Introduction to the problems that should be understood before using the pH meter
A pH meter is an instrument used to measure the pH value of a solution. The pH meter works on the principle of a galvanic battery. The electromotive force between the two sensors of the galvanic battery is based on Nernst's law, which is not only related to the sensor's own properties, but also to the concentration of hydrogen ions in the solution. There is a corresponding relationship between the electromotive force of the primary battery and the concentration of hydrogen ions, and the negative logarithm of the concentration of hydrogen ions is the pH value. A pH meter is a common analytical instrument widely used in agriculture, environmental protection and industry. Soil pH is one of the important basic properties of soil. Factors such as the temperature and ionic strength of the solution to be tested should be considered in the pH determination process.
pH meter installation
①The voltage and frequency of the power supply must comply with the data specified on the nameplate of the instrument, and at the same time must be in good contact, otherwise the pointer may be unstable during measurement.
②The instrument is equipped with a glass sensor and a calomel sensor. Clamp the bakelite cap of the glass sensor on the small clip of the sensor clip, and clip the metal cap of the calomel sensor on the large clip of the sensor clip. Screws adjust the height of the two sensors.
③The glass sensor should be soaked in distilled water for more than 24 hours before the first use, and should also be soaked in distilled water when not in use.
④The calomel sensor should be soaked in a saturated solution before first use, and not soaked in distilled water together with the glass sensor. When not in use, soak it in a saturated solution or cover the lower capillary hole of the calomel sensor with a rubber cap.
Measurement
①Drain the excess water droplets on the sensor or rinse it twice with the solution to be tested, then immerse the sensor in the solution to be tested, and turn or shake the small beaker gently to make the solution contact the sensor evenly.
②The temperature of the solution to be tested should be the same as that of the standard buffer solution.
③ Adjust the zero position, press the reading switch, the value pointed by the pointer is the pH of the liquid to be tested. If the reading of the pointer exceeds the scale when measuring within the range of pH0~7, the range switch should be placed at pH7~14 Measure again.
④ After the measurement is completed, release the reading switch, and the pointer points to pH 7, otherwise re-adjust.
⑤ Turn off the power, rinse the sensor, and soak it according to the above method.
sensor use
1. The glass sensor socket should be kept dry and clean. It is strictly forbidden to contact with acid mist, salt mist and other harmful gases, and it is strictly forbidden to be stained with aqueous solution to ensure the high input impedance of the instrument.
2. When not measuring, the input should be short-circuited to avoid damage to the instrument.
3. Soak a new sensor or a sensor that has not been used for a long time in distilled water for several hours before use. The asymmetric potential of the sensor is reduced to stabilize and the internal resistance of the sensor is reduced.
4. When measuring, the sensor bulb should be completely immersed in the solution to be measured.
5. When using, the internal reference sensor should be immersed in the internal reference solution, and the internal reference solution should not be poured to the end of the sensor cap, so that the internal reference is suspended.
6. When in use, the rubber plug of the electrolyte filling port of the reference sensor should be pulled out, so that the reference electrolyte (salt bridge) can maintain a certain flow rate of penetration by gravity and communicate with the measured solution. Otherwise, readings will drift.
7. There should be no air bubbles in the * * solution, so as not to disconnect the measurement circuit.
8. The salt bridge solution should be added frequently to keep the liquid level higher than the silver/silver chloride wire.
product description
This product is an instrument independently developed by our company for online monitoring of pH value. It is output to the monitoring room for record preservation through RS485 (some models do not have this function, please refer to the selection table in the appendix for specific models) or current transmission. , continuous monitoring of pH and temperature in solution. The continuous monitoring data can be connected to the recorder through the transmission output to realize remote monitoring and recording, and can also be connected to the RS485 interface through the Modbus-RTU protocol, which can be easily connected to the computer for monitoring and recording.
Application field
Instrument controllers are widely used in thermal power, chemical fertilizer, metallurgy, environmental protection, pharmaceutical, biochemical, food and tap water industries.
Measuring principle
(1) Calibration and setting setting password protection
(2) 16X2 LCD screen with backlight display
(3) Technical parameters can be set on site with buttons
(4) High stability, high precision; can measure PH temperature
(5) Anti-interference circuit design, can be installed and used in strong interference sites after power failure, the set parameters and calibration data will not be lost, with manual setting/automatic temperature compensation process, temperature and calibration temperature, when the temperature sensor is damaged by Automatic temperature compensation can be converted into manual temperature compensation to verify test data online
(6) Multiple output modes (relay, 4.0...20.00mA. RS485)
(7) Suitable for water treatment, thermal power, metallurgy, pharmaceutical, environmental protection, food, tap water, chemical industry and other industries
