WFX-40 Submersible Fine Well Water Level Gauge

1. Overview
1.1 This instrument is designed and manufactured in compliance with the National Standard GB/T11828.1-2002, and is widely used for measuring water levels in surface water, groundwater, and dam piezometers.
1.2 This instrument is a single-float self-retrieving cable water level gauge (hereinafter referred to as the water level gauge), which, during operation, uses only one measuring cable to pull a float to track the rise and fall of water levels, thereby achieving automatic water level measurement.
1.3 This model instrument is suitable for use in locations where the inner diameter of the pipe is not less than 70-150mm, with a burial depth of 10-500m. The central axis of the well pipe must be straight, and the inner wall of the well pipe must be smooth with no ridges or bumps.
1.4 This instrument's water level encoder is a low-torque, lightning-resistant type (microswitch contact power of 5A/250V) absolute encoder, equipped with a gold-plated waterproof aviation socket. The instrument boasts stable and reliable performance with no temperature or time drift.

2. Composition and Working Principle
This model instrument is composed of a water level encoder, measuring wheel, measuring cable, float, and self-retrieval cable device; the self-retrieval cable device includes a winch wheel, winch shaft, winch cable, fixed pulley set, movable pulley set, weight, upright support plate, base plate, and protective cover; the water level encoder of the instrument is mounted on the upright support plate, and the measuring wheel is mounted on the shaft of the water level encoder; the winch shaft of the self-retrieval cable device is mounted on the support plate; the winch wheel is mounted on the end of the winch shaft; the movable pulley set is mounted on the weight; the fixed pulley set is mounted on the support plate through individual brackets; the starting end of the winch cable is mounted on the winch shaft, and the other end passes through the fixed pulley 1, movable pulley 1, fixed pulley 2, and movable pulley 2 before passing upward through the mounting hole of the support shaft and being fixed to the support shaft; the instrument protective cover is connected to the base plate with four fixed screws. The measuring cable is wound in the groove of the winch wheel, and its lead-out end is wound counterclockwise around the water level wheel before passing downward through the line hole of the instrument base plate and connecting to the float; the function of the self-retrieval cable device is to generate a constant force for tightening and automatically retrieving the measuring cable, allowing the float to operate at the normal draft depth.
The principle of operation is as follows: When the water level is stationary, the float remains at rest on the water surface, and the instrument's weight hammer hovers at the corresponding height, with the encoder output corresponding to the water level height. As the water level drops, the float moves downward along the center of the well pipe in sync with the water level change, pulling the measuring cable downward. This drives the measuring wheel to rotate counterclockwise while simultaneously turning the winch wheel and shaft clockwise, lifting the weight hammer to the corresponding height. The water level encoder outputs a value corresponding to the change in water level. When the water level rises, the float moves upward along the center of the well pipe to the corresponding position, following the water level increase. Under the weight hammer's influence, the winch cable drives the winch shaft and wheel to rotate counterclockwise, straightening and retracting the measuring cable, causing the measuring wheel to rotate clockwise. This makes the water level encoder output a value corresponding to the rise in water level, completing the automatic tracking measurement of the water level.
This instrument's water level encoder outputs Gray code 10 to 13 bits, connected to an external display or computer via a multi-core aviation connector and cable, capable of measuring water level fluctuations of 10 to 80 meters.
This instrument requires an additional special lightweight suspension cable to be attached to the overlong suspension part when the burial depth exceeds 80 meters for groundwater level measurement.

3. Well Logging Construction Requirements
3.1 Well logging is typically composed of multiple sections of fixed-length steel pipes (or engineering plastic pipes, concrete pipes) connected together. Each section of well pipe is 2 to 6 meters in length. The joints of each pipe must be smooth and free of obstructions, with a gap of ≤2mm. The difference in height of the inner wall at the joint should be ≤1mm, and the geometric central axis of each section of well pipe should remain in a straight line without bending.
3.2 The well casing diameter should generally not be smaller than Φ70mm, with the water intake area approximately 1/10 of the well opening size. The joints between sections of well casing may not be sealed.

4. Main Technical Parameters
4.1 Water Level Range: 0-10m: 0-20m; 0-30m; 0-40m; 0-80m
4.2 Water Level Encoder Resolution: 1 cm
4.3 Measurement Accuracy: ≤0.2%
4.4 Float Diameter: Φ40mm; Φ50mm; Φ100mm available
4.5 Output Signal: Gray Code 10-13 bits (RS485 or 4-20mA interface optional)
4.6 Environmental Temperature: -10℃ to 85℃
Relative humidity; ＜90% (at 40℃).