Conductivity meter is an instrument and equipment suitable for precise measurement of various liquid media, mainly used to accurately measure the conductivity value of liquid media. The product is widely used in multiple fields. What is the measurement principle of conductivity meter? Below, the editor will provide a specific introduction, hoping to help users better apply the product.
Measurement principle of conductivity meter
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. The 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. The conductivity of an aqueous solution is directly proportional to the concentration of dissolved solids, and the higher the concentration of solids, the greater the conductivity.
There are many precautions to be taken when using a conductivity meter. How to operate the conductivity meter correctly? Before turning on the power switch, observe whether the pointer points to zero. If it is not zero, adjust the screw on the meter head to make the pointer point to zero. Turn the calibration and measurement switches to the "calibration" position. Plug in the power cord, turn on the power switch, and preheat for a few minutes (until the pointer * stabilizes). Adjust the "correction" device to make the meter full indication.
When using ranges (1) to (8) to measure liquids with conductivity below 300, select "low cycle" and turn the plate towards "low cycle". When using ranges (9) to (12) to measure liquids with conductivity in the range of 300 to 300, turn it towards "high cycle". Turn the range selection switch to the desired measurement range. If the conductivity of the measured solution is unknown in advance, it should be turned to the highest conductivity measurement mode first, and then lowered step by step to prevent the needle from bending.
Generally, the knob for measuring its "constant" is turned to the 1.0 gear, and the measurement top note (ADI) is turned to the zui maximum value, and then it is slowly adjusted. The measurement switch is turned to the calibration gear to adjust the zero point, select the range, and then turn the measurement switch to the measurement position before reading. When in use, clamp the electrode cap with an electrode clamp and fix the electrode on the electrode rod through the electrode clamp.
When using a conductivity meter, it is important to note that the electrode leads should not be damp, otherwise it will affect the accuracy of the measurement. After high-purity water is poured into a container, it should be measured quickly, otherwise the conductivity will decrease quickly because the dissolved ions in the air will become carbonate ions. The container containing the tested solution must be clean and free from ion contamination. Before use, the electrode should be rinsed twice with deionized water (or distilled water) of less than 0.5 μ S/cm, and then rinsed with the test sample before measurement to ensure measurement accuracy.