Measuring method of conductivity meter

Measurement method of conductivity meter Measurement method of laboratory conductivity meter There are DC measurement method and AC measurement method for measurement of conductance, and the latter is mainly used. Currently, the sensor used in AC conductance measurement method mainly has two electrodes and four. electrode.

The principle of two-electrode measurement is shown in Figure 1. During the measurement of conductivity, a constant amplitude voltage signal is applied between the two electrodes, and a certain current Ix flows through the electrode. The magnitude of the current depends on the amount of ions contained in the solution, and the ion. The charge number and mobility, the conductivity of the measured medium is proportional to the output voltage of the op amp. In fact, this measurement method measures low resistance (<1kΩ). If the frequency of the AC measurement signal used is too low, the polarization effect will occur because the measurement power supply contains a certain DC component.

Therefore, for low resistance or high conductivity measurement, a higher measurement frequency should be adopted, so that the oxidation and reduction reactions on the electrode surface are rapidly alternated to reduce or eliminate the error caused by the polarization effect on the conductance measurement. When measuring low conductivity or high resistance, the frequency of the measured AC signal cannot be too high due to the influence of the capacitance of the conductivity cell, otherwise the capacitive reactance will bring a large error to the measurement.

Generally, the signal source frequency of the two-electrode AC conductance measurement is 1 kHz to 3 kHz, and the low frequency is 50 Hz to 150 Hz. In this two-electrode technique measurement, the electrode is both a current electrode and a voltage electrode. In fact, as long as a current flows through the electrode, a polarization voltage is generated on the contact surface between the solution and the electrode, causing a certain error in the measurement. The main measure to eliminate the effects of polarization voltage is to make the current as small as possible, close to zero. The four-electrode technology is designed using this argument.

The principle of the four-electrode measurement is shown in Figure 2, where b and b' are current electrodes, a and a' are voltage electrodes, and G is a sine wave signal voltage generator. Since the input impedance of the integrated operational amplifier A is sufficiently high, the current flowing through the voltage electrodes a, a' is approximately zero, so that the polarization voltage is not generated on the measuring electrodes a, a', thereby eliminating the polarization voltage. The impact on the measurement.




Guangzhou Chengmin Electronic Technology Co., Ltd. professional advantage agent sales Japan Yokogawa YOKOGAWA full range of measurement and test instruments, analytical instruments:

SC450G four-wire conductivity meter / resistivity meter






The new SC450G four-wire conductivity meter/resistivity meter has a touch screen with strong functionality and reliable performance. It is widely used in water quality measurement of drinking water, solution measurement in manufacturing process, and resistivity measurement of pure water and ultrapure water in semiconductor, food, pharmaceutical, electric power and other industries.

The SC450G's unique human-machine interface displays process, analysis, trend and log data and is available in eight languages. User-friendly, staged calibration operations help improve quality.

The SC450G also enables pure water monitoring in accordance with USP standards, making it ideal for applications in the pharmaceutical industry. HART communication of the output current signal can also be achieved.

DC402G double cell conductivity meter






Flexibility, reliability and low maintenance are the most outstanding advantages of the DC402G dual-cell conductivity meter.

Designed to meet the demanding dual cell conductivity measurement requirements of modern industrial environments, its diverse performance guarantees the highest accuracy regardless of application. Signals such as differentiation, ratio, offset, percentage of circulation, percent inhibition, etc. can be indicated or varied.
FLXA21 modular two-wire conductivity meter


The FLXA21 is a new generation of modular liquid analyzers that can be flexibly configured to measure pH/ORP, contact conductivity, inductive conductivity or dissolved oxygen. The FLXA21 can be connected to two sensors of the same model at the same time, thus reducing installation costs and saving space for a highly reliable dual sensor measurement system.

The FLXA21 features advanced and reliable features and functions such as touch screen for improved operability, sensor self-diagnostics, maintenance time estimation, and display options in 7 languages.

SC202G, SC202S two-wire conductivity meter / resistivity meter (general type / explosion-proof type) [discontinued, completely replaced by SC450G]






Designed for two-wire system configuration, the SC202 is ideal for large instrumentation systems. It can be used in hazardous areas and digital communication can be achieved using HART, Profibus-PA or fieldbus protocols.

Suitable for water quality measurement in water treatment plants and drinking water systems, cleaning of various process solutions and metal surface treatment processes, conductivity measurement of plating solutions, pure water and ultrapure water in the semiconductor, food, pharmaceutical and power industries Resistivity measurement. The SC202 can also achieve pure water monitoring in accordance with USP standards.

SC72 portable conductivity meter






The SC72 portable conductivity meter is small, lightweight and has a waterproof and robust structure. The large screen is easy to read LCD display, 300 points data storage, self-diagnosis function and automatic shutdown.

ISC202G, ISC202S two-wire inductive conductivity meter / resistivity meter (general / explosion-proof type) [discontinued, completely replaced by ISC450G]






The ISC40 non-contact inductive conductivity sensor is resistant to contamination and corrosion. Supports digital communications using HART, Profibus-PA or fieldbus protocols.

Suitable for concentration control in the chemical industry, conductivity measurement in food, pharmaceutical, electroplating and metal surface treatment, paper and other industries. The meter has a wide measuring range with zero point suppression, concentration readings and a variety of other convenient functions.

SC210G Conductivity Sensor






The SC210G conductivity sensor is widely used in a variety of water treatment and manufacturing process applications. Available in a variety of mounting styles, threaded, flange mounted, flow-through and threaded with gated valves.

SC8SG Conductivity Sensor






SC8SG is used in a wide range of applications, such as liquid conductivity measurement in manufacturing processes, and pure water resistivity measurements in the semiconductor, food, pharmaceutical, and power industries. There are a wide range of mounting types, threaded, flow-through with Screw fittings and flow-through with flanges.

SC4AJ Conductivity Sensor






The SC4AJ conductivity sensor is easy to operate, small and lightweight, and is widely used in boiler water and hydroponic cultivation conductivity measurement, as well as in pure water resistivity measurement in the semiconductor, food, pharmaceutical and power industries.

ISC40GJ, ISC40S Inductive Conductivity Sensor (General / Explosion Proof)




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The ISC40 has a wide measuring range (1μS/cm~1999mS/cm), accurate measurement, and a wide range of process temperatures (-10~130°C). The sensor wetted parts are coated with PEEK high performance engineering plastics for safe use in contaminated, abrasive or contaminated liquid applications.
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