Open the battery cover of the instrument and load the batteries correctly. Before using the instrument, if you have replaced the probe electrode, you should calibrate it before measuring the pH value of the solution. It is not always necessary to calibrate the electrode before use, but generally once a month if the measurement interval is short.The instrument is calibrated in a three-point mode. In the normal measurement state, press and hold the "CAL/▲" key for 3 seconds to enter the following mode:

1. The LCD first shows CAL 1 blinking and 4.00 constant light, clean the probe with distilled water, put the probe into PH4.0 solution, when the internal judgment of the sensor signal is stable, the LCD shows the prompt of PAS, indicating the success of CAL1 calibration, and automatically turn to the next calibration point CAL2 blinking and 6.86 constant light.

2. After a quick cleaning of the probe, the probe is inserted into the 6.86 PH solution and when the signal from the sensor is judged to be stable internally, the LCD displays a PAS prompt indicating a successful CAL2 calibration and automatically moves to the next calibration point CAL3 flashing state and 9.18 constant light.

3. After a quick cleaning of the probe, the probe is inserted into the 9.18 PH solution and when the signal from the sensor is judged to be stable internally, the LCD displays a PAS indication that all calibration points have been successfully calibrated and automatically switches to normal test mode.

4. If the calibration solution used is not the preset value, press CAL/▲ or /▼ during calibration to adjust the value to the value of the calibration solution and then calibrate.

5.If the LCD shows Err during calibration, the calibration point has failed, the calibration solution is not within the range of the calibration point or the sensor has failed.

6. Normal measurement mode: The power is switched on in normal measurement mode by default. The normal measurement mode measures the PH value and displays the ambient temperature value. In measurement mode the pH value is displayed by placing the electrode in the solution to be tested.

7. When the battery symbol is displayed in the upper right corner of the display, replace the battery. Remove the batteries when the instrument is not in use for a long period of time.

8. ON/OFF/HOLD key: short press to switch on, short press to lock the current measured reading after switching on, long press to switch off.

9. CAL/▲ keys.a. In the normal measurement state, press and hold for 3 seconds to enter CAL calibration mode.b. In calibration mode, short press to add a value, short press to increase the value and long press to increase the value quickly among the 3 calibration values in CAL state.

10. /▼ keysa. Press briefly to turn the backlight on or off.b. In calibration mode, short press to reduce the value, short press to reduce the value and long press to quickly reduce the value among the 3 calibration values in CAL status.

11. Auto power off setting: Press and hold the ON/OFF key and CAL/▲ key at the same time before power on to enter the auto power off setting mode, the LCD screen will display the APO ON or APO OFF selection interface, short press the ON/OFF key to select between APO ON and APO OFF. Press and hold the ON/OFF key to save and exit this mode.a. APO ON mode: The screen displays the timer symbol and switches off automatically after 15 minutes without any key operation.b. APO OFF mode: The power will not be switched off automatically, it needs to be switched off manually and the screen will not display the timer symbol.12. Temperature unit conversion mode: Before switching on, press and hold the ON/OFF key and /▼ key at the same time to enter the temperature unit conversion mode, the LCD displays the temperature in degree or degree F mode. Press the ON/OFF key briefly to change between degree and degree F modes. When the selection is complete, press and hold the ON/OFF key to save and exit this mode.13. Indication of out-of-range values in the measurement status:a. When the pH value is lower than 3. 5PH, the red backlight lights up, indicating that the liquid is close to a strong acid; when the pH value is higher than

12. 5PH, the red backlight lights up, indicating that the liquid is close to a strong base.b. When the ambient temperature is below 0 degree , the LCD temperature value displays LO, when the ambient temperature is above 70 degree , the LCD temperature value displays HI.

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