mod-EC

Procedure

Following good lab procedures is important to obtain the best results while also staying safe. Aside from safety considerations, the following is a step-by-step process calibration:

1. Collect all the materials needed: calibration solutions, clean water, towels, equipment, etc.
2. Rinse the probe in clean water. RO/DI, deionized, or distilled water is best. Tap off excess water drops trapped in the probe tip and blot dry. For lab probes, do not touch the electrodes inside the glass loop
3. Pour some calibration solution into a separate container. It should be enough to fully submerge the tip of the probe, then submerge the probe.
4. Continually take measurements, watching for the measurement to stabilize. Eventually, only the third decimal place will vary from measurement to measurement. When the reading stabilizes, have the module calibrate itself for the solution.
5. Safely dispose of the calibration solution and clean or dispose of the container.
6. Repeat steps 2 through 5 for each calibration point. When calibrating, use the labeled value, not the temperature-adjusted value.

Calibration Types

The module supports three methods of calibration.

Single Point

Single point is the least useful and should generally not be used. It uses one point and is only accurate for a small range around that one point.

Dual Point

Dual point calibration is used for measuring between two set points. To determine the points, decide on the lowest point to be measured and the highest point. After calibrating between those two points, the measurements can be expected to be very accurate between them. Outside the two points, the measurements will get increasingly inaccurate the further from the calibration points the measurement gets.

Triple Point

The module’s response is not perfectly linear throughout the entire range of possible measurements. To get the most accurate measurements over the widest range, triple point calibration can be used. It is similar to dual point, but uses three points rather than two. A good starting point for a very large range would be a low of 0.5 mS, a mid of 1.0 mS, and a high point of 10.0 mS.

Precedence

The module will select the best calibration type from the available calibrated points as follows:

1. If there are high, mid, and low points, it will use triple-point calibration to calculate the result.
2. If there are high and low points, it will use dual-point calibration to calculate the result.
3. If there is a single-point calibration data, it will use single-point calibration to calculate the results.
4. No calibration points used will result in an uncalibrated measurement.

Calibration data is stored on the module. Measurements will automatically use calibration data; there won’t be a change until both a high and low point have been entered.

More Explanation

The same solution can measure over a relatively wide range as the temperature changes. As an example, suppose a tank of water needs to maintain an EC value of 1.0 mS/cm. The tank is exposed to the weather, and the temperature increases and decreases throughout the day. The conductivity will also increase and decrease as the temperature changes. To have a reliable method of comparing the current conductivity to the setpoint, the temperature must be compensated for. This is done by choosing a particular temperature to adjust all readings to. This is typically 25 °C. The compensation would have the effect of changing the conductivity measurement taken at the current temperature and adjusting it so that it would represent what it would have been at 25 °C.

Several points of data are needed for this calculation:

• The solution’s current temperature
• The temperature to adjust to
• The temperature coefficient

The solution’s temperature and the temperature to adjust to have been discussed above. The temperature coefficient is the percent change per degree. The coefficient is different for every solution and is determined by its composition. Sometimes the solution being measured is known, and a temperature calibration characterization can be done, oftentimes the exact composition isn’t known, and an estimation is required. For freshwater, the most typical coefficient is 0.019. For seawater, it is around 0.021, and for pure water, 0.052.

Because the coefficients are estimations, they introduce a small amount of uncertainty. It is important to note that a chart of the measurement with varying temperature won’t be perfectly flat, indicating that all the temperature effects have been fully eliminated. It will still move with the temperature, but not nearly as much.

Wiring directly to a host controller

Using a mod-ISO module for isolation

1.

🔽 Install Arduino IDE

Install the Arduino IDE

2.

📦 Install the library

Start the Arduino IDE, press the Sketch menu, and then Include Library > Manage Libraries. Search for Microfire_Mod-EC and install the library.

3.

🔢 Code

Below is the Basic example. It can be found in File > Examples > Microfire_Mod-EC > Basic in the Arduino IDE.

#include <Microfire_Mod-EC.h>
Microfire::Mod_EC::i2c ec;
void setup() {
	Serial.begin(9600);
	Wire.begin();
	ec.begin();
}

void loop() {
	ec.measureEC();
	Serial.println((String) ec.mS + " mS/cm");
	delay(1000);
}

4.

➡️ Upload the code

Pick the board and port, then Upload the code.

5.

🔎 View the output

Open the Serial Monitor, measurements should be displayed in the monitor, with updates every second.

6.

📒 Documentation

The library is documented here:

PDF DOC HTML

1.

📦 Install ESPHome

Follow the instructions on the ESPHome website.

2.

⌨️ Start a project

Type esphome wizard mod-ec.yaml in the terminal. Make sure the path on the terminal is where you want the project to be. Follow the steps, and there should be a .yaml file in the directory you ran the command in. For this write-up, it will be mod-ec.yaml. If you type esphome compile mod-ec.yaml you should see the project compile.

3.

🔢 Code

The YAML file should be changed to the following:

esphome:
  name: microfire-mod-ec
esp32:
  board: esp32dev
  framework:
    type: arduino
logger:
api:
ota:
wifi:
  ssid: !secret wifi_ssid
  password: !secret wifi_password
captive_portal:

# import the mod-ec component
external_components:
  - source:
      type: git
      url: https://github.com/u-fire/ESPHomeComponents/

# https://esphome.io/components/i2c.html
i2c:
  sda: 21
  scl: 22

sensor:
  - platform: mod_ec
    id: ec
    name: EC

button:
  - platform: template
    id: ec_calibrate_low
    name: EC Calibrate Low 0.5
    icon: mdi:format-vertical-align-bottom
    on_press:
      lambda: |-
        id(ec).calibrateLow(0.5);

  - platform: template
    id: ec_calibrate_mid
    name: EC Calibrate Mid 1.0
    icon: mdi:format-vertical-align-center
    on_press:
      lambda: |-
        id(ec).calibrateMid(1.0);
  - platform: template
    id: ec_calibrate_high
    name: EC Calibrate High 5.0
    icon: mdi:format-vertical-align-top
    on_press:
      lambda: |-
        id(ec).calibrateHigh(5.0);
  - platform: template
    id: ec_calibrate_reset
    name: EC Calibrate Reset
    icon: mdi:restore
    on_press:
      lambda: |-
        id(ec).calibrateReset();
  - platform: factory_reset
    name: Restart with Factory Default Settings

Wiring

1.

📦 Install the library

The Python library can installed through pip in a terminal:

pip3 install Microfire-Mod-EC

Typing python3 -m Microfire_Mod_EC.shell will start the shell application and give access to all features and functions of the module. Type help to see a listing of the commands available.

2.

🔢 Code

Create a python script and run the following sample code.

import Microfire_Mod_EC
ec = Microfire_Mod_EC.i2c()

ec.begin()
ec.measureEC()

if ec.status:
  print("Error: " + ec.status_string[ec.status])
else:
  print("{:.2f}".format(ec.mS), end='')
  print(" mS/cm °C")

3.

📒 Documentation

The library is documented here:

PDF DOC HTML