USER MANUAL Waterproof pH/Temperature Meter Model PH90
Introduction Thank you for selecting the Extech Model PH90 waterproof pH/Temperature meter. This instrument is equipped with a flat surface pH electrode (model pH95) for reliable test results. This device is shipped fully tested and calibrated and, with proper use, will provide years of reliable service. Please visit our website (www.extech.com) to check for the latest version of this User Guide, Product Updates, Product Registration, and Customer Support.
Description 1. Battery compartment cap 2. LCD Display 3. Power and CAL button 4. HOLD and MAX/MIN button 5. °C/°F button 6. Electrode collar 7. Electrode (PN: PH95; replaceable) 1 2 3 4 5 6 7 CAUTIONS This device contains small objects that can be swallowed; do not allow children or pets to handle or play with this device. Do not allow children or pets to handle or play with the batteries and packing material, these items pose a hazard.
Overview pH Overview pH is a unit of measure (ranging from 0 to 14pH) indicating the degree of acidity or alkalinity of a solution. Solutions with a pH lower than 7 are considered acidic, solutions with a pH higher than 7 are known as bases, and solutions with a pH of exactly 7 are considered ‘neutral’. The pH scale is logarithmic so, for example, if sample ‘A’ is 1 pH lower than Sample ‘B’, then Sample ‘A’ is 10 times more acidic than Sample B.
Operation Understanding the PH90 Display When an electrode is placed in a solution, the main display indicates the pH reading while the lower display shows temperature. pH Calibration A two point calibration with a buffer of 7 and 4 or 10 (whichever is nearest to the expected sample value) is always recommended. For best accuracy, always calibrate at the sample temperature. 1. Check that the pH icon is displayed on the LCD. 2. Dip the electrode into the pH7 buffer solution.
pH Measurements After calibration (detailed earlier), rinse the electrode with clean tap water and wipe dry. Dip the electrode into the sample solution to be measured. Stir gently and wait for a stable reading. Automatic temperature compensation is always active when measuring pH (ATC icon shown on LCD). Temperature Units Selection (oC/oF) Press and hold the C/F button to toggle the displayed temperature units of measure.
Battery Replacement 1. Unscrew the battery compartment cap counterclockwise to access the battery compartment. 2. Replace the two (2) 2032 batteries observing correct polarity. 3. Replace the battery compartment cap securely. Never dispose of used batteries or rechargeable batteries in household waste. As consumers, users are legally required to take used batteries to appropriate collection sites, the retail store where the batteries were purchased, or wherever batteries are sold.
