WO2002073161A1

WO2002073161A1 - Gas sampler

Info

Publication number: WO2002073161A1
Application number: PCT/GB2002/001076
Authority: WO
Inventors: Daniel White; Thomas Stephen Lamb
Original assignee: The Secretary Of State For Defence
Priority date: 2001-03-13
Filing date: 2002-03-08
Publication date: 2002-09-19
Also published as: GB0106087D0

Abstract

A gas sampler comprising a control means (1), at least one valve (3), a pump means (5) and at least one flow connection means (10), each valve (3) being in fluidic communication with a flow connection means (10), and each flow connection means (10) being connectable to a sample collection means (7) wherein, in use, the control means (1) controls the operation of the at least one valve (3) such that the pump means (5) causes flow of gas into the sample collection means (7) wherein the gas sampler further comprises a least one flow sensor (4) and a recording means (2) for the recording of the rate of gas flow through the gas sampler as a function of time.

Description

Gas sampler

The invention in suit relates to the field of fluid sampling and samplers, more particularly but not exclusively to the field of gas sampling and gas samplers. Gas sampling is intended to include the collection of gas and the collection of gas-borne samples, such as vapours and particulate. It is anticipated that air sampling will be the most common field of use of the present invention.

Gas sampling has been performed for many years by those wishing to monitor the concentration of gas-borne material, such as particulate (e.g. smoke) and chemicals present as vapours. It is anticipated that the demand for gas samplers will increase, given the proliferation in environmental regulation in the recent past and that which can be anticipated in the near future.

For many years, gas sampling in the military field has used a simple, bulky sampler. This sampler typically comprises a pump, an air inlet, several sample collection means and a valve. The pump draws air through the sampler air inlet to the selected sample collection means, through the valve and out of an exhaust. The application of an electrical pulse by a suitable control system causes the valve outlet port to rotate, thus guiding air to the next sample collection means. The system is large and bulky and requires mains power operation. The flow rate cannot be altered and hence inappropriate flow rates are often used for the sample collection means in question. Furthermore, sampling is only possible in sequence, since the valve outlet port is caused to rotate in one direction only to the next sample collection means. The capability of the system is largely dependent on the integrity of the valve. The valve comprises two steel plates which need to be machined to extremely tight tolerances, thus making the sampler very expensive. Furthermore, the plates often becomes blocked in use by particulate or chemical challenge, thus causing the failure of the whole sampler.

Some of the failures of the above-mentioned sampler are addressed by the FLEC Air Pump 1001 gas sampler (CHEMATIC, Denmark). This battery-powered sampler comprises a pump, a flow sensor, an air inlet, a valve, a flow display means and a single sample collection means. The flow rate is variable and can be set via a personal computer. The sampler will try to maintain a constant flow-rate when operating by altering the output of the pump. However, this sampler is expensive, services only one sample collection means, does not record the gas flow as a function of time and does not permit two-way communication with an external control source or data collection means. The last two omissions prevent the user from calculating the concentration of gases collected by the sampler.

EP0129113 describes a gas sampling apparatus for the collection of ^l4C in carbon dioxide, the sampler comprising a pump, gas inlet, two sample collection means, a pressure sensor, a means of maintaining a constant pressure and valves to facilitate control of the airflow into the sampler. This sampler only allows sampling from one place and use of one sample line to feed two sample collection vessels could potentially cause cross-contamination of samples. Furthermore, the volume of sampled gas is not known and hence concentration analysis cannot be performed.

SU1067392 discloses a gas sampling apparatus for remote collection of samples from dangerous environments. Many sampling lines are used to supply one sample collection means, thus creating the possibility of cross-contamination between samples taken at different times. Furthermore, the volume of sampled gas is not known and hence concentration analysis cannot be performed.

The invention in suit overcomes some of the problems of the prior art and provides a relatively inexpensive, reliable and easily reconfigurable gas sampler.

According to the present invention, a gas sampler comprising a control means, at least one valve, a pump means and at least one flow connection means, each valve being in fluidic communication with a flow connection means and each flow connection means being connectable to a sample collection means wherein, in use, the control means controls the operation of the at least one valve such that the pump means causes flow of gas into the sample collection means wherein the gas sampler further comprises a least one flow sensor and a recording means for the recording of the rate of gas flow through the gas sampler as a function of time. This provides a sampler that is capable of recording gas flow through the sensor. Those skilled in the art will realise that the sample collection means is not necessarily part of the gas sampler.

The gas sampler preferably comprises a plurality of valves, each valve being individually associated with a flow connection means. Thus, each valve and flow connection means form a sample collection line that can be connected to a sample collection means.

It is preferred that the control means is further in communication with the at least one flow sensor and optionally the pump means such that, in use, a substantially constant flow of gas may be maintained through the gas sampler. The substantially constant gas flow rate may advantageously be varied from one gas collection process to the next. This allows the flow rate to be optimised for the particular type of collection means that is used. The collection means may be a bubbler tube, tubes containing an adsorbent material such as Tenox or a particulate trap, such as an impinger. Those skilled in the art will be aware of many other types of collection means too numerous to mention.

The recording means may be located locally with, or remote from, the sampler. The record of the flow rate will enable the user to calculate the concentration of the material of interest. The recording means may be in communication with either the flow sensor itself or with the control means.

The sampler may optionally further comprise data input means, said data input means being in communication with the control means so as be able to transmit data to the control means. The data input means may comprise a microprocessor, and may be a personal computer. The data input means may comprise a wireless receiver or transceiver to permit remote control of the sampler. The data transmitted to the control means may typically include the times for collection of gas, the identity of the collection means and the duration of the gas collection for the given collection means. The sampler may also be used to sample a set volume of gas.

The sampler may comprise data output means for transmitting data from the gas sampler, said data output means being in communication with the recording means so as to be able to receive data transmitted from the recording means. Alternatively, the data output means is in communication with either the control means or the at least one flow sensor so as to be able to receive data transmitted from either the control means or the at least one flow sensor. The output means can then transmit the said data to a remote user or operator using any known data transmission hardware, such as a wireless transmitter or transceiver. The data output means may be the data input means.

The gas sampler may comprise a communications output means for enabling the sampler to transmit control information to another sampler and a communications input means for enabling the sampler to receive control information from another sampler. The communications output means may be the data output means. The communications input means may be the data input means.

The gas sampler preferably further comprises a battery power source. This allows the unit to be portable. The control means may be designed to allow the sampler to operate on a "standby" mode until the sampler is to be used, so that batteries are not run-down unnecessarily.

The gas sampler may comprise at least one sample collection means.

A second embodiment of the invention provides a gas sampling array comprising a plurality of gas samplers in accordance with the present invention.

The gas sampling array may comprise a plurality of gas samplers according to the present invention, wherein the communications output means of a first gas sampler is in communication with the communications input means of each of the other gas samplers such that the operation of the other samplers is controlled by the first gas sampler. In this case, the first sampler acts as a master, whilst the others act as slaves. One can program the one sampler to control the activities of all of the other samplers. Furthermore, if one of the samplers fails (save for the first sampler), then the rest of the samplers will continue to sample.

Alternatively, the gas sampling array comprises a plurality, y, of gas samplers according to the present invention, wherein the communications input means of the n^th gas sampler is in communication with the communication output means of the (n-l)^th gas sampler, and wherein the communication output means of the n^th gas sampler is in communication with the data input of the (n+l) ^h gas sampler, n being in the range 1 to y-1, the data input means of the first gas sampler being connected, in use, to an external data supply source. This series arrangement of samplers allows a 'string' of samplers to be addressed by one master sampler, with the master sampler only requiring a single standard output communications port.

Alternatively, the gas sampling array comprises a plurality, y, of gas samplers according to the present invention, wherein the communications input means of the n^th gas sampler is in communication with the communications output means of the (n-l)^th gas sampler, and wherein the communications output means of the n^th gas sampler is in communication with the communication input means of the (n+l)^th gas sampler, n being in the range 1 to y-1, the communications input means of the first gas sampler being in communication with the communications output means of the y' sampler. This provides a ring array wherein the control information may be transferred back to the controlling first sampler.

In the case of a gas sampling ring array comprising two samplers, the communications output means of the first gas sampler is in communication with the communications input means of the second gas sampler and the communications output means of the second gas sampler is in communication with the communications input means of the first gas sampler.

A third embodiment of the invention provides a method of sampling gas the method comprising using a gas sampler in accordance with the present invention.

A fourth embodiment of the invention provides a method of sampling gas the method comprising using a gas sampling array in accordance with the present invention.

The invention in suit will now be described by way of example only with reference to the following figures of which:

Figure 1 is a schematic representation of a gas sampler in accordance with the present invention;

Figure 2 is a representation of a sampler in accordance with the present invention; Figure 3 is a schematic representation of an array of gas samplers in accordance with the present invention; and Figure 4 is a schematic representation of an alternative array of gas samplers in accordance with the present invention.

Figure 1 shows a schematic representation of a gas sampler in accordance with the present invention. The sampler comprises a control means 1, a recording means 2, valves 3a-3e, a flow sensor 4, a pump 5, an input means 6, flow connection means 10a- lOe, data output means 8, manifold 11, gas exhaust 12 and battery power supply (not shown). Those skilled in the art will realise that the sample collection means 7a-7e are not an essential part of the invention; they may be supplied separately from the rest of the sampler.

The control means 1 in this example comprises a microprocessor with RAM, ROM and suitable electrical input and output ports to enable communication with the valves 3a-3e, the flow sensor 4, pump 5, input means 6, recording means 2 and output means 8. The valves 3a- 3e are solenoid valves that are easily activated using low voltage electrical signals. The flow sensor 4 is a mass airflow sensor that generates a current proportional to the gas flow through the sensor 4. The pump 5 is a small battery powered electrical pump. The input means 6 comprises a hand-held unit comprising a microprocessor and a keypad. Each of the sample collection means 7a-7e is in gaseous connection with a corresponding valve 3a-3e by virtue of a flow connection means. Each of the sample collection means 7a-7e comprises one of a variety of sample receptacles such as particulate capture vessels or 'bubblers' (a term of the art). Each of the sample collection means 7a-7e is located so as to enable gas to be collected from a desired location. Thus gas collected from a particular location is channelled through a sample collection means 7a-7e, through the corresponding flow connection means 10a- lOe, through the corresponding valve 3a-3e, through the manifold 11, through the flow sensor 4, through the pump 5 and out of the exhaust 12. Material within the sampled gas is retained within the sample collection means 7a-7e. Input data is programmed into the input means 6 via the key pad by a user. This is transferred from the input means 6 to the control means 1 via, for example, a known communication cable. At the appropriate time determined by the input data, electrical signals are generated by the control means 1 and transmitted to one of the valves 3a-3e to open the selected valve, 3a say. At approximately the same time, the control means 1 transmits signals to the pump 5 which cause the pump 5 to draw air through the relevant air inlet 10a through the open valve 3 a into the sample collection means 7a. The said signals to the pump 5 will determine the gas flow rate. As mentioned previously, the flow sensor 4 is situated between the valves 3a-3e and the pump 5 such that gas drawn through the relevant valve, 3a, say passes through the sensor 4, said sensor 4 measuring the gas flow in the sampler. This embodiment permits the use of only one sensor. In this preferred embodiment, the sensor 4 transmits the flow information to the control means 1 ; if the flow rate is too low, then the control means 1 causes the pump 5 to try to increase the flow rate and conversely if the flow rate is too high, then the control means 1 causes the pump 5 to try to decrease the flow rate. Thus, the pump 5, control means 1 and flow sensor 4 operate is a closed feedback loop configuration. It is quite possible for the invention in suit to operate without maintaining a constant flow rate; the flow sensor 4 may be used merely to determine the gas flow.

In this example, the flow information transmitted to the control means 1 by the flow sensor 4 can either be transmitted to the recording means 2 for storage (usually as a function of time) or transmitted to a remote means for displaying or recording the data. The recording means 2 provides a means of storing sampling information. From such information, sample concentrations can be calculated. In this example, the recording means is an EPROM, so that if the battery power supply fails, then the data stored within the recording means 2 is not deleted.

In this example, the control means 1 will eventually close the open valve 3a in accordance with its programming. The gas flow rate will always be monitored by the flow sensor 4. Another of the valves 3b-3e is then opened at a time determined by the programming of the control means 1. It is possible to open more than one valve at once, although this is not usually desirable. It is, of course, possible to use more than one flow sensor 4 to enable the monitoring of multiple flow sensors 4 to allow for simultaneous monitored collection of samples using more the one sample collection means 7a-7e at any one time.

After the gas collection cycle is complete, the sample collection means 7a-7e may be disconnected from the sampler and the contents analysed. The gas flow data from the recording means 2 are either obtained remotely or locally via the data output means 8. The data output means 8 may, for example, comprise a communications port, a microprocessor and suitable cabling or remote link (such as a radio transmitter). From the sampler program it is known when each of the valves 3a-3e is open. The gas flow rate is known as a function of time from the data stored within the recording means 2 or transmitted to a remote means of recording via the data output means 8. Hence, it is possible to determine the total gas flow through each of the valves 3a-3e. The contents of each sample collection means 7a-7e can be analysed and quantified, and thus one can calculate the effective gaseous concentration of analyte from the volume of gas that has flowed through the sample collection means 7a-7e and the amount of analyte found therein. Such concentration data can be invaluable in the monitoring of pollution. The monitoring of the flow rate is vital to the obtaining of this data.

Figure 2 shows a representation of a sampler in accordance with the present invention, the sampler comprising control means 101, recording means 102, twelve valves 103, flow sensor 104, pump 105, input means 106, data output means 108 comprising a microprocessor 108a and electric cable and interface socket 108b, manifold 111, flow connection means (not shown), visual display 113, battery (not shown) and enclosure 120 comprising body portion 114 and lid portion 115. The body portion 114 is provided with a raised lip 116 that engages with the silicone seal 117 provided on lid portion 115 when the body 114 and lid 115 portions are brought together to form a closed enclosure 120. The engagement between the raised lip 116 and silicone seal 117 ensures that the components within the enclosure 120 are suitably protected from the outside environment. Body portion 114 and lid portion 115 are held together by screws (not shown). The enclosure 120 provides electromagnetic shielding for the components within.

The sampler is optimised for low power operation. The valves 103 are low power miniature solenoid valves. The visual display 113 is a low power liquid crystal display that is timed so as to avoid unnecessary illumination. Pump 105 is a low power rotary vane pump. The battery is a rechargeable nickel metal hydride (NiMH) battery, with the sampler being provided with suitable circuitry for charging the battery. A battery condition indicator is provided on the visual display 113. As an alternative to battery power, the sampler may be powered from a 12 N DC (max 300mA) supply.

A flow connection means is provided for each valve 103. The twelve flow connection means are located on the unseen side of the lid portion 115. Those skilled in the art will realise that the number of flow connection means is limited by the desired size of the sampler. The number of sample collection means is ultimately only limited by the processing power of the control means 101.

The sampler operates essentially as described above with reference to figure 1. With reference to figure 2, the control means 101 causes one of the valves 103 to open so that the action of the pump 105 causes air to be drawn through the flow connection means corresponding to the opened valve 103, through the valve 103, through the manifold 111, into the flow meter 104, into the pump 105 and out of the exhaust 112. One valve 103 may be open at any time.

The flow sensor 104 comprises a miniature solid-state mass airflow sensor, giving the sampler a flow operating range of 0-1000 ml/min. Selection of a different flow sensor 104 and pump 105 will give a different operational flow range. Flow sensor data are translated by a 12 bit A-to-D convertor and are logged by recording means 102. Recording means 102 comprises a non- volatile logging memory capable of recording more than 15000 time-and- day stamped flow readings. The time-and-day information is provided by a battery-backed real time clock. Recording means 102 also records sample number (i.e. which of the sample collection means is being used) and operating mode of the sampler (e.g. such as whether the sampler is a "slave" or "master" unit). Data input means 106 comprises a four button array said buttons being of such size and mutual spacing so as to be operable by a user wearing protective heavy-duty gloves. The four button array drives a menu system, the menus being displayed on the visual display 113. The four button array, in conjunction with the visual display, may be used to program the sampler. Alternatively, the sampler may be programmed via a suitable interface (not shown), in this case RS232, from a personal computer or other device capable of downloading data. Control means 101 is provided with the software necessary to facilitate the input of program data and output of sampling data as described above.

The sampler may be calibrated by comparing the flow rate readings generated by the flow sensor 4 and a suitable standard flow meter (not shown) attached to the sampler. The sampler is provided with communications input and output means (not shown). This allows samplers to operate in an array. For example, one sampler may act as master, whereas the other samplers would be slave units under the control of the master.

Those skilled in the art will realise that input means and data output means other than those given in the examples are suitable for incorporation into the invention in suit. Valves other than the solenoid-type valves can be used. Many different types of collection means can also be used. Furthermore, the gas sampler may be powered by electrical means other than batteries, such as mains electricity or via solar cells. One valve may also be used for many collection means. Many types of pumps may be used and these will be obvious to those skilled in the art. Similarly, many types of flow meter may be used. The sampler may comprise a communications output means which can be used to transmit information to other samplers. This may comprise a standard communications port (e.g. IEEE, RS-232). The communication output means may be the data output means. The communications input means may also be the data input means e.g. both use an RS-232 interface. The communication output means will usually be in communication with the control means.

The samplers in accordance with the present invention may be linked together to form arrays. A first example of an array is shown in figure 3, said array comprising 6 gas samplers 20, 21, 22, 23, 24, 25, the sampler 20 comprising a communications output means (not shown) in communication with the communication input means of each of the other samplers 21-25 such that the operation of samplers 21-25 is controlled by sampler 20. The communication may be achieved, for example, by wired or preferably wireless telecommunications. In this configuration, the sampler 20 acts as a master unit, receiving the sampling information for all of the samplers 20-25 via its communication input means (not shown). In one embodiment, each sampler 20-25 may record information locally and transmit it directly back to the user via each data output means (not shown). Alternatively, each of the samplers 21-25 may transmit sampling information to sampler 20, which then stores and transmits information to the user. This array configuration offers many advantages. It allows many samplers to be controlled by one master unit and, furthermore, if one of the samplers 21-25 fails, then only the said sampler fails. A second example of an array in accordance with the present invention is shown in figure 4. The array comprises 6 samplers, 30-35, the communications output means of 30 (not shown) being in communication with the communications input means of sampler 31, the communications output means of sampler 31 being in communication with the communication input means of sampler 32 and so on. The communication output means of sampler 35 is in communication with the communication input means of sampler 30, thus forming a ring network topology. This configuration allows sampler 30, the master, to be programmed and to control the activity of all of the other controllers 31-35, the slave. This configuration also allows the communications output means of 30 to comprise a standard port that only needs to be able to connect to one communication input means. Each slave functions as a transceiver. The master compares the returned information that has traversed the loop with the sent information so that the master may make the appropriate error detection and correction decisions. Each of the samplers 30-35 has recording means (not shown) on which to record air flow versus time data. The data may then be transmitted via a data output means (not shown) of each sampler 30-35 to an external collecting point, or may be transmitted via the array of samplers to sampler 30 for transmission to an external collecting point. Alternatively, the samplers 31-35 may not record information, but transmit it as it is recorded, either to the master sampler 30 or to an external collecting point.

The sampler has been described as a gas sampler. Those skilled in the art will realise that, with suitable non-inventive modifications, the sampler could be used to collect fluids other than gases, such as liquids.

Claims

1. A gas sampler comprising a control means, at least one valve, a pump means and at least one flow connection means, each valve being in fluidic communication with a flow connection means, and each flow connection means being connectable to a sample collection means wherein, in use, the control means controls the operation of the at least one valve such that the pump means causes flow of gas into the sample collection means wherein the gas sampler further comprises a least one flow sensor and a recording means for the recording of the rate of gas flow through the gas sampler as a function of time.

2. A gas sampler according to claim 1 wherein the control means is further in communication with the at least one flow sensor and optionally the pump means such that, in use, a substantially constant flow of gas may be maintained through the gas sampler.

3. A gas sampler according to either claim 1 or claim 2 comprising a plurality of valves, each valve being individually associated with a flow connection means.

4. A gas sampler according to any one preceding claim further comprising data input means, said data input means being in communication with the control means so as be able to transmit data to the control means.

5. A gas sampler according to any one preceding claim comprising data output means for transmitting data from the gas sampler, said data output means being in communication with the recording means so as to be able to receive data transmitted from the recording means.

6. A gas sampler according to any one of claims 1 to 4 comprising data output means for transmitting data from the gas sampler, said data output means being in communication with either the control means or the at least one flow sensor so as to be able to receive data transmitted from either the control means or the at least one flow sensor.

7. A gas sampler according to either of claims 5 and 6 wherein the data output means is the data input means.

8. A gas sampler according to any one preceding claim comprising a communications output means for enabling the sampler to transmit control information to another sampler and a communications input means for enabling the sampler to receive control information from another sampler.

9. A gas sampler according to claim 8 wherein the communications output means is the data output means.

10. A gas sampler according to any one preceding claim further comprising at least one sample collection means.

11. A gas sampling array comprising a plurality of gas samplers in accordance with any preceding claim.

12. A gas sampling array comprising a plurality of gas samplers according to either of claims 8 and 9, wherein the communications output means of a first gas sampler is in communication with the communications input means of each of the other gas samplers such that the operation of the other samplers is controlled by the first gas sampler.

13. A gas sampling array comprising a plurality, y, of gas samplers according to any one of claims 8 and 9, wherein the communications input means of the n gas sampler is in communication with the communications output means of the (n-l)^th gas sampler, and wherein the communications output means of the n^th gas sampler is in communication with the communication input means of the (n+l)^th gas sampler, n being in the range 1 to y-1, the communications input means of the first gas sampler being in communication with the communications output means of the y^th sampler.

14. A gas sampler substantially as hereinbefore described with reference to figures 1 and 2.

15. A gas sampling array substantially as hereinbefore described with reference to figure 3.

16. A gas sampling array substantially as hereinbefore described with reference to figure 4.