First, check the following box inspection device after the instrument out of the box: ● PHS-3C pH meter 1 set ● 1 ● Short circuit composite electrode plugs (already inserted in the back of the instrument electrode socket) 1 ● electrode holder and electrode holder ( metal bending type) 1 set ● Temperature sensor (pHS-3DW designed with) a ● 1 ● Power Adapter standard buffer reagent: pH4.00, pH6.86, pH9.18 1 set ● 1 ● Product Manual warranty card 1 ● product certification a job conditions ● Ambient temperature: 0 ~ 40 ℃ Relative humidity: <85% ● Power supply: 9V DC power supply ● ● no significant vibration outside Earth's magnetic field in addition to no external magnetic interference ● Input Impedance: ≥1 × 1012Ω ● Zero drift: ≤0.01pH ± 1 word / 2 hours ● solution temperature compensation range: 5 ~ 60 ℃ ● Dimensions and weight: 230 × 200 × 60mm (length × width × height) 1.2Kg Second, the instrument to measure the general principle of pH measurement with a glass electrode pH value of an aqueous solution of the basic principles as the electrode, calomel electrode as the reference electrode instructions, when the hydrogen ion concentration of the solution (Strictly speaking, the activity) that changes the pH of the solution When the potential to produce between the glass electrode and calomel electrode, along with the change, and potential changes in the relationship conforms to the following formula: △ E = -58.16 × △ pH × (273 + t ℃) / 293 (mV) △ E: indicate potential changes in millivolts. (MV) △ pH: shows the change in pH value. t: indicates the temperature of the test solution (℃). Commonly used indicator electrode glass electrodes, antimony electrodes, fluorine electrode, a silver electrode and so on, where the most widely used glass electrode. pH glass electrode head is made of special sensitive film, it has a sensitive role of hydrogen ions when it is inserted in the test solution, and its potential with the measured liquid hydrogen ion concentration and temperature. In the solution temperature is 25 ℃, every change in a pH, electrode potential to change 59.16mV. This is the theoretical slope coefficient often said electrodes. Commonly used as a reference electrode calomel electrode, its potential is not with the measured liquid hydrogen ion concentration change. essence pH measurement is to measure the potential difference between the two electrodes. When the potential of the pair of electrodes of the difference is equal to zero in the solution, pH value of the measured solution pH value, i.e. zero potential, it is concerned with the solution of a glass electrode. The instrument is equipped with a composite electrode made of glass electrode and Ag-Agcl integrated electrodes, the pH value of the zero position at 7 ± 0.25pH. Circuit processing circuit block diagram of the instrument as shown: Since the glass electrode internal resistance is high, about 2 × 108Ω, therefore, the instrument is actually a high input impedance DC amplifier, impedance conversion by a high input impedance to an integrated circuit obtained. Since the pH of the solution is temperature dependent; mV-pH glass electrode slope converter is generally lower than the theoretical value, and with the increase of time of use and storage decreases; and the presence of certain discrete between the electrodes; it is necessary to have a temperature compensation apparatus and electrode slope compensation. The instrument temperature compensation and electrode pH-mV conversion slope compensation and pH positioning, calibration, etc. are automatically controlled by a microprocessor and adjustment.