Sensor Information


The key component to making your automatic chemical controller work to its highest efficiency is good, fast-responding, highly accurate sensors. Our sensors for both ORP (sanitizer) and pH (acid or base) are high resolution, non-corrosive sealed electrodes. For accurate measurement and control, Chemtrol Sensors utilize a platinum band on their ORP sensors and a glass top on the pH sensors. Both come with a standard 10' coaxial cable with BNC connectors and a one-year manufacturer limited warranty.

CAT sensors are heavy duty ABS body with poly-pro reference. They have a porous Teflon junction fast response with a stable signal. Ultra high resolution measurement and control with standard 24" coaxial cable and BNC connectors. CAT sensors have a two-year manufacturer limited warranty.

Keep your chemical automation working the way it should by regular preventative maintenance, cleaning, and scheduled replacement.

The pH sensor samples water from the filtration system and send signals to the controller indicating the acidity of the water. The ideal pH range for pools and spas is 7.4 - 7.6. Most pools run best at 7.5 pH. If pH is maintained below 7.4 (too acidic), eye irritation, corrosion of equipment, and damage to the pool or spa surface can occur. If pH is maintained above 7.6 (too alkaline), sanitizer activity is reduced, water may become cloudy, and eye irritation may result. For an example, see the Chemtrol 122 pH Sensor for more information.

The ORP sensor samples water from the filtration system and sends signals to the controller indicating the oxidation-reduction potential (redox) of the water. ORP is an actual measure of the sanitizer activity (chlorine, bromine, ozone, etc.) and bacteriological water quality rather than an expression of chemical residual levels. The minimum standard is 650mv set by health departments. For more information, view the Chemtrol 123 ORP Sensor.

The sensors must be clean and free from oil, chemical deposits, and contamination to function properly. After saturation in pool or spa water, the sensors may need to be cleaned on a weekly or monthly basis depending on bather load and other facility-specific characteristics. Slow response, increased need to calibrate pH, and inconsistent readings are indications that the sensors are in need of cleaning.

To clean the sensors, disconnect from the controller and carefully remove them from the flow cell. Clean the reference junction (the white Teflon ring at the bottom of sensor body) with a soft toothbrush and regular tooth paste. A household liquid dishwashing detergent may also be used to remove any oil. Rinse with fresh water, replace Teflon thread-seal tape, and reinstall sensors. Hand tighten only. Never allow a pH or ORP sensor to dry completely. Drying will damage the reference junction and void the sensor warranty.

pH and ORP sensors are engineered to provide the highest performance and longest possible functional service life. If properly cleaned sensors provide unstable readings or require excessive calibration, the pair of sensors should be replaced. For optimum controller performance, it is recommended to replace with the original manufacturers sensors. If properly maintained, normal life expectancy is 2-3 years, although many operators replace annually.

Exposure to atmospheric conditions will cause the sensor tips to dry out. If sensors are to be removed or stored for one hour or longer, always remove and properly store sensors in the soaking caps provided. Although CAT Professional Series sensors are freeze-resistant, they must be protected from freezing temperatures when not in use. Store sensors in the soaking caps provided, making sure that each container is filled with the original storage solution or clean water. If the storage containers have been misplaced, store sensors individually in small glass or plastic containers with clean water covering sensor tips. Sensors should be prepared for storage as outlined above and protected from freezing temperatures. Winter storage in a secure location is desirable.

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