1. First understand what a conductivity meter is:
Electrical conductivity: The electrical conductivity of water is the reciprocal of the electrical resistance of water. It is usually used to express the purity of water. Electrical conductivity is the ability of an object to conduct electrical current. The measurement principle of the conductivity meter is to put two parallel plates in the solution to be measured, add a certain potential (usually a sine wave voltage) to both ends of the plate, and then measure the flow between the plates Current. According to Ohm's law, the reciprocal of conductivity (G)-resistance (R) is determined by voltage and current.
2. Next is the working unit of the conductivity meter:
The basic unit of conductance is Siemens (S), originally called Mho, which means the reciprocal of the resistance unit ohm. Because the geometry of the conductivity cell affects the conductivity value, the standard measurement uses the unit S / cm to represent the conductivity to compensate for the differences caused by the various electrode sizes. The unit conductivity (C) is simply the product of the measured conductivity (G) and the 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. = Ïl = l / σ
(1) Define or explain the reciprocal of resistivity as conductivity. σ = 1 / Ï;
(2) Unit: In the International System of Units, the unit of conductivity is Siemens / meter, and other units are: s / cm, us / cm. 1S / m = 0.01s / cm = 10000us / cm;
(3) Explain that the physical meaning of electrical conductivity is the performance of conducting electricity. The greater the electrical conductivity, the stronger the conductivity, and vice versa.
3. How to use the conductivity meter
Although each instrument has instructions, many friends will still encounter such troubles when using it. Let's share how to use it:
1. Before turning on the power switch, observe whether the hands are pointing at zero. Adjust the screws on the head to make the hands zero.
2. Move the calibration measurement switch to the "calibration" position.
3. Plug in the power cord, turn on the power switch, and warm up for a few minutes (until the pointer is completely stabilized) to adjust the "correction" regulator to make the meter indicate fullness.
4. When using the (1)-(8) range to measure the liquid with conductivity lower than 300μS.cm-1, select "low cycle", then move the high / low cycle switch to the low cycle. When using the (9)-(10) range to measure a liquid with a conductivity in the range of 300μS.cm-1 to 105μS.cm-1, it will be pulled to the “high cycleâ€.
5. Move the range selection switch to the required measurement range. If you don't know the conductivity of the solution to be measured in advance, you should first move it to the maximum conductivity measurement file, and then gradually lower it to prevent the hands from bending.
6. Use of electrode: Use the electrode clip to clamp the bakelite cap of the electrode, and fix the electrode clip on the electrode rod.
(1) When the conductivity of the tested solution is lower than 0.3μS.cm-1, use the DJS-0.1 type electrode, at this time, the "electrode constant compensation regulator" should be adjusted at the position of 10 times the matching electrode constant: for example If the matching cell constant is 0.090, it should be adjusted to the 0.90 position.
(2) When the conductivity of the tested solution is lower than 10μS.cm-1, use the DJS-0.1 type electrode, then the "electrode constant compensation regulator" should be adjusted to the corresponding position of the matching electrode constant: for example, matching If the cell constant is 0.95, it should be adjusted to the 0.95 position, and if the matching cell constant is 1.1, it should be adjusted to the 1.1 position.
7. Insert the electrode plug into the electrode socket, tighten the fastening screw on the socket, and then put the electrode into the solution to be tested.
8. Then calibrate [when measuring with (1)-(8) range, pull to low cycle when calibrating, when measuring with (9)-(12) range, then pull to high cycle], turn to "calibration ", Adjust the correction regulator so that the indication is at full scale.
9. When measuring high-purity water with (0-0.1) or (0-0.3) μS.cm-1, first insert the electrode lead into the electrode jack, and adjust the capacitance compensation regulator before the electrode enters the solution. The meter is indicated as the minimum value (this minimum value is the leakage resistance between the platinum plates of the electrodes. Due to the existence of this leakage resistance, the pointer of the meter cannot reach zero when adjusting the capacitance compensation regulator).
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