Oxidation-Reduction Potential (ORP) is a measure of the redox potential of a solution, expressed in millivolts (mV). This ORP meter is a specialized instrument designed to test the redox potential of liquids. The device features a waterproof enclosure with an IP55 rating and a replaceable electrode. It includes a data hold function for convenient measurement reading and recording. Incorporating advanced technology and components, this compact ORP tester offers reliable performance in a smaller, cost-effective design. It is suitable for use with water purification systems and other applications requiring measurement of negative potential. Main technical specifications: - Measurement range: 0 to ±1999 mV - Resolution: 1 mV - Accuracy: ±5 mV - Battery: 4 x 1.5V (AA) – not included - Operating temperature: 0 to 50°C - Calibration: 1-point calibration Instructions: 1. Remove the protective cover. 2. Press the "ON/OFF" button to power on the device. 3. Immerse the electrode into the test solution and gently shake until the reading stabilizes. 4. Press the "HOLD" button to lock the current reading. To resume measurement, press "HOLD" again to release the hold function. 5. After use, turn off the device, rinse the electrode with distilled water, and replace the protective cover. Battery replacement: If the display appears dim or unclear, replace the batteries. Open the battery compartment, insert new batteries according to the correct polarity, and secure the cover. Calibration procedure: 1. Soak the electrode in distilled water for several hours before calibration. 2. Immerse the electrode in the calibration solution and stir gently. 3. Use a screwdriver to adjust the calibration trimmer until the display reads 265 mV. 4. Rinse the electrode with distilled water and blot dry with a soft tissue. Color: White + Green Material: ABS + electronic components Dimensions: 18.8 cm x 3.5 cm x 3.5 cm Package contents: 1 x 169E ORP Tester 1 x English manual Note: Light and screen display differences may cause slight variations in the color shown in images. Measurement error is ±1–3 cm.