The working principle and precautions of the latest version of the conductivity meter

Introduction

The Conductivity Meter is a multi-range instrument that meets the requirements for a wide range of applications, from deionized water to seawater. This instrument provides automatic temperature compensation and a temperature coefficient, so it can be used to measure liquid samples with different temperature coefficients than water. It is capable of three ranges and has an automatic range selection function that automatically selects the most appropriate range for inspection.

A double-plug stainless steel conductivity electrode with built-in temperature sensor (for automatic temperature compensation), a rubber anti-slip sleeve, 4 alkaline AAA batteries, instrument operating manual and a portable soft case.

working principle

Conductivity is a digital representation of the ability of a solution to conduct current. The conductivity of water has a certain relationship with the amount of inorganic acids, bases and salts contained in it. When their concentration is low, the conductivity increases with the increase of concentration. Therefore, this index is often used to estimate the total amount of ions in water. Concentration or salt content.

Conductivity and water hardness

The conductivity of the aqueous solution is directly proportional to the concentration of dissolved solids, and the higher the concentration of solids, the greater the conductivity. The relationship between the conductivity and the dissolved solids concentration is approximately expressed as: 1.4 μS/cm = 1 ppm or 2 μS/cm = 1 ppm (per million units of CaCO3). The total hardness value of water can be obtained indirectly by using a conductivity meter or a total solids dissolution meter. As described above, for the convenience of approximate conversion, 1 μs/cm conductivity = 0.5 ppm hardness.

But need to pay attention:

(1) Indirectly measure the hardness of water by conductivity, the theoretical error is about 20-30ppm

(2) The conductivity of the solution determines the movement of the molecule, and the temperature affects the movement of the molecule. In order to compare the measurement results, the test temperature is generally set at 20 ° C or 25 ° C.

(3) The reagent hardness test can obtain the accurate water hardness value.

Soft and hard water

Water is divided into soft water and hard water. Any water that does not contain or contain a small amount of calcium and magnesium ions is called soft water, and vice versa. The hardness component of water, if it is caused by sodium bicarbonate or magnesium bicarbonate, is temporary hard water (boiled temporary hard water, decomposed sodium bicarbonate, precipitated insoluble carbonate, and water changes from hard water to soft water) If it is caused by calcium or magnesium containing sulfate or chloride, it is permanent hard water. According to the total hardness value of water, the total hardness is 0-30ppm, which is called soft water. The total hardness is more than 60ppm, which is called hard water. The high-quality drinking water does not exceed 25ppm, and the high-quality soft water has a total hardness of 10ppm or less. In natural water, away from the city, unpolluted rainwater and snowwater are soft water; spring water, stream water, river water, and reservoir water are mostly temporary hard water, and some groundwater is high hardness water.

Performance characteristics

● All Chinese display, friendly interface: All data, status and operation prompts are displayed in Chinese, and there is no symbol or code defined by the manufacturer.

●Simple menu structure, text-based human-table dialogue: It is clearer and more convenient to use, and can be operated according to the prompts on the screen.

● Multi-parameter simultaneous display: Simultaneous display of conductivity, output current, temperature, time and status.

●Automatic compensation of (super) pure water: For ultrapure water, the automatic temperature compensation of conductivity at 25 °C is realized.

● Notepad function: faithfully record the operation of the instrument and the occurrence time of the alarm, which is easy to manage.

● History curve and digital recorder function: The secondary meter automatically stores the measurement data every 5 minutes, and can continuously store the conductivity for one month.

● Digital clock function: displays the current time and provides a time reference for the digital recorder function.

●Backlight function: It can be used in an environment with dim light or no light. It automatically adjusts the contrast to the clearest according to temperature changes.

● Anti-program flight: The watchdog program ensures that the meter will not crash, which is the basic requirement of online instruments.

● Output current setting and checking function: Manual current source function, can check and arbitrarily set the output current value, which is convenient for detecting the recorder and the lower computer.

● Software setting current output mode: software selection is 0~10mA or 4~20mA output.

Advantages and disadvantages

The pen-shaped conductivity meter is generally made into a single range with a narrow measuring range and is a special and convenient instrument. The pen shape is also made into a TDS meter for measuring the quality of drinking water, and a salinity meter for measuring the salinity of the soup (solution).

Portable and laboratory conductivity meters have a wide measurement range and are commonly used instruments. The difference is that the portable DC power supply can be carried to the site. The laboratory conductivity meter has a wide measuring range, many functions and high measurement accuracy.

The industrial conductivity meter is characterized by good stability, reliable operation, certain measurement accuracy, strong environmental adaptability, strong anti-interference ability, analog output, digital communication, upper and lower limit alarm and control functions.

Precautions

Conductivity meter usage

Conductivity meter is an instrument for precise measurement of various liquid media. Conductivity meter is mainly used to accurately measure the conductivity value of liquid medium. When equipped with the corresponding constant electrode, the conductivity of high purity water can be accurately measured. Can be widely used in drinking water and sewage, chemical, petrochemical, pulp and paper, food and beverage, sugar, steel, surface treatment, steam power and electronics, semiconductor, pharmaceutical industry.

1. Check if the pointer refers to zero. If you do not refer to the zero adjustment knob on the conductivity meter,

2. Adjust the conductivity meter to the calibration file and point the pointer to the maximum scale.

3. Adjust the knob according to the electrode constant and adjust to the measurement file during measurement.

Precautions for use

1. The lead of the electrode should not be wet, otherwise it will not be measured.

2. High-purity water should be measured quickly after it is contained in the container, otherwise the conductivity will rise quickly because the CO2 in the air dissolves into the water and becomes carbonate ions.

3. The container containing the solution to be tested must be clean and free from ionic contamination.

Application field

●Power plant - water treatment;

● Water plant and sewage plant - wastewater treatment;

● Papermaking - production process / wastewater treatment;

●Chemical refining - production process / wastewater treatment;

● metallurgy and mining - production process / wastewater treatment;

● food and beverage - production process / wastewater treatment;

● Pharmaceutical industry - biological reaction and fermentation / wastewater treatment;

● Semiconductor - production process / wastewater treatment / high purity water production.

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