pH System Installation Tips

Many people think of pH measurement as an esoteric science requiring long years of apprenticeship to master.  With new technology and modern pH controllers, this is no longer the case. With a little care and patience everyone can successfully install and operate today’s advanced pH controllers. The following guidelines, used with the manufacturer’s instructions, should assure you a trouble-free pH system installation.

Controller Wiring

pH instruments are designed to accurate measure an extremely small (millivolt level) electrical potential in the fluid. This ability makes them sensitive to stray electrical signals in their immediate environment. pH instruments should be isolated from high voltage electrical panels, motors and pumps.  The pH units should have a ‘clean’ power source not attached to motors or pumps.  When connecting large pumps or actuated valves to the units, power should be run through external relays, not directly to the pH unit.

Sensor Installation

pH sensors should be mounted within 45 degrees of vertical to assure proper operation.  Sensor cable should not be coiled or run near AC power lines.  When using a preamp in a submerged application, you must ensure that the seal between the sensor and preamp is watertight to prevent fluid leakage from damaging the preamp.

Sensor Care

The most critical component of your pH system is the sensing electrode.  pH sensors work by inducing a slight electrical voltage potential into the solution and then measuring the voltage (mv) carried by free hydrogen ions (H+) in solution.  This voltage will vary with the pH level.  In reality, the pH sensor acts as a battery, and like all batteries it eventually wears out.  The lifespan of your sensor is a function of many variables.  As a general rule, the higher your temperature, and the further your pH deviates from neutral (pH 7), the shorter the effective lifespan of your probe.  Sensor condition can be checked by reading the mv display with the sensor in a pH #7 buffer solution.  Ideally, this reading would be close to zero.  As the sensor ages, the deviation will increase.  Once the deviate reaches +/- 45 mv or more, the sensor should be replaced.  The pH sensor should be kept wet at all times and stored in an upright position when possible.

Calibration

pH units must be calibrated to perform accurately. This includes calibration of temperature, standardizing at pH #7 and sloping at pH #4 or #10.  pH sensors will ‘drift’ as they age and this calibration should be repeated periodically to assure accurate measurement.  RHFS can provide buffer solutions for calibrating your pH systems.

pH system installation isn’t difficult if these basic tips are kept in mind.  If you have specific questions or concerns about an application, please contact the RHFS TechTeam by clicking or calling 877-741-7437 for support and assistance.