What is a PID control for an EC measurement?

What is a PID control for an EC measurement?

What is the purpose of PID control here?
The purpose of PID control is to keep the EC value constant around a desired setpoint, e.g. 2.0 mS/cm.

If EC is too low → adjust pump with nutrients.
If EC is too high → dilute water or reduce dosage.

How does the PID control work in this application?

1. Measurement (Input)

  • An EC sensor continuously measures the current conductivity of the water.

2. Comparison with setpoint

  • The error (error) is calculated:
    • Error = Setpoint – Measured EC value

3. PID calculation

  • The controller calculates how fast and how much to adjust based on this error.
  • Proportional (P):
    • Direct response to the error.
    • The larger the error, the stronger the correction (e.g. more fertiliser dosing).
  • Integrative (I):
    • Corrects for permanent deviations.
    • If the EC remains slightly too low for a long time, it slowly increases the dosage.
  • Differentiating (D):
    • Looks at how fast the EC changes.
    • Inhibits rapid increases or decreases → prevents excess.

4. Control (Output)

  • The calculated correction is sent to e.g. a dosing pump or valve.

Example:

  • Setpoint EC = 2.0 mS/cm
  • Measured EC = 1.6 mS/cm → error = +0.4
  • PID controller EC3055:
    • Turns on the feed pump (proportional)
    • Keeps it on longer as error persists (integral)
    • Adjusts dosage if EC rises too quickly (differential)

At Nieuwkoop, we offer one of the most accurate EC controllers including PID control available which are also easy to use.