample without operator intervention.
4. A system as claimed in claim 1, 2 or 3 wherein the sample handling module is arranged to take a plurality of samples at discrete time intervals.
5. A system as claimed in claim 1, 2 or 3 wherein the sample handling module is arranged to take continuous samples.
6. A system as claimed in any preceding claim wherein the sensor module includes a sensor array using at least one of the following types of sensor technology- mass sensitive sensors; electronic conductance or capacitance sensors; field effect sensors; calorimetric sensors; electrochemical sensors; optochemical or photometric sensors; and biosensors.
7. A system as claimed in claim 6 wherein the sensor array includes sensors of one technology type only.
8. A system as claimed in claim 6 wherein the sensor array includes sensors of a combination of different technology types. 5
9. A system as claimed in any preceding claim wherein the processing module processes data related to a sample or batch of samples to format the data for the application of a pattern recognition technique to it.
10. A system as claimed in any preceding claim wherein the pattern recognition technique uses at least one of the following- a statistical method-, fuzzy logic; an artificial neural network; and a proprietary classifier algorithm.
11. A system as claimed in any preceding claim wherein at least one of the sample handling module, sensor module and processing module incorporates an integral user interface.
12, A system as claimed in any preceding claim and including a user interface module for communicating information to and/or from a user.
13 A system as claimed in claim 12 wherein the output of the processing module is applied to the user interface module.
14. A system as claimed in claim 12 or 13 wherein the user interface module includes means 21 for presenting information to and/or accepting input from, an operator.
15. A system as claimed in claim 12 or 13 wherein the user interface module does not include means for communicating with an operator.
16. A system as claimed in any of claims 12 to 15 wherein the user interface module comprises means for communicating information to and/or from networks external to the chemical sensor system.
17. A system as claimed in any of claims 12 to 16 wherein the user interface module comprises 10 means for providing information for control of a process being monitored.
18. A system as claimed in any of claims 12 to 17 wherein the user interface module includes at least one of the followin& a display; an alarm; a touch-sensitive screen; and digital communication means. 15
19. A system as claimed in any preceding claim wherein the sensor module includes means for acquiring data points to represent signal information and means for transmitting the acquired data points to one or both of the processing module and a user interface module.
20. A system as claimed in any preceding claim wherein data acquisition is carried out by the processing module.
2 1. A system as claimed in any preceding claim wherein the processing module includes 22 means for communicating information to and/or from networks external to the chemical sensor system.
22. A system as claimed in any preceding claim wherein the processing module includes means for providing information for control of a process being monitored.
23. A system as claimed in any preceding claim and including means for providing information from monitored data to control the system itself
24. A system as claimed in any preceding claim and including in-built system diagnostic means for defiving test data or information from a plurality of modules in turn, combinations of modules and/or the entire system.
25. A system as claimed in claim 24 wherein the sample handling module includes means for introducing a calibrant or test sample.
26. A system as claimed in claim 24 or 25 wherein means are included for introducing a calibrant or test sample to the sensor array.
27. A system as claimed in any preceding claim wherein at least one of the sample handling module, sensor module, processing module and a user interface module comprises a plurality of sub-modules.
28. A system as claimed in any preceding claim and including means for communicating with 23 at least one of the modules or between modules via a wireless link.
29. A system as claimed in any preceding claim and including a plurality of at least one of the following types of modules: sample handling module, sensor module-, processing module and user interface module. 5
30. A system as claimed in claim 29 and including a plurality of sample handling modules connected to a common sensor module.
3 1. A system as claimed in claim 29 or 30 and wherein a sample handling module is connected to a plurality of sensor modules.
32. A system as claimed in claim 29, 30 or 31 and including a plurality of sample handling modules each of which is connected to a respective different sensor module.
33. A system as claimed in claim 32 wherein outputs of the sensor modules are connected to a common processing module.
34. A system as claimed in any of claims 29 to 33 and comprising a plurality of user interface modules each being associated with a respective different sensor module. 20
35. A system as claimed in claim 34 wherein the user interface modules include a user display.
36. A system as claimed in claim 34 or 35 wherein each user interface module is connected to 24 both a respective different sensor module and to a common processing module.
37. A system as claimed in claim 29 and comprising a first sample handling module, sensor module, and processing module and a second sample handling module, sensor module, and processing module, the first modules and the second modules being located at first and second respective different locations.
38. A system as claimed in claim 37 and including a first user interface module at the first location and a second user interface module at the second location.
39. A system as claimed in claim 37 and including a user interface module remote from the first and second locations and connected to at least one of the first modules and to at least one of the second modules.
40. A system as claimed in any of claims I to 3 5 wherein at least one of a sensor module, processing module and a user interface module are located locally to the or a sample handling module.
4 1. A system as claimed in any claims I to 3 5 wherein the a user interface module is located remotely ftom the sample handling module.
42. A system as claimed in any of claims I to 3 5 wherein a user interface module and the processing module are located remotely from the sample handling module.
43. A system as claimed in any of claims I to 35 wherein the processing module is located remotely from the sample handling module, and the sensor module and a user interface module are local to the sample handling module.
44. A system as claimed in any preceding claim wherein the processor module controls communication with other modules.
45. A system as claimed in any preceding claim wherein at least some of the modules include an identifier including a unit type and node number.
46. A system as claimed in any preceding claim and including means for the processor module to communicate with a plurality of modules simultaneously.
47. A system as claimed in any preceding claim wherein the processor module polls other modules in turn for their status information. 15
48. A system as claimed in claim 47 wherein the status information includes identifier information, sensor data and/or diagnostic information.
49. A system as claimed in claim 47 or 48 wherein each message communicated between 20 modules includes start and end of data information.
50. A system as claimed in any preceding claim and including means for detecting errors in data transmitted between modules.

26
5 1. A system as claimed in any preceding claim for monitoring at least one of the following products and processes water industry, fermentation, food and beverages, quality/status of intermediate products, petrochemicals, medical, hygiene, microbial, security, transport, and household and personal care.
52. A chemical sensor system substantially as illustrated in and described with reference to one or more of the accompanying drawings.