GB2323672A

GB2323672A - Distributed measuring heads for gas-measuring apparatus

Info

Publication number: GB2323672A
Application number: GB9806671A
Authority: GB
Inventors: Herbert Kiesele; Uwe Kuehn; Frank Mett
Original assignee: Draegerwerk AG and Co KGaA
Current assignee: Draegerwerk AG and Co KGaA
Priority date: 1997-03-29
Filing date: 1998-03-27
Publication date: 1998-09-30
Anticipated expiration: 2018-03-27
Also published as: GB2323672B; GB9806671D0; DE19713367C1

Abstract

One or more gas sensors can be connected 4 to each measuring head 2 and the heads are designed to communicate bidirectionally with a central evaluating unit by a wireless link. Each head is provided with a transmitting and receiving device for wireless communication with the evaluating unit, and is provided with a battery so that it has an independent source of power, simplifying positioning of the measuring head since lead connections to the central unit are not required. The battery may be charged by solar cells 3 which can be on detachable leads for locating at a suitable location near to the measuring head. The measuring head preferably comprises a processor, display 6 and an internal processor with controls 5 for evaluating signals from the sensor(s). The gas sensors preferably have built-in memory in which sensor specific data such as gas detected, measurement ranges and calibration data is permanently programmed.

Description

2323672 Measurinq head for a qasmeasurinq apparatus havinq distributed

measurinq heads The invention relates to a measuring head for a gas-measuring apparatus having a plurality of distributed measuring heads.

Such measuring heads and gas-measuring apparatus are used in the chemical industry, laboratories, gasoperated systems, oil-drilling stations etc. as monitoring or alarm devices. A gas-measuring apparatus of the kind mentioned is known, for example, from DE 38 19 128 C2. The gas-measuring apparatus has a plurality of measuring heads which can be set up in distributed positions in the area to be monitored and which are connected to a central evaluating unit by way of electric leads. The leads connecting the measuring heads to the central evaluating unit are twowire leads. The apparatus is designed so that, on the one hand, bidirectional, digital communication can be carried out by way of the two-wire leads in accordance with a known multi- party process in order to permit data exchange between the evaluating unit and the measuring heads and so that, on the other hand, the supply of power to the measuring heads is also effected by way of the two-wire leads. Although only one twowire lead is therefore required for the purpose of connecting each measuring head to the central evaluating unit, the installation outlay for such a gas-measuring apparatus is still considerable, in particular if a large number of measuring heads is to be installed at scattered locations over a large monitoring area and connected with leads. This comparatively high installation outlay is particularly disadvantageous if it is desired to be able to switch or move individual measuring heads in a simple manner.

Embodiments of the present invention provide an improved measuring head for a gas-measuring apparatus of the kind mentioned above so that the gas-measuring apparatus can be installed simply and the measuring head can be moved with reduced outlay in terms of 5 assembly.

According to the invention, there is provided a measuring head for a gasmeasuring apparatus having a plurality of distributed measuring heads in bidirectional communication with a central evaluation unit, to which measuring head one or more gas sensors can be connected, wherein the measuring head is equipped with a transmitting and receiving device for wireless communication with a corresponding transmitting and receiving device in the evaluation unit and is provided with a source of electric power for the measuring head. The measuring head is thus a selfsufficient unit which can communicate with the central evaluating unit without lead connections and is supplied with electricity from the source, which may be a battery.

As a result of this configuration, the assembly outlay is minimized, since the individual measuring heads can be simply set up in the desired positions without any cabling being required. The movement of individual measuring heads is accordingly possible with minimal outlay.

The battery is preferably a rechargeable battery. The battery for the power supply can be designed to guarantee a sufficiently long period of operation of the measuring head before it needs to be exchanged or re-charged.

In an advantageous embodiment, each measuring head is provided with solar cells and a charging circuit arrangement for charging the battery, the charging circuit being fed by the solar cell voltage when the solar cells supply sufficient voltage. In this embodiment, it is possible to extend, to a substantial extent, the intervals between servicing when the battery of the measuring heads would otherwise need to be exchanged or re-charged, and in favourable situations to dispense entirely with an exchange or external re-charging of the battery, if it is possible to bring the solar cells on the measuring head into an at least temporarily illuminated area at the desired measuring station.

The measuring head can be made more flexible by allowing the solar cells to be removed from the measuring head by electrically connecting them to the measuring head by means of connecting cables so that they can be installed away from the measuring head in an area with more favourable lighting conditions.

The measuring head is preferably provided with a processor unit for processing the signals supplied by the sensor or the sensors, and for controlling the transmitting and receiving device for the transmission of the sensor data to the evaluating unit. Processing of the sensor signals in the processor unit can include calibration and, if applicable, conversion of the signals into the desired measured values. As a result, it is possible to provide on the measuring head a display unit on which the signals supplied by the sensor or the sensors can be displayed in a form in which they have already been converted into the desired measured values.

The transmitting and receiving devices can be known radio devices to which control circuit arrangements are connected in order to render possible bidirectional communication according to a multi-party process between the measuring heads and the central evaluating unit. Such bidirectional communication processes and radio devices are known per se and will not be discussed in greater detail in the following.

A specific embodiment of the invention will now be described, purely by way of example, with reference to the accompanying drawing which shows a single measuring head for a gas measuring apparatus.

The measuring head 1 has a housing 2 with a connection 4 for the attachment of a gas sensor (not shown). The gas sensor supplies electrical measurement signals which are routed via the connection 4 to a processor unit in the measuring head 1. The gas sensor can, for example, be an electrochemical or even an optical gas sensor. The processor unit calibrates and evaluates of the measurement signals of the gas sensor so that the desired measured variable is available locally at the measuring head 1. The converted measured value can then already be displayed on a display 6 on the measuring head 1.

A source of electric power, here an accumulator (rechargeable battery) is provided.

The gas sensor signals, which are processed in the processor unit, are routed via a transmitting and receiving device in the measuring head 1 to a central evaluation unit (not shown) by radio transmission of the desired data. The communication is thus carried out without leads. The central evaluation unit with its transmitting and receiving device can in turn activate the individual measuring heads and can transmit data and commands to the processor units in order to effect certain calibrations or carry out tests at the individual gas sensors.

The individual gas sensors are advantageously 3 )0 provided with a built-in memory in which sensorspecific data is permanently programmed. Such data can, for example, include the type of gas detected by the gas sensor, measurement ranges, calibration constants or calibration curves, etc. This enables gas sensors on a measuring head 1 to be exchanged, and the processor unit in the measuring head 1, with the aid of the sensor-specific data received from the memory of the gas sensor, can carry out local processing of the gas sensor signals and display the result even when an alternative gas sensor is attached. Furthermore, the sensor-specific data is also used to route the information relating to the specific gas sensor to the evaluation unit.

on the housing 2 of the measuring head 1 control knobs 5 are provided which allow inputs to be entered into the processor unit of the measuring head 1 in situ in order to be able to control the unit's operating mode, the display mode on the display 6 and the like.

An alarm device may be provided, which triggers an alarm when the processor detects predetermined gas sensor signals. The alarm device preferably emits an audible alarm.

The measuring head 1, which is shown in Figure 1, forms a completely selfsufficient unit which can be set up or fitted at a desired measuring station without any further installation work. Even once the gasmeasuring apparatus has been installed, the apparatus can be rearranged in a very simple and flexible manner if it is desired that individual measuring heads or all the measuring heads are set up at new measuring stations. No cabling connecting the measuring heads with each other or for the purposes of connection to the central evaluating unit is required at all for the installation or for the re-positioning of the measuring heads.

The solar cells 3 can be fixedly connected to the housing 2 of the measuring head 1, as shown in Figure 1. Alternatively, the solar cells can also be in the form of a unit which is detachable from the housing 2, this making it possible to bring the solar cells into better illuminated position close to and spaced away from certain measuring stations if the lighting conditions are unfavourable at the location of the measuring station itself. Such a detachable solar cell unit is then connected to the charging circuit arrangement and the accumulator in the measuring head 1 by means of a simple cable connection, i.e. by one or more leads-

Claims

1. A measuring head for a gas measuring apparatus having a plurality of distributed measuring heads in bidirectional communication with a central evaluation unit, to which measuring head one or more gas sensors can be connected, wherein the measuring head comprises a transmitting and receiving device for wireless communication with a corresponding transmitting and receiving device in the evaluation unit and a source of electric power for the measuring head.

2. A measuring head according to claim 1 in which the source of electric power is a rechargeable battery.

3. A measuring head according to claim 2, wherein the measuring head is provided with solar cells which feed a circuit arrangement for charging the rechargeable battery.

4. A measuring head according to claim 3, characterised in that the solar cells can be removed from the measuring head and are electrically connected to the measuring head by way of leads, so that they can be installed spaced away from the measuring head.

5. A measuring head according to claim 3 having a housing containing the transmitting and receiving device and battery, to which housing the solar cells are fixedly attached.

6. A measuring head according to any preceding claim, wherein the transmitting and receiving device in the measuring head is a radio device suitable for bidirectional communication according to a multi-party process.

7. A measuring head according to any preceding claim, wherein the measuring head is provided with a processor unit for processing the signals, which are supplied by the sensor or the sensors, and for controlling the transmitting and receiving device for the transmission of sensor data to the evaluation unit and for receiving data from the evaluation unit. 5

8. A measuring head according to claim 7, further comprising a display wherein the processor unit is adapted to display the processed gas sensor signals as measured values on the display.

9. A measuring head according to claim 7 or 8, further comprising an alarm device and wherein the processor unit is adapted to trigger the alarm device under given conditions in response to the processed gas sensor signals.

10. A measuring head according to any preceding claim, further comprising a memory associated with each gas sensor in which memory sensor-specific data is permanently programmed.

11. A gas-measuring apparatus having at least one separate measuring head according to any preceding claim and a central evaluation unit which has a transmitting and receiving device for bidirectional wireless communication with the transmitting and receiving device in the measuring head.

12. A measuring head substantially as herein described with reference to and as shown in the accompanying drawing.

13. A gas-measuring apparatus substantially as herein described with reference to the accompanying drawing.