What is a PID control for an EC measurement?

What is the purpose of PID control?

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 PID control work in this application?

1. Measurement (Input)

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

2. Comparison with setpoint

• De fout (error) wordt berekend:
  • 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.