Water well monitoring system

#The present invention relates generally to the measurement of water levels in wells, and, more particularly, to a self-powered 4-20 mA loop hydrostatic pressure based well monitoring apparatus and method.

#In many regions of the U.S. and other countries, water resources are limited and privately owned wells are located in places without access to electrical power. Water conservation and preservation of water tables in these regions is important. Furthermore, monitoring of well contents and conditions for regulatory purposes, such as U.S. Geological Service programs and other programs, for example, is becoming increasingly important.

#Currently, the water levels in many privately owned wells are not being monitored at all, and many that have been monitored have been monitored manually by the measuring tape or “stick” method. For instance, when a weighted, chalked string or steel tape is lowered into a well, the wetted chalk changes color. Provided that the weighted end of the string or tape is accurately lowered to the floor of the well, the color transition indicates the height of the water level after the string or tape is pulled back out of the well. In contrast, many wells on industrially owned properties and well-funded municipalities and utilities have been monitored by automated systems incorporating hydrostatic head pressure sensors that provide 4-20 mA signal outputs. Compared to these automated systems, the stick method is relatively inaccurate and labor intensive.

#FIG. 1 is an illustration of an exemplary water well monitoring system according to the present invention (as installed in a well);

#FIG. 2 is a block diagram of the system of FIG. 1; and

#FIG. 3 is a flow diagram of an exemplary water well monitoring method for the system of FIG. 1 according to the present invention.

#FIG. 1 is an illustration of an exemplary water well monitoring system 100 according to the present invention as installed in a typical operating environment such as, for example, a well 110. In general, a hydrostatic pressure sensor 120 measures a pressure exerted by a column of fluid (or “head pressure”) and generates a signal corresponding to the pressure. Depending on the density of the fluid, among other things, the pressure signal is used to determine the height 140 of the column (i.e., the fluid level). To this end, the system 100 includes a 4-20 mA loop-powered hydrostatic pressure sensor 120, which is a model No. FMX 167 sensor available from Endress+Hauser, Inc. of Greenwood, Ind. Accordingly, Endress+Hauser, Inc.'s application notes TI 351 P/24/ae/04.01 © 2001 Endress+Hauser, Inc. for the FMX 167 are incorporated herein by reference. However, it is noted that other suitable hydrostatic pressure sensors may be used in alternative embodiments. Furthermore, it will be appreciated that the pressure sensor 120 is but one of a number of alternative process instruments that in alternative embodiments may provide a suitable low power, 4-20 mA output corresponding to a measured variable to the measuring unit 160 (which is discussed in further detail below).

#In the exemplary system 100, the pressure sensor 120 is configured to be submerged in the well water 130. A cable 150 couples the pressure sensor 120 to a measuring unit 160 in a known manner. In general, the measuring unit 160 is configured to receive a 4-20 mA signal from the pressure sensor 120 and generate a corresponding human perceptible indication of the water level 140. Measuring unit 160 has an indicator 170 on a front face 180 and a standard, normally open push-button switch 190 on a surface 200 of the measuring unit 160. While the exemplary indicator 170 shown in FIG. 1 includes a liquid crystal display (“LCD”), it is noted that in alternative embodiments the indicator may include a light emitting diode (“LED”) display, a paper printer, a sound generating device, or any other suitable device for providing an indication of the water level 140. Measuring unit 160 may be configured to provide various electronic output signals, such as discrete type (e.g.open collector) for alarms at specific low water points,and/or wireless transmission of data by various telemetry means, such as wireless internet, satellite, or any other suitable means. Measuring unit 160 is discussed in further detail below.

#FIG. 2 is a block diagram of the system 100 of FIG. 1. As shown, the pressure sensor 120 (discussed above) is coupled to the measuring unit 160 in a 4-20 mA type loop to receive power therefrom and to provide a 4-20 mA signal thereto (see VE and IL). In the exemplary embodiment of FIG. 2, all of the components of the measuring unit 160 are enclosed within the same housing. It should be appreciated that this provides portability and ruggedness. Measuring unit 160 includes a processing unit 210, which includes the indicator 170 (discussed above). The processing unit 210 is configured to receive the 4-20 mA signal from the pressure sensor 120 and generate the appropriate corresponding signals for causing the indicator 170 to provide the corresponding human perceptible indication of the water level 140. Accordingly, the processing unit 210 is implemented with the standard hardware (“H/W”) and software (“S/W”) of the model No. RIA 261 process device available from Endress+Hauser, Inc. of Greenwood, Ind. Endress+Hauser, Inc.'s application notes TI 083R/24/ae/04.01 © 2001 Endress+Hauser, Inc. for the RIA 261 are incorporated herein by reference. As shown in FIG. 2, the positive or “+” terminal of the exemplary FMX 167 pressure sensor is coupled to terminal No. 3 of the exemplary RIA 261 H/W and the negative or “−” terminal of the FMX 167 sensor is coupled to terminal No. 4 of the exemplary RIA 261 H/W. It will be appreciated that in alternative embodiments, the processing unit 210 may be implemented with any other suitable hardware and/or software.