Title of Invention

A DATA ACQUISITION SYSTEM USEFUL FOR UNDERGROUND MIHES

Abstract

A data acquisition system useful for underground mines which comprises one or more underground data stations (l)(fig.l), the said data station consists of appropriate sensor (4)(fig.3), output of the said data station being connected to the input of a signal processor (5)(fig.3), the said signal , processor (5) being connected to an analog to digital converter (8)(fig.3) of an underground microprocessor board (6)(fig.3) through a data link (2)(fig.3), serial port (9)(fig.3) of the said underground microprocessor board being connected to a surface microprocessor (10)(fig.4) of surface data station (3)(fig.l), the said surface microprocessors being connected to a personal computer (ll)(fig.4), the said sensors, signal processor, underground and surface microprocessors and the personal computer all being connected to an stablised intrinsically safe power supply (7)(fig.7).

Full Text

This invention relates to a data acquisition system useful for underground mines. This invention particularly relates to a microprocessor based intrinsically safe data acquisition system. In underground mines electrical signals equivalent to measured values of various parameters such as methane, carbon monoxide, air velocity, temperature, pressure etc. are transmitted from various areas in the underground mines to a central place at surface. In presently known data acquisition systems, a same or different pair of telephone cable is used for transmission of data from different areas in mine. The system generally consists of data stations underground, linked with a central console at surface with single/different pair of cables. Power supply for underground units is generally taken from underground power source using flame proof (FLP) structure and a chargeable battery is kept as an alternative source of power. In some cases charging of the battery is used which is either charged from surface through same pair of cable or periodically brought to surface for charging. These above described systems have the drawbacks such as: (i) use of FLP structure in underground areas is generally not preferred if intrinsically safe (I.S) circuit can be designed; (ii) placement of local batteries underground creates maintenance problem; (iii)charging from surface requires additional pair of cables which increases cost of cable; (iv) these arrangements require more electronic equipment at underground which is generally not preferred from maintenance point of view. The object of the present invention is to provide data acquisition system useful for underground mines which obviates the above noted drawbacks. We have found by our research and development efforts that: (i)by using microprocessor based switching, it is Possible to share intrinsically safe (I.S. ) power from surface to underground units and data from underground units to surface, on the same pair of cable, thereby reducing cost of cable. (ii) It is further possible to share power for methane sensor, power for underground data station and data from underground to surface on time division multiplexing (TDM) mode. (iii)Using a microprocessor based underground data station it is possible to simplify electronic circuitry for ease of maintenance. (iv)Any form of modem acoustical or optical could be avoided for data transmission up to 4 kilometers between underground data station and central console using input/output port (RS232C/RS422). Accordingly, the present invention provides the data acquisition system useful for underground mines which comprises one or more underground data stations (1)( fig.l), the said data station consists of appropriate sensor (4)(fig.3), output of the said data station being connected to the input of a signal processor (5)(fig.3), the said signal processor (5) being connected to an analog to digital converter (8)(fig.3) of an underground microprocessor board (6)(fig.3) through a data link (2)(fig.3), serial port (9)(fig.3) of the said underground microprocessor board being connected to a surface microprocessor 10)(fig.4) of surface data station (3)(fig.l), the said surface microprocessors being connected to a personal computer (1 l)(flg.4), the said sensors, signal processor, underground and surface microprocessors and the personal computer all being connected to an stablised intrinsically safe power supply (7)(fig.7). The system will now be described with the help of diagrams of the drawings accompanying this specification. The data acquisition system according to the present invention consists of the following features as shown in the figure 1 and to 9 I underground data station, its number depending upon the number of districts (locations) II Data link III Surface data station. In the drawings figure 1: represents block diagram of the system with separate data 1 links (2) interconnecting underground data station (i) with surface computer. figure 2: represents block diagram of the system with common data link(2) interconnecting all underground data stations (i) with surface computer (11). Figure 3 represents the block diagram of the underground data station (1). Figure 4 represents the block diagram of the surface microprocessor boards (10) along with the computer (11) . Figure 5 represents the schematic diagram of interconnection of surface micropro-cessors (10) and their connection the transmitting (14), ground (15) and receiving (16) wires of the data link (2). Figure 6 represents the circuit diagram of the intrinsically safe power supply (12) system. Figure 7 represents microprocessor based switching of power and data. Figure 8 represents sharing of power and data on same cable using time division multiplexing for single data station. Figure 9 represents sharing of power and data on same cable using time division multiplexing by different data stations. (i) Underground data station: - A number of data stations (1) are connected with separate cable (2) as shown in figure 1 or share the same common bus as shown in figure 2. An underground data station as shown in figure 3, comprises of different sensors (4), signal processors (5), microprocessor board (6) and an intrinsically safe stablised power Supply (7) with switching arrangement. An intrinsically safe power is fed from surface to under ground data station. The intrinsically safe power supply itself is powered by an uninterruptible power supply at surface Sensors: The output of all sensors (4) such as methane, carbon monoxide, air velocity, pressure, temperature has to be maintained between 0 to +5 volt for full scale deflection of parameters in question. Signal processor: The signal processor (5) is based on operational amplifier such as IC 741 op-Amp which is commercially available. The input signal from each sensor is in millivolts and is fed to the signal processor. The signal processor amplifies the signal to give it in the range of 0-5 volts D.C. This voltage is fed to the analog to digital converter (ADC) of the microprocessor board for further processing. Microprocessor board: The microprocessor board (6) used for the purpose are commercially available and generally comprises of following parts: 8 or 16 bit central processor, one or more no. of 2-64 KB of Read Only Memory, one or more no. of 2-64 KB of Read and Write memory, one 8 to 256 channel analog to digital converter using combination of 8 or 16 channel ADC(8) in cascade form, one or more no. of parallel port, one or more no. of serial port (9) one no. of programmable interval timer , one no. of keyboard interface and one or more stabilized power supply(7)powered from surface. (ii) Data link: The data link (2) is voice grade twisted pair copper cable of 0.5-1.0 millimeter (mm) diameter. In the case of multi channel link, line driver is provided at both ends. And in case of unichannel in the form of loop, T type connections are taken from this loop as required. There is a common line driver at surface data station and one line driver at the end of each T. A switching device is provided for poling of each underground data station by the surface data station. The line driver converts the TTL (transistor transistor logic) level signal into a maximum of ± 25 volt signal. At the receiving end the signal so received is converted to TTL level signal. With the technique developed it is possible to employ simple line drivers upto distance of 4 km. for mining applications. (iii)Surface data station: The surface data station is shown in figure 4 while its connection with data link and interconnection between two microprocessors is shown in figure 5. The surface data station comprises of (a) two microprocessor boards (10), (b) one PC-XT or PC/AT (IBM compatible) (11), (c) intrinsically safe power supply (12) and (d) uninterruptible power supply system (13).The two microprocessor boards are similar to the boards as used for underground data station except the surface microprocessor board does not have the analog to digital converter or digital to analog converter. Both the microprocessors remain in ON position all the time while one remains in operation. The other remains as standby. (iv)Intrinsically Safe Power Supply: The intrinsically safe power supply has been shown in figure 6. The power supply comprises of the following blocks 1. Signal Generator (17) 2. Amplifier (18) 3. Surface transformer (19) with associated circuitry 4. Underground transformer (27)with associated circuitry. 1. Signal generator (17): This produces an audio frequency in the range of 2-4 KHz. This audio frequency signal is fed to the second block i.e. amplifier (18) as shown in figure 6. 2. Amplifier (18): The amplifier is shown in figure 6. The audio frequency (A.F.) signal received from the signal generator is then amplified and fed as input to the surface transformer (19) . 3. Surface transformer with associated circuitry: The third block consists of transformer(29) limiting Resistance (20), zeners (21, 22, 23, 24), bridge rectifiers (25,26) and silicon controlled rectifier (28). The transformer (19) has the turn ratio of 4:100 to 8:1000 while the limiting resistance (20) (440-500 Ohm, 10W) is put across the arm. There are four zeners FZ60 (21,22,23,24), two each placed back to back. Each bridge rectifier (25) and (26) has four diodes (2-6 Amp. rating) . The SCR (28) used has the peak inverse voltage of 200-600V. The input received by the primary of the transformer gives an audio frequency output between 30-90 V and a current of 15-50 mA. This output is fed to the underground transformer (27) of intrinsically safe power supply. 4. Underground transformer with associated circuitry: The fourth block consists of transformer (27), filter circuit (29) and zeners (30). The underground transformer (27) has the turn ratio to suit various voltages required. Operation of the equipment: - The operation of the system is described with the help of figure 7 and 8 for multichannel and 7 and 9 for unichannel system, respectively. Intrinsically safe power needed for sensor, microprocessor boards and signal processor is fed in different units of time, in time division multiplexing (TDM) mode. Similarly, power to different data stations are fed in different time frames in TDM mode. In between these two time frames for two consecutive data stations, a time frame is added for transmission of data from underground to surface data station. Each time frame may vary from 1 millisecond to 100 milliseconds depending upon the data scan rate. When power to any data station is switched off and a time frame is kept free for data transmission, power is stored with the help of capacitors. This enables microprocessor based switching of power and data on same pair of conductor. While power is being sent to any particular data station and data is being transmitted by the data station, all the other data stations connected on same pair of conductor remain non-functional. The main advantage of the present invention are : 1. There are no flame proof enclosures underground; 2. There are no batteries underground; 3. No power is taken from 110 V underground source. 4. The equipment has higher degree of safety since only intrinsically safe power is used. 5. With microprocessor based switching, intrinsically safe power can be fed from surface without use of additional cable. We claim : 1. A data acquisition system useful for underground mines which comprises one or more underground data stations (1)( fig. 1), the said data station consists of appropriate sensor (4)(fig.3), output of the said data station being connected to the input of a signal processor (5)(fig.3), the said signal processor (5) being connected to an analog to digital converter (8)(fig.3) of an underground microprocessor board (6)(fig.3) through a data link (2)(fig.3), serial port (9)(fig.3) of the said underground microprocessor board being connected to a surface microprocessor 10)(fig.4) of surface data station (3)(fig.l), the said surface microprocessors being connected to a personal computer (ll)(fig.4), the said sensors, signal processor, underground and surface microprocessors and the personal computer all being connected to an stablised intrinsically safe power supply (7)(fig.7). 2. A data acquisition system as claimed in claim 1, wherein the sensors used are those capable of sensing methane, carbon monoxide, air velocity, pressure, temperature. 3. A data acquisition system as claimed in claims 1 & 2 wherein the signal processor is an op-Amp IC 741. 4. A data acquisition system as claimed in claims 1 to 3 wherein the microprocessor used consists of 8/16 bit central processor, one ore more 2-64 KB Read Only Memory, and Read and Write memory, one 8 to 256 channel analog to digital converter using cascading of 8/16 channel ADCs, one or more parallel / serial ports one programmable interval timer and keyboard interface. 5. A data acquisition system as claimed in claims 1 to 4 wherein the data link used is a voice grade cable of diameter in the range of 0.5 to 1.0 mm with a line driver at each end. 6. A data acquisition system as claimed in claims 1 to 5 wherein the data link is connected in multichannel or unichannel loop configuration. 7. A data acquisition system useful for underground mines substantially as herein described with the reference to the drawings accompanying this specifications.

Documents:

174-del-1995-abstract.pdf

174-del-1995-claims.pdf

174-del-1995-correspondence-others.pdf

174-del-1995-correspondence-po.pdf

174-del-1995-description (complete).pdf

174-del-1995-drawings.pdf

174-del-1995-form-1.pdf

174-del-1995-form-2.pdf

174-del-1995-form-4.pdf

174-del-1995-form-9.pdf

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