pH/ORP METERS

How pH meters work

A pH meter works by measuring the electrical potential (voltage) generated by a solution and converting that measurement into a pH value. This process is called potentiometry and relies on a specialized probe containing two electrodes. 

The Measurement Process

1. 1. Immersion: When the pH probe is submerged in the solution being tested, the outer surface of the glass membrane comes into contact with the sample's hydrogen ions (H⁺).
   2. Ion Exchange: An ion exchange process occurs on both the outer and inner surfaces of the glass membrane. Hydrogen ions in the sample migrate into the outer layer of the glass, replacing some of the metal ions (like sodium or lithium) in the glass structure.
   3. Voltage Generation: Because the concentration of hydrogen ions inside the glass (from the internal buffer solution) is different from that in the sample solution outside, a tiny electrical potential (voltage) is created across the glass membrane. The magnitude of this voltage changes with the pH of the sample.
   4. Comparison and Display: The meter measures the difference in voltage between the measuring electrode (which has a variable potential) and the stable reference electrode. The meter then uses this voltage difference to calculate and display the corresponding pH value on its screen. A higher voltage indicates more hydrogen ions (lower pH/more acidic), and a lower voltage indicates fewer hydrogen ions (higher pH/more alkaline).

How ORP meters Work

• Positive ORP values indicate an oxidizing environment, which is typically associated with a higher presence of disinfectants like oxygen or chlorine and generally healthier water in applications like swimming pools.
• Negative ORP values indicate a reducing environment, which means the solution is more likely to donate electrons and may contain contaminants or decaying matter. 

Key Features to Consider when choosing a meter

• Automatic Temperature Compensation (ATC): This feature automatically corrects pH/ORP readings for temperature variations, which is important because temperature affects the pH/ORP of a solution.
• Replaceable Probes: Higher-end models often allow for the replacement of the probe (electrode) when it wears out, which saves money long-term as you don't need to replace the entire unit.
• Accuracy: Consider the required precision; laboratory and industrial applications may need a very precise reading, while domestic, agricultural use might require less precise readings.
• Application-Specific Probes: Specialized probes exist for measuring various substances which have different requirements than liquid testing.
• Calibration: Meters need regular calibration with buffer solutions of known pH/ORP values to maintain accuracy. 

Pocket/Pen pH Testers

pH02	JC610N	pH51	pH54	pH55	AK90
pH56	JC630	JC650N	JC628N	pH58

Portable pH Meters

Bench pH Meters

MW150	JC6175KA	AK130	MW151	AK131	JC6177M	JC6179M	MW160