Calculate and Plot Reading of a Water Well Sensor

plot-water-well.py

"""
Calculate and Plot Reading of a Water Well Sensor

Simple software made for aiding in calculating the values that an analog voltage sensor will read from a series resistor
in a water column height sensor with a constant current output. The analog sensor happened to provide its output value
in percentage to the web API.

Used for a particular setup where a Shelly 2PM + AddOn Plus was reading the voltage of the resistor.

Author: Alexandre Vieira, 2023
"""

import numpy as np
from matplotlib import pyplot as plt
from scipy import interpolate

if __name__ == "__main__":
    RESISTOR = 510  # Ohm
    RESISTOR_MAX_POWER = 0.25  # Watt
    PROBE_CURRENT_MIN = 4e-3  # Ampere
    PROBE_CURRENT_MAX = 20e-3  # Ampere
    PROBE_HEIGHT_MIN = 0  # mH2O
    PROBE_HEIGHT_MAX = 4  # mH2O
    PROBE_HEIGHT_OFFSET = 20e-2  # meter
    SENSOR_VOLTAGE_MIN = 0  # Volt
    SENSOR_VOLTAGE_MAX = 10  # Volt
    WELL_DIAMETER = 1.5  # meter

    calc_curr = lambda height: np.interp(
        height,
        [
            PROBE_HEIGHT_MIN + PROBE_HEIGHT_OFFSET,
            PROBE_HEIGHT_MAX + PROBE_HEIGHT_OFFSET,
        ],
        [PROBE_CURRENT_MIN, PROBE_CURRENT_MAX],
        left=PROBE_CURRENT_MIN,
        right=PROBE_CURRENT_MAX,
    )
    calc_volt = lambda curr: RESISTOR * curr
    calc_pow = lambda curr: RESISTOR * curr * curr
    calc_perc_1 = lambda volt: np.interp(
        volt, [SENSOR_VOLTAGE_MIN, SENSOR_VOLTAGE_MAX], [0, 100]
    )
    calc_perc_2 = interpolate.interp1d(
        [SENSOR_VOLTAGE_MIN, SENSOR_VOLTAGE_MAX], [0, 100], fill_value="extrapolate"
    )
    calc_perc = calc_perc_2  # using second method to allow extrapolation
    calc_vol = (
        lambda height: np.pi * (WELL_DIAMETER / 2) ** 2 * height
    )  # assumes meters as input, thus result in cubic meters

    test_heights = np.linspace(0, 2.5, 100)

    current_values = calc_curr(test_heights)
    voltage_values = calc_volt(current_values)
    power_values = calc_pow(current_values)
    perc_values = calc_perc(voltage_values)
    vol_values = calc_vol(test_heights)

    def plot_in_subplots():
        fig, axs = plt.subplots(3, 1)

        axs[0].plot(test_heights, perc_values)
        axs[0].set_xlabel("Altura Água [m]")
        axs[0].set_ylabel("Medida Shelly [%]")
        axs[0].grid(True)

        axs[1].plot(test_heights, power_values)
        axs[1].set_xlabel("Altura Água [m]")
        axs[1].set_ylabel("Potência Resistência [W]")
        axs[1].hlines(
            y=[RESISTOR_MAX_POWER, RESISTOR_MAX_POWER / 2],
            xmin=test_heights.min(),
            xmax=test_heights.max(),
            linewidth=2,
            color=["r", "orange"],
            linestyle="--",
        )
        axs[1].grid(True)

        axs[2].plot(test_heights, vol_values * 1e3)  # m3 to l
        axs[2].set_xlabel("Altura Água [m]")
        axs[2].set_ylabel("Volume [l]")
        axs[2].grid(True)

        fig.tight_layout()
        plt.show()

    def plot_splines():
        fig, ax1 = plt.subplots()
        ax2 = ax1.twinx()
        ax3 = ax1.twinx()

        fig.subplots_adjust(right=0.85)
        ax3.spines.right.set_position(("axes", 1.1))

        fig.set_figwidth(12)
        fig.set_figheight(7)

        (h1,) = ax1.plot(test_heights, perc_values, "b-", label="Medida Shelly")
        ax1.set_ylabel("Medida Shelly [%]")

        (h2,) = ax2.plot(test_heights, power_values, "g-", label="Potência Resistência")
        ax2.set_ylabel("Potência Resistência [W]")
        h2_e1 = ax2.hlines(
            y=RESISTOR_MAX_POWER / 2,
            xmin=test_heights.min(),
            xmax=test_heights.max(),
            linewidth=2,
            color="orange",
            linestyle="--",
            label="Potência Tolerável",
        )
        h2_e2 = ax2.hlines(
            y=RESISTOR_MAX_POWER,
            xmin=test_heights.min(),
            xmax=test_heights.max(),
            linewidth=2,
            color="r",
            linestyle="--",
            label="Potência Máxima",
        )

        (h3,) = ax3.plot(
            test_heights, vol_values * 1e3, "c-", label="Volume"
        )  # m3 to l
        ax3.set_ylabel("Volume [l]")

        ax1.set_xlabel("Altura Água [m]")
        ax1.grid(visible=True, which="major", linestyle="-")
        ax1.minorticks_on()
        ax1.grid(visible=True, which="minor", linestyle=":")
        ax1.legend(handles=[h1, h2, h3, h2_e1, h2_e2], loc=(0.1, 0.6))

        plt.show()

    plot_splines()  # select which plotting method works best for you