Feature: 1.Often troubled by calibration problem? Just one touch button can help you calibrate the digital tester. Dissolved oxygen meter is equipped with 0% and 100% 2‑point automatic calibration buttons, convenient for calibration. 2.Have you ever seen a digital test pen designed with premium accuracy together with fast response? With automatic temperature compensation function ,dissolved oxygen test pen can solve possible inaccuracy caused by the change of liquid temperature, making more accurate. Specification: Item Type: DO Meter Material: ABS Measuring Range: Dissolved Oxygen: 0-199.9%, 0-16.5mg/L Temperature: 0℃-50℃, 32℉-122℉ Resolution: Dissolved Oxygen: 0.1%, 0.01mg/L Temperature: 0.1℃, 32.18℉ Accuracy: Dissolved Oxygen: ±1.5%F.S (Full Scale) Temperature: ±1℃, ±33.8℉ Residual Current: The reading will not return to zero when ≤0.15mg/L Response Time: ≤15 Seconds Temperature Compensation: 0℃-50℃ Power Supply: 2 x 1.5V AAA Dry Battery (Battery Not Included) Working Temperature: 0℃-50℃, 32℉-122℉ How to Use: 1. Rinse the electrode with deionized water or rinse solution. Press On/Off to turn on the machine. Immerse the electrode in the zero-oxygen solution for at least 3 minutes and keep shaking gently until the displayed value is stable. 2. Press the on/off key until the second line of the "CAL" character is displayed, and gently shake the electrode. When the displayed value is stable, press the "%/L/mg" key, the display DO value is 0%, and the completion is zero. Calibration. Package Included: 1 x DO Meter 1 x Plastic Storage Box 3 x Sandpaper 1 x Electrode Protective Cover 1 x Manual