Open box inspection

Please check the following components after unboxing the instrument:
1. One portable pH meter host
2. Composite electrode 018 Temperature electrode 1 piece
3. Short circuit plug (already plugged into the electrode socket on the back of the instrument) 1
4 DC1.5V batteries with size 4.7
5. Standard buffer reagents: pH4, pH6.86, pH9.18 1 set
6. One user manual
7. One product warranty card
8. One copy of product qualification certificate
2、 Technical characteristics and usage conditions of the instrument

Measurement range: pH：0～14.00pH; mV:±1600mV，
Temperature: 0-60 ℃
resolving power: pH：0.01pH，
Temperature: ± 1 ℃
Accuracy: pH：0.01pH， Temperature: ± 1 ℃
Temperature compensation: 0-60 ℃ automatic temperature compensation/manual compensation
Basic configuration: E201-C plastic shell PH composite electrode; PH standard calibration sample; 4 DC1.5V batteries, No.7

working conditions
● Environmental temperature: 0-40 ℃ Relative humidity: ＜ 85％
Power supply: 1.5V battery/4 cells
● No significant vibration
● No external magnetic field interference except for the Earth's magnetic field
● Input impedance:& ge;1*1012Ω
● Zero drift: ≤ 0.01pH ± 1 word/2 hours
Solution temperature compensation range: 0-60 ℃
● Dimensions and weight: 180 * 80 * 30mm (length * width * height) 0.5Kg
● Power consumption: 2 W

3、 Instrument working principle
Basic principles of pH measurement
The measurement of pH value in aqueous solution generally uses a glass electrode as the indicator electrode and a calomel electrode as the reference electrode. When the concentration (strictly speaking, activity) of hydrogen ions in the solution, that is, the pH value of the solution, changes, the potential generated between the glass electrode and the calomel electrode also changes, and the potential change relationship follows the following formula:
△E ＝ －58.16*△pH*(273+t℃)/293（mV）
△ E: represents the change in electric potential, measured in millivolts. （mV）
△ pH: represents the change in pH value of the solution.
t ： Indicate the temperature of the tested solution (℃).
The commonly used indicator electrodes include glass electrodes, antimony electrodes, fluorine electrodes, silver electrodes, etc. Among them, glass electrodes are the most widely used. The pH glass electrode head is made of a special sensitive film, which has a sensitive effect on hydrogen ions. When it is inserted into the measured solution, its potential changes with the concentration and temperature of hydrogen ions in the measured solution. At a solution temperature of 25 ℃, for every pH change, the electrode potential changes by 59.16mV. This is commonly known as the theoretical slope coefficient of electrodes.
The commonly used reference electrode is the calomel electrode, whose potential does not change with the concentration of hydrogen ions in the measured liquid.
The essence of pH measurement is to measure the potential difference between two electrodes. When the potential difference generated by a pair of electrodes in a solution is equal to zero, the pH value of the measured solution is the zero potential pH value, which is related to the solution inside the glass electrode. This instrument is equipped with a composite electrode consisting of a glass electrode and an Ag Agcl electrode, with a zero point pH value of 7 ± 0.25pH.

4、 Instrument usage method
prepare
Open the battery cover behind the instrument and install 4 1.5V batteries (pay attention to the positive and negative stages). Remove the short-circuit plug from the electrode socket of the instrument and insert the electrode. Pay attention to keeping the electrode plug clean and dry before use, and avoid contamination.
Turn on the power and press the power button to preheat for about 5 minutes.
Calibration of instruments
Special reminder: This instrument must be calibrated using three standard buffer solutions: 4.00, 6.86, and 9.18
Before pH measurement, the instrument needs to be calibrated first. To obtain accurate measurement results, the standard buffer solution used during calibration should ensure accuracy and reliability.
Connect the power and press the (switch) button to turn on the device.
Unscrew the short-circuit protection cover on the pH socket, connect the plastic shell pH composite electrode, wash the electrode in pure water and shake dry.
Measure the temperature of the pH buffer solution with a thermometer, and adjust the temperature value displayed on the LCD screen accurately by pressing the increase button (&nd;) or decrease button (∨).
Positioning calibration: Immerse the pH electrode in a pH 6.86 buffer solution, stir it slightly, and let it stand still. After the measurement value stabilizes, hold down the (calibration) button. When the LCD screen displays the CAL symbol, release it. First, the flashing 6.86 symbol will be displayed. After a few seconds, the End symbol will be displayed, and then the pH calibration value will be displayed (the pH value displayed at this time varies with temperature, for example, 6.86 at 25 ℃ and 7.04 at 15 ℃ are the values set by the chip, the same below). Indicates completion of calibration and memorization.
Slope calibration I: Take out the pH electrode, wash it with pure water and shake it dry. Then immerse the pH electrode in a pH 4.00 buffer solution, stir it slightly, and let it stand still. After the measurement value stabilizes, hold down the (calibration) button and release it when the CAL symbol is displayed on the LCD screen. First, the flashing 4.00 symbol will be displayed. After a few seconds, the End symbol will be displayed, and then the pH calibration value will be displayed, indicating that the calibration is completed and memorized. After calibration, the slope percentage of the electrode in the linear segment will be automatically displayed.
Slope Calibration II: Take out the pH electrode, wash it with pure water and shake it dry. Then immerse the pH electrode in pH 9.18 buffer solution, stir it slightly, and let it stand still. After the measurement value stabilizes, hold down the (calibration) button and release it when the CAL symbol is displayed on the LCD screen. The flashing 9.18 will be displayed first, followed by the End symbol after a few seconds, and then the pH calibration value will be displayed, indicating that the calibration is completed and memorized.
Solution measurement
Measure the temperature of the solution with a thermometer (including automatic temperature detection by temperature electrodes), and then press the add button&nd; Or decrease key∨ Adjust the temperature value of the instrument accurately, wash the pH electrode, immerse it in the measured solution, stir it slightly, and let it stand still. When the measured value stabilizes, read the value, which is the measured pH.

pay attention to
According to the principle of pH isothermal measurement, the closer the temperature of the measured solution is to the temperature of the calibration solution, the higher the accuracy of the measurement. It should be observed during actual testing.

describe
This instrument is equipped with an intelligent chip that can automatically calibrate at any point, two or three. If the measurement accuracy is ≤ 0.1pH, a pH buffer solution can be used for one point calibration; If the measurement range is only within the acidic range (≤ 7pH), pH 7 and pH 4 calibration can be selected; If the measurement range is only within the alkaline range (7pH), pH 7 and pH 10 calibration can be selected; If the measurement range is wide or the pH electrode has aged for a long time, three-point calibration should be selected to improve measurement accuracy. The pH electrode used for the first time must undergo three-point calibration to adjust the slope of the instrument to be consistent with the pH electrode.
Note: The PHB-4 pH meter is equipped with E201-C-W plastic shell pH triple composite electrode or 018 temperature electrode, and the instrument can perform pH testing with automatic temperature compensation.
Test mV value:
Press the (pH/mV) button to switch the instrument to the (mV) range,
Connect the ORP electrode or ion electrode (to be equipped separately) and insert it into the solution to be tested. Stir it slightly and let it stand still. After the measured value stabilizes, read the ORP value or the potential value of the ion electrode.

5. Maintenance and usage precautions for instruments
The quality of an instrument is inseparable from proper maintenance, standardized operation, and correct methods, in addition to the structure of the instrument itself.
Precautions for measuring samples
The electrode plugs and sockets of the instrument must be kept clean and dry. When not in use, short-circuit plugs or electrode plugs should be plugged in to prevent dust and moisture from entering and reducing the input impedance of the instrument, which may affect the accuracy of the measurement.
Suitable pH electrodes should be selected for different samples (such as measuring strong acids, strong bases, or pure water).
During sample measurement, the lead wire of the electrode must remain stationary and should not be touched by hand. Otherwise, it will cause measurement instability.
Secondary distilled water or deionized water must be used to prepare the standard solution, and its conductivity should be less than 2uS/cm, preferably boiled for use.
To ensure the accuracy and reliability of the standard buffer solution, the alkaline solution should be sealed tightly in a polyethylene bottle. Standard buffer solution should be stored in a refrigerator (at a low temperature of 5-10 ℃) and can generally be stored for 2-3 months. If turbidity, mold, or sediment is found, it cannot be continued to be used.
Do not use standard buffer solutions that have exceeded their shelf life, and do not pour used standard buffer solutions back into the standard solution storage bottle.
When calibrating, use a standard buffer solution as close as possible to the pH value of the sample, and the temperature of the calibration solution should be as consistent as possible with the temperature of the sample.
If the electrode is replaced during the use of the instrument, it is best to turn it off and then turn it on again to recalibrate.

Precautions for electrode use
Composite electrodes should not be immersed in distilled water for a long time. When not in use, the electrode should be inserted into a bottle containing electrode protection solution to keep the electrode bubbles in an active state.
Preparation of electrode protection solution: Take a bag of pH 4.00 buffer (250ml) and dissolve it in 250ml of ionized water. Then add 56g of analytical grade Kcl and stir until completely dissolved.
After removing the electrode protective cover, the electrode head should be avoided from collision to prevent the glass bulb of the electrode from breaking and causing the electrode to fail.
When using a liquid filled electrode, attention should be paid to whether the reference liquid inside the electrode has decreased. If it is less than 1/2 of the volume, a dropper can be used to add it from the small hole at the top. When measuring, the sealing sleeve should be moved downwards to expose the small hole.
Before transferring the electrode from one solution to another, clean the electrode with distilled water and dry the water with filter paper. Do not deliberately wipe the glass bulb of the electrode, otherwise it may cause slow electrode response. The best method is to rinse the electrode with the tested liquid.
Avoid the presence of bubbles in the reference solution inside the electrode. If there are bubbles, shake the electrode to eliminate them.
The response time of instrument readings is related to the internal resistance of the electrode, the temperature of the solution, and the properties of the solution, especially when measuring solutions with low dissociation degree (such as pure water), as well as when the solution temperature is low or the electrode is aging, the stability time of instrument readings will be relatively long.
When testing strong acids, strong alkalis, or special solutions (such as solutions containing proteins, paints, etc.), the soaking time should be minimized as much as possible and carefully cleaned after use. The best method is to choose an E314 composite electrode.
After long-term use, the slope and response speed of the electrode will decrease. The electrode bulb can be soaked in a 0.1mol/L dilute HCl solution (preparation: 9ml HCl diluted to 100ml with ionized water) for 24 hours. If passivation is severe, the electrode bulb can be soaked in a 4% HF solution (preparation: 4ml HF diluted to 100ml with ionized water) for 3-5 seconds, cleaned with distilled water, and soaked in an electrode protection solution to allow for proper recovery. If neither method can restore it, please replace the electrode.
When the sample solution contains substances that can easily contaminate sensitive bubbles or block the liquid interface of the reference electrode (such as suspended solids, emulsions, viscous liquids, etc.), it can passivate the electrode. The phenomenon is a decrease in sensitivity, or unstable and inaccurate reading drift. In this way, according to the nature of the pollutant, it should be cleaned with an appropriate solution, then distilled water should be used to remove the solvent, and soaked in electrode protection solution to restore it.
Cleaning methods for pollutants: (for reference)
Pollutant cleaning agent
Dilute acid with inorganic metal oxide concentration below 1mol/L
Organic oil-based weak alkaline detergent
Resin polymer substances such as alcohol, acetone, ether, etc
Protein hemocyte sediment acidic enzyme solution (such as maternal tablets)
Pigments such as dilute bleach, hydrogen peroxide, etc
★ Attention: When selecting cleaning agents, if using cleaning solutions that dissolve polycarbonate resin, such as carbon tetrachloride, trichloroethylene, tetrahydrofuran, etc., it may dissolve the polycarbonate resin (electrode material) and apply it to sensitive glass bubbles, causing electrode failure. Please use with caution!
Inspection and judgment of general faults
Most measurement problems arise from electrode malfunctions or measurement method errors, rather than the instrument itself. In addition, the use of standard buffer solution, samples, and many other factors can also lead to problems. Please analyze carefully to determine the root cause of the problem.
● Electrode
If the instrument host is judged to be normal, but when tested with electrodes, the displayed value is unstable or the instrument response is slow; Poor reproducibility; Or if the required pH value cannot be calibrated, please check the electrode:
Whether the connection is good, and whether the two ends of the electrode leads are loose or disconnected;
Is the electrode bubble immersed in the sample;
Whether there are bubbles in the solution inside the electrode;
Is the electrode bubble contaminated;
If the above situation occurs, please replace the electrode with a new one.
● Standard buffer solution
If both the host and electrodes are normal, but the readings are incorrect or cannot be calibrated, please check the buffer solution:
Is the correct pH standard buffer used;
Check if the buffer has exceeded its shelf life or has been contaminated or inaccurate;
If so, prepare a pH standard buffer solution again.
6. Preparation of standard buffer solution
Pour the standard buffer reagent provided with the instrument into a 250ml volumetric flask, rinse the plastic bag with distilled water (preferably boiled), dissolve and dilute to the mark, shake well and set aside.
Comparison table of pH value and temperature relationship of commonly used standard buffer solutions: