Mod-pH

Summary | Use | Design | Ask a question | FAQ

Datasheet 📜

ℹ️ Summary

  • pH range of 0.001 to 14.000 pH units
  • Accuracy ±0.002 pH units
  • Resolution 0.001 pH units
  • Temperature compensated
  • I²C, UART, and USB interfaces
  • 1-Wire interface for DS18B20 temperature sensor
  • 25x15 mm for castellated or DIP mounting
  • Single, dual, and triple point calibration

🚀 Use


✒️ Design

Adding a module to your own design is straightforward. You'll need:

  1. bus connection to your controlling device (I2C, UART, USB)
  2. clean, isolated, power supply
  3. probe connection (U.FL, BNC, terminal block)

Some resources to get started:

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🤙 Ask a question

🤔 FAQ

Can I keep the probes in water all the time?

The short answer is yes, you can.

The longer answer is yes, but make sure you know the pros and cons. You can leave any probe submerged in water, in fact, the industrial versions are designed for exactly that. The lab versions are primarily designed for use and then storage, but can also be submerged.

For pH and ORP probes, it is best to think of them as disposable. They are inherently designed to slowly degrade. In these types of probes, there is a junction where a solution on the inside of the probe physically touches the water on the outside. Due to this water/water junction, the probes will slowly degrade over time.

Do I need isolation?

Yes.

The longer answer: You probably do. Cases where you definately will need isolation include using another EC, pH or ORP probe and when other electrical elements are in the tank (pumps, heaters, contact mixers). You may not need it in a small beaker with nothing else in it.

Isolation through Microfire devices also provides a stable power supply which is vital for accurate measurements, so even if you feel like isolation isn't needed, it may be a better choice to use it for the stability, and you also gain isolation for some unplanned for use-case that would require isolation.

How long should I go between recalibration?

There are a lot of factors involved in this one. It depends on how roughly the probes are being used. Are they subject to large temperature swings, harsh chemicals, fast flowing water, or drying cycles? All of those things will contribute to a faster recalibration schedule.

How accurate do you need your measurements to be? With light use, you might not see a pH measurement move more than a few tenths in several months. Is that within your error budget? Only you can say, given your specific application requirements and specific set of environmental factors. We can give general guidelines, but there is no simple, accurate answer.

When is temperature compensation needed?

For pH, it is required.

For pH and ORP, each particular solution will respond to temperature differently, so creating a temperature compensation formula is more difficult. You essentially need to know what you are meausuring and the temperature response curve. Sometimes this is possible and other times, it isn't. A sort of universal temperature compensation can be applied, but this only compensates for the resistance in the probe, which will also changing the readings.