pH meters must be calibrated using how many buffers?

To ensure accurate readings, pH meters are typically calibrated using two buffers. This process helps establish a linear relationship between the voltage measured by the pH meter and the corresponding pH values. Utilizing two buffers, usually one at a low pH (such as pH 4.00) and one at a high pH (such as pH 7.00 or pH 10.00), allows for the meter to accurately interpolate values between these two points.

Calibrating with two buffers is especially important because pH meters are not perfectly linear across all values. The calibration with two distinct points creates a more reliable and precise pH measurement across the range of expected values. Using only one buffer would not provide enough information for the meter to correctly interpret readings in the entire pH scale, and using more than two buffers, while still sometimes utilized in high-precision applications, is generally not required for standard operations.