Introduction: Conductivity is the ability of an object to conduct electrical current. The measurement principle of a conductivity meter is to place two parallel plates into the solution being measured, apply a certain potential (usually a sine wave voltage) to both ends of the plates, and then measure the current flowing between the plates.
　　
According to Ohm's Law, the reciprocal of conductivity (G) and resistance (R) is determined by the conductor itself. The basic unit of conductivity is Siemens (S), formerly known as Ohm. Because the geometric shape of the conductivity cell affects the conductivity value, standard measurements are expressed in units of conductivity S/cm to compensate for differences caused by various electrode sizes. Unit conductivity (C) is simply the product of the measured conductivity (G) and the conductivity cell constant (L/A) Here, L is the length of the liquid column between the two plates, and A is the area of the plates.
　　
aqueous solutionconductivityDirectly proportional to the concentration of dissolved solids, and the higher the concentration of solids, the greater the conductivity. The relationship between conductivity and dissolved solid concentration is approximately expressed as: 1.4 μ S/cm=1ppm or 2 μ S/cm=1ppm (per million units of CaCO3). The total hardness value of water can be indirectly obtained using a conductivity meter or a total solid solubility meter. As mentioned earlier, for the convenience of approximate conversion, 1 μ s/cm conductivity=0.5ppm hardness. Conductivity is the ability of a substance to transmit electrical current, relative to its resistance value, measured in Siemens/cm (S/cm). The unit is expressed in μ S/cm for 10-6 and in mS/cm for 10-3. However, it should be noted that: (1) the hardness of water is indirectly measured by conductivity, with a theoretical error of about 20-30 ppm; (2) the conductivity of the solution determines the movement of molecules, and temperature affects the movement of molecules. In order to compare measurement results, the testing temperature is generally set at 20 ℃ or 25 ℃; (3) using reagents for detection can obtain relatively accurate hardness values of water.
　　
waterconductivityIt is related to the amount of inorganic acids, bases, and salts it contains. When their concentration is low, the conductivity increases with increasing concentration, therefore, this indicator is commonly used to infer the total concentration or salt content of ions in water. Different types of water have different electrical conductivities. The conductivity of fresh distilled water is 0.2-2 μ S/cm, but after being left for a period of time, it increases to 2-4 μ S/cm due to the absorption of CO2; The conductivity of ultrapure water is less than 0.10/μ S/cm; The conductivity of natural water is mostly between 50-500 μ S/cm, while mineralized water can reach 500-1000 μ S/cm; The conductivity of industrial wastewater containing acid, alkali, and salt often exceeds 10000 μ S/cm; The conductivity of seawater is about 30000 μ S/cm.
　　
The electrode constant is often measured using a standard potassium chloride solution with known conductivity. The conductivity (25 ℃) of potassium chloride solutions with different concentrations is listed in the table below. The conductivity of a solution is related to factors such as temperature, polarization phenomenon on the electrode, and electrode distribution capacitance. Compensation or elimination measures are generally adopted in instruments.
　　
The characteristics of a conductivity meter mainly include:
　　
◆ One click button automatic calibration:
　　
The instrument can be automatically calibrated at one point per range with standard conductivity solution. During calibration, the instrument automatically recognizes the calibration solution. If you use the wrong or significantly deviated conductivity solution for calibration, the instrument will automatically sound an alarm.
　　
◆ Automatic range conversion: When measuring conductivity or total dissolved solids (TDS), the instrument has an automatic range conversion function. After the electrode sensor is immersed in the solution, the BEC portable model will automatically scan the current measurement value and convert the range, and the instrument will display the endpoint measurement value with a resolution of.
　　
◆ Temperature coefficient can be set:
　　
Solutions containing different ions often have different temperature coefficients, and accurately setting the temperature coefficient is crucial for measurement. The BEC portable model can be set within the range of 0 to 3.9% per degree Celsius.
　　
◆ electrode constant can be set:
　　
When measuring high or low conductivity solutions, you need to choose conductivity electrodes with different constants. The BEC portable model has three electrode constants to choose from, and you can set them according to the selected electrode. The instrument will automatically convert the endpoint measurement value.
　　
◆ TDS coefficient can be set:
　　
According to the conductivity analysis method, accurate estimation should be made when measuring the total dissolved solids in water quality. The TDS coefficient can be set between 0.01 and 1.00 for 530/540 to ensure the reliability of the measurement value.
　　
◆ Automatic message prompt:
　　
The BEC portable model has an operation information prompt function. When you enter a certain setting or measurement information bar, it will help you understand what operations the instrument can perform and how to operate it in the current state. It is equivalent to the operation steps in the user manual. Through the guidance of the information bar, you can easily complete a certain setting or measurement task.
　　
◆ Instrument configuration:
　　
One CON1 platinum conductive electrode, one temperature probe, one 9V battery, and one CON10 conductive electrode for BEC-530/531/540 configuration.