AP109A

AP109A - Electronic water-level measuring device.

Info

Publication number: AP109A
Application number: APAP/P/1989/000154A
Authority: AP
Inventors: Michael Andrew Peart; Victor Joseph; Anton Meeussen
Original assignee: Botswana Tech Centre
Priority date: 1989-02-28
Filing date: 1989-02-28
Publication date: 1991-02-23
Also published as: AP8900154A0

Abstract

A water-level measuring device intended to be installed in a borehole, which is composed of a cable-and pipe sub-assembly, and an electronic unit sub-assembly. The cable and pipe sub-assembly contains a multi-core cable composed of a number of insulated conductors to which electrode pairs are mechanically fastened and electrically connected at regular intervals along the length of the cable. The electronic unit sub-assembly contains an input for one conductor from each electrode pair, an electronic processing unit and a number of indicator lights to display the water level reading.

Description

WATERLEVEL MEASURING DEVICE

The present invention relates to a device for indicating the water level especially in a borehole.

Various types of level indicators are known in the prior art for providing information regarding the depth of liquid in a well or tank. However, problems have arisen in the viewing of the depth indication given by such devices because of their relative complexity, in particular it is difficult to read from a remote position.

The use of multi-electrode resistance probes has been proposed but has up to now not been commercialized. (see How to Measure Liquid Interface Levels (ISA Journal Vol, 5 No. 1 pp. 60 63). The purpose of the present invention is a device to measure the water level in borehole using simple electric means and as power source a conventional battery of low voltage. This makes the device particularly suitable to be installed permanently in boreholes in remote areas. The device is easy to install and enables a reading of the water level in a borehole.

According to the invention the waterlevel measuring device consists of a cable, a pipe sub-assembly and an electronic unit sub-assembly. At regular intervals along the length of the cable are electrodes connected to conductors in the cable and the electronic unit contains an input from each electrode pair. The waterlevel reading is displayed by a number of indicator lights.

The cable sub-assembly is a multi-core type cable with a number of insulated conductors inside. Each electrode pair is mechanically fastened and electrically connected to two conductors in the cable. One conductor may be common for supplying power to all the electrodes but the other conductor of an electrode pair is used as input for the electronic unit to display the water level by lighting the pertinent indicator light.

The borehole water	indicator of	the present invention	can
indicate the presence of water at	20 different levels	in a
borehole up to 200	meters deep at	a push of a button.	the
lifetime of the low	voltage battery	depends on frequency of	use,
but will be at least	a year.

The principle of operation of the present invention is that the ^c c

resistance between the electrodes in an electrode pair depends on Q the presence of water between them. Lowering of resistance occurs when water is present and this is sensed within the electronic unit. In this way the electronic unit can detect which electrode pairs are immersed and which are dry and hence display the actual water level.

The invention is further described by way of example with references to the accompanying drawings in which:

Figure 1 shows the pipe sub-assembly and the electronic subassembly which together constitute the waterlevel measuring device.

Figure 2 shows the waterlevel sensor electronic box.

Figure 3 shows the wiring diagram in the electronic box.

Figure 4 shows the cable.

Figure 5 and 6 shows the electronic circuit diagram.

In figure 1 MTL20 shows the pipe sub-assembly and F9 shows the box containing the electronic unit sub-assembly. A cable E3 is installed in the pipe and connected to the box by connection E6. the pipe is provided with openings in the side and the end is welded closed.

Figure 2 shows the front and the side views of the electronic unit box. The panel on the front view shows twenty level indicating lights (B16) respectively for 0.5, 1, 1.5, 2, 2.5, 3, 4 up to 34 meters. At the bottom at the right is a light indicator to light when the water is at pump level and at left side is a light indicator (B17) to warn when the battery has to be replaced. In the middle is a button (E1) which is pressed to light the light indicators.

Figure 3 shows the wiring diagram in the electronic box. The multi-core cable has conductors coloured in different colours. One of the conductors (E9) is connected to the battery while the signals from other conductors are processed to control the appropriate light indicators. Fig. 4 shows the cable and the connecting spots for the electrodes.

Figure 5 and 6 show a convenient circuit diagram to be used for lighting the light indicators in the electronic box. The waterlevel measuring device of the present invention is intended for permanent installation in boreholes. It enables the operator to obtain an instantaneous reading of the water level at any given time. Furthermore the cable with the electrode pairs can be lowered or raised for inspection through the pipe which is strapped onto the rising main on the borehole pump.

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Claims

1. A waterlevel measuring device composed of a cable and pipe sub-assembly, and an electronic unit sub-assembly, whereby the cable and pipe sub-assembly contains a cable composed of a number of insulated conductors to which electrode pairs are connected along the length of the cable, and whereby the electronic unit sub-assembly contains an input for one conductor from each electrode pair, an electronic processing unit and a number of indicator lights to display the water level reading.

2. A water-level measuring device according to claim 1 in which the cable is a multi-core type cable having multi-coloured conductors and to which at regular intervals along the length of the cable, an electrode pair is mechanically fastened and electrically connected to two conductors in the cable.

3. A water-level measuring device according to claim 1 in which the cable is installed in a plastic guiding pipe in order to facilitate installation and inspection.

4. A water-level measuring device according to claims 1, 2 and 3 in which the end of the plastic pipe is welded closed and holes are drilled near the closed end.

5. A water-level measuring device in which the power is supplied by a low voltage battery and in which one of the conductors in the cable connects the power supply to one of the electrodes of each pair of electrodes situated along the length of the cable.

6. A water-level measuring device according to one of the claims 1 to 5 in which the water level is displayed by lights on a panel board and can be read instantaneously by pressing a button.

7. A water-level measuring device according to one of the claims 1 to 6 intended to be permanently installed in boreholes.