Patent Document

CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of prior application Ser. No. 09/046,393, filed Mar. 23, 1998 now abandoned, priority from the filing date of which is hereby claimed under 35 U.S.C. § 120. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to automatic meter readers, particularly automated chart recorders. 
     BACKGROUND OF THE INVENTION 
     Chart recorders sense physical parameters, such as fluid flow, volumes, pressure and temperature, and are often used in oil and gas producing, processing, and transportation facilities. These chart recorders consist of sensing elements mechanically linked to actuate pens that mark on a chart. The chart rotates or is otherwise advanced by a chart drive. The pens travel across the chart, marking the variables on the advancing chart paper. 
     Past attempts to capture the sensed variables at the chart recorders have included linkage driven linear or rotational displacement elements as for example the proposal found in U.S. Pat. No. 4,414,634 issued Nov. 8, 1983. This method requires moving parts such as linkage connections that are subject to wear. These devices require unique calibrations from those normally performed on the chart recorder. 
     Other attempts have included the use of a camera and supporting hardware mounted in front of the chart to record and disseminate the chart values as disclosed in U.S. Pat. No. 4,837,708 issued Jun. 6, 1989. Size, complexity, cost, potential for tampering or theft and reliability would have hampered the adoption of this method. 
     A chart digitizing system pioneered by the patent applicant has been developed using existing pen position determining art, and proprietary software to enable the manual tracing of the chart lines once the chart has been created, taken off and placed on the digitizing tablet. 
     SUMMARY OF THE INVENTION 
     Conventional chart recorders suffer disadvantages in that there is an inherent delay in the getting the information from the chart and into the system. The chart typically has to be completed, taken off, interpreted before getting the results. The delay presents challenges and difficulties in optimizing operations needing the data. 
     The invention differs substantially in that the invention allows the pen positions to be detecteted and logged at the recording or indicating instrument in real time. 
     There is therefore provided in accordance with an aspect of the invention an automatic meter reader, comprising a meter having a movable arm, the movable arm having an indicator tip, the indicator tip being movable through a range of positions in response to the meter sensing a physical parameter, and a digitizer mounted on the meter, the digitizer having a digitizing grid positioned adjacent the indicator tip for sensing the position of the indicator tip. 
     The use of the invention allows the chart recorder pen positions to be detected and processed as the chart is being created. The digital data can be stored to memory and communicated to other devices. The information is then readily available for use through a variety of common interfaces. 
     Equipping the marking devices so their position can be detected at the point of contact on the chart or chart backing surface allows a direct correlation between the chart recorded data and the logged values without special calibration efforts on the recorder. 
     This system has the advantage of operating as a dual system where the ink on paper chart can be retained as the pen functions are logged. 
     The system has the further advantage that the position sensing grid and electronics has no moving parts to wear. The system will be accurate, reliable, be easy to produce and install. 
     These and other aspects of the invention are described in the detailed description of the invention and claimed in the claims that follow. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     There will now be described preferred embodiments of the invention, with reference to the drawings, by way of illustration only and not with the intention of limiting the scope of the invention, in which like numerals denote like elements and in which: 
     FIG. 1 is a perspective view of a chart recorder and digitizer according to an embodiment of the invention; 
     FIG. 2 is a front view of a chart recorder showing location of movable arms according to an embodiment of the invention; 
     FIG. 3 is a schematic section through the chart recorder and digitizer of FIG. 1 showing the principal components of an embodiment of the invention; 
     FIG. 4A is a side view of a set of three movable arms with pens according to the invention; 
     FIG. 4B is a top view of the movable arms of FIG. 4A; 
     FIG. 4C is a bottom view of the movable arms of FIG. 4A; and 
     FIG. 5 is a detail of a pen adaptor according to an embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1 shows an automatic meter reader which has two main parts, a conventional chart recorder  10  that has been modified to incorporate a digitizer  12  and chart pen adaptor  18 . The chart recorder  10  may for example be a DRI-FLO II (tm) chart recorder, or an ITT Barton Model 202A or 208A differential pressure recorder, but this invention is not restricted to the particular chart recorder, and may be used on a variety of chart recorders and other meters that have a movable arm. 
     As shown in more detail in FIGS.  2  and  4 A- 4 C, the chart recorder  10  has three mechanically actuated movable arms  14 A- 14 C which are mounted on pivot points  25 A- 25 C within a housing  15 , in which is installed a backing plate  24 . The backing plate  24  is installed in conventional manner. Each movable arm  14 A- 14 C terminates in an indicator tip which includes a pen tip  16 A- 16 C and pen adaptor  18 A- 18 C respectively. Ink reservoirs  29 A- 29 C lying on the movable arms  14 A- 14 C respectively in conventional fashion provide ink through ink capillaries  31 A- 31 C respectively to the pen tips  16 A- 16 C respectively. The chart pen adaptors  18 A- 18 C are located at the end of each movable arm  14 A- 14 C respectively. The chart pen adaptors  18 A- 18 C may be each an electromagnetic coil  27  as illustrated in FIG. 5, having an open core through which the pen tips  16 A- 16 C extend respectively into contact with chart paper  20  during operation. The electromagnetic coils  27  may be glued, crimped or otherwise fastened to the movable arms  14 A- 14 C. The inner movable arm  14 C has an angled pen tip  16 C, e.g., at 45° to the vertical, to allow it to fit with the other pen tips  16 A,  16 B. 
     The chart recorder  10  illustrated senses gas flow through a dry gas flow sensing assembly  22  connected via a line  30  to a well. In response to gas flow (or other parameter being sensed) in a line (or other device) being monitored, the indicator tips  16 A- 16 C move through a range of positions, typically an arc, in response to the meter sensing the physical parameter. The chart  20  rotates about a spindle  32  in the meter  10 . Each movable arm  14 A- 14 C follows a different arc across the chart in close proximity to each other. 
     Digitizer  12  is mounted on the meter  10  by fitting the digitizer  12  into an opening  26  in the backing plate  24  of the meter  10 . The digitizer  12  has a digitizing grid  28  positioned adjacent the indicator pen tips  16 A- 16 C for sensing the position of the indicator pen tips  16 A- 16 C. Digitizing grids themselves are well known, and any of various types may be used in the operation of the invention, although the one selected may require modification to fit into a particular meter. In addition, the digitizing pen typically used with a conventional digitizer is replaced by one or more of the chart pen adaptors  18 A- 18 C mounted on the movable arm of the meter  10 . 
     The digitizing grid  28  may be affixed to the chart backing plate  24  in any of various ways, such as by being held by screws. The chart pen adaptors  18 A- 18 C transmit signals to the digitizing grid  28  in known manner. Conventional digitizing electronics and modified conventional programming detects the pen adaptor positions from the meter  10  and converts the pen adaptor positions into an electrical signal representative of the pen position or into a digital format. 
     A cordless, electromagnetic tablet digitizer incorporating a grid and controller such as the Mutoh America Pen System available from Mutoh America Inc. of Phoenix, Ariz., may be used as the digitizer  12 . There are numerous digitizers that may be adapted for mounting on a chart recorder in accordance with this invention, such as the SummaSketch (tm) digitizer available from Summagraphics Corporation of Seymour, Conn., or the UD-Series graphic tablet available from Wacom Technology Corporation of Vancouver, Wash. The conventional digitizer  12  is provided with the pen adaptors  18 A- 18 C to fit the movable arms  14 A- 14 C and modified shape to fit the backing plate  24 . The digitizer has built in programming which may be suitably modified to suit the particular application. For example, the PSC5M (tm) or PSC6 (tm) pen system controller products of Mutoh America may be used. As contained in the Mutoh America chart pen, the signal from the pen adaptors  18 A- 18 C may be frequency encoded to contain pen switch information (pen up or down, as well as side switch states). The digitizer  12  may incorporate a conventional RS-232 communications port or conventional removable memory card slot  34 . Other data interface devices may be used, including a transceiver for remote reading and interrogation of the digitizer  12 . The digitizer  12  acquires data by sensing the position of the pen adaptors  18 A- 18 C on the meter  10 . 
     The digitizer  12  has particular application to circular chart recorders used to determine fluid flow. As shown in FIG. 1, the chart backing plate  24  is replaced or modified to include an opening  26  to contain the digitizing grid  28  which may be etched on to a printed circuit board or screened on a Mylar (tm) grid or other device. In the Mutoh America digitizer, the amplitude and frequency of the received signal on individual sensor grid lines contain the information required to determine pen location, switch status and pen pressure. The system may be retrofitted to existing recorders or enhance newly produced or rebuilt chart recorders with the ability to log the data as it is created. The device can also be applied to indicating instruments and chart recorders of the strip chart or drum variety and digitize the pen positions for any of the variables indicated or recorded. There should be no metal between the pen adaptors  18 A- 18 C and digitizing grid  28  if an electromagnetic coil is used as the pen adaptor  18 A- 18 C. The pen adaptors  18 A- 18 C may be passive or active (powered). If the pen adaptors  18 A- 18 C are powered then the power is supplied in the conventional manner from the digitizer  12  along wires that are themselves conventional but are adapted for this invention by running the wires along the movable arms  14 A- 14 C. In some applications, only a single movable arm  14 A, with single pen adaptor  18 A and pen tip  16 A is required. The invention may be readily adapted to any number of movable arms. 
     The digitizer  12  is programmed to sense the pen or indicator positions on the meter  10  and process those signals into time stamped, digital data that can be stored and made available to other devices through the interface  34 . The meter  10  may also be an instrument that just indicates rather then record (such as pressure gages, speedometers, etc.) In this instance, the indicator tip is a non-marking indicator. The digitizer  12  includes conventional digitizer features such as memory for data storage and power circuitry for low power operation with an external battery pack. 
     Resolution of the position of the pen may be chosen to suit the application, but may for example be 1016 points per inch, with 0.01 inch accuracy in the vertical position of the pen or 0.02 inch in the 45 degree position. 
     The digitizer  12 , when used with more than one pen indicator, may poll the pen indicator positions one pen at a time, each uniquely identified as separate pens. By reading two pens in a gas recorder, wherein both differential pressure and static pressure were measured, would be enough to allow calculation of the gas flow, provided the temperature was manually input or otherwise entered into downstream gas volume calculation software. 
     A person skilled in the art could make immaterial modifications to the invention described in this patent document without departing from the essence of the invention that is intended to be covered by the scope of the claims that follow.

Technology Category: 3