Are You Looking for a pH Controller With These Features?

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Maintaining pH in water, chemical solutions, soil or any other media is vital for many scientific and industrial purposes. A pH controller lets you keep the pH within a specific range automatically. When the pH is outside the range, the controller allows something that amends the pH into the material being monitored. The pH should balance (in theory), and all should be well. Like most industrial tools, pH controllers come with a few options that can make your job much easier.

Automatic Temperature Compensation

The temperature of a solution affects its pH, which is frustrating if you're trying to measure the true pH of just that solution with no interference. Automatic temperature controllers measure both pH and temperature and convert the final pH value to what it would be if the temperature of the solution were at a standard temperature, instead of what the temperature was when you took the initial measurement. The automatic temperature compensation feature requires calibration to set the upper and lower parameters for that particular substance.

Proportional Control

When the pH of a solution becomes too acidic or basic, with values falling outside the tolerance range that you want, the controller needs to allow that amending solution to flow in. This should make the pH of the original solution move back into the acceptable range. However, you want the flow to stop when the pH is back in range, and sometimes the way a pH controller works doesn't allow for that detail. Rather, it simply lets the amending solution flow in at a constant, low level, and it's forever adjusting how much flows in (just a little too late as the pH value has to go out of range yet again for the controller to sense the need for an adjustment).

To avoid this, you need to look for a controller that offers proportional control. This type of control lets the amending solution flow in not only at different rates but also at different times. When the pH is within the acceptable range, the flow shuts off. It's only when the monitored pH goes out of range that the flow starts again, in proportion to the deviation from the range.

Hysteresis Bands

Hysteresis bands aren't physical bands. They're settings (like a band on a spectrum) on the controller that allow you to set upper and lower limits for the flow of the amending solution that are at different pH values than the ones that delineate the acceptable pH range. This is to control something called hunting, where the controller essentially hunts for the right pH. The hysteresis bands let you set the flow of the amending solution to end when the pH reaches a value that's still inside the acceptable range. This gives the controller a time buffer. While the pH may continue to go out of whack, the controller at least gets a break and isn't constantly turning on and off rapidly.