Content1. What is salinity meter?
1.1 Working principle of salinity meter
1.2 Unit conversion in salinity meter
1.3 Difference between salinity meter and hydrometer2. Type of salinity meter
2.1 Salinity tester3. How to use a salinity meter for measurement?
3.1 Salino meter4. Use of salinity meter
4.1 Calibration of salinity meter
5. How to buy salinity meter?
What is salinity meter?
, also known as salinometer
, salinity tester
, and salino meter
, is an instrument used to quickly determine the concentration or refractive index of salt (sodium chloride
) solutions by weight percent ratio. It is widely used in salt, food, beverage, and other industrial sectors as well as in agricultural production and scientific research. It usually consists of a sensor, a measurement circuit, and a data processing device. There are two types of conductivity sensors: electrode type and induction type.
The salinity meter
is commonly used in desalination units on board ships as a continuous instrument for detecting the salinity of the freshwater produced and can give audible and visual alarms when the salinity exceeds the established standard while causing the out-of-specification fresh water to be automatically returned to the still or drained into the bilge.
The sensor of the salinity meter
consists of a pair of electrodes coated with a layer of physically and chemically stable platinum or rhodium (not easily corroded). To prevent the electrodes of the sensor from short-circuiting due to the adhesion of foreign substances, the sensor should be cleaned once every month or so. When cleaning, wipe with a soft cloth, and do not scrape with hard objects to not damage the platinum or rhodium coating.
The salt content meter
is easy to operate, and the user can quickly read the salt concentration or the specific gravity of seawater. It can be applied to the concentration management of seawater used in oceans, fisheries, farms, seawater used in aquariums or artificial seawater, brine used for storing fish, etc.
Working principle of salinity meter
The conductivity of aqueous solutions increases with the increase of salt content, that is, the greater the salt content, the smaller the resistance, and the better the conductivity. When light from one medium into another medium will produce a refraction phenomenon, and the ratio of the sine of the angle of incidence is constant, this ratio is called refractive index.
The refractive index
of a salt solution can be determined by using the property that the content of soluble substances in the salt solution is proportional to the refractive index under ordinary circumstances so that the concentration of salt can be calculated.
Unit conversion in salinity meter
According to the current market appeared many kinds of salinometers, according to their use of different environments, salinometers that take salinity units are not the same. Here is a summary of the common salinometer units on the market, and the conversion relationship between them.
% - This unit is the most common and easy to understand, for example, 2% salinity, meaning 100g of salt water, containing 2g of salt, the ratio is 2g/100g, about the unit g, it is equal to 2%.
ppm - ppm=part per million, meaning one part per million.
ppt - this salinity unit salinometer laboratory use more, ppt = part per thousand, meaning one thousandth.
Difference between salinity meter and hydrometer
The specific gravity meter is made according to Archimedes' law and the condition that the object floats in equilibrium on the liquid surface, and is an instrument for determining the density of liquids. It uses a closed glass tube, one end of uniform thickness, the inner wall is attached to the scale paper, the other end is slightly inflated in the shape of a bubble, the bubble is equipped with small lead particles or mercury, so that the glass tube can be tested in the liquid vertically immersed to a sufficient depth, and can float steadily in the liquid, that is, when it is subjected to any shaking, can automatically return to a vertical position of rest. When the hydrometer floats in the liquid, its gravity is equal to the gravity of the liquid it is discharged. So in different liquids immersed in different depths, the pressure is different, and the specific gravity meter is used for this relationship scale.
Type of salinity meter
Salinity meters can be divided into two types field salt content meters and laboratory salt content meters according to usage, and the measurement range is from 2 to 40.
A. On-site salinity meter
Salinity meter is an instrument that can measure and record the spatial and temporal changes in the on-site salinity of seawater with a measurement accuracy of about ±0.02.
There are two types of measurement circuits: one with automatic temperature and pressure compensation circuits; and one without compensation circuits, which instead input the measured values of temperature, depth, and conductivity into the computer and convert them into practical salinity.
B. Laboratory salinity meter
A high-precision salinity meter with a measurement accuracy of about ±0.005. It can measure water samples at constant temperature and is also available with a temperature compensation circuit.
Conductivity sensors are electrode type and induction type: the former is equipped with two or more electrodes on the conductivity cell, the most typical is equipped with a pair of current poles and a pair of potential poles of the four-pole sensor; the latter couples two coaxial toroidal transformers through the single-turn seawater circuit inside and outside the conductivity cell, using the principle that the degree of coupling is proportional to the conductivity of seawater for measurement.
How to use a salinity meter for measurement?
Salinity meter is a precision optical instrument used to measure the concentration of salt in liquids. It has the characteristics of simple operation, convenient, easy to use, less measuring liquid, accurate and rapid. Seawater measuring salinometers can be divided into three main categories: optical salinometer, glass float meter, digital salinity tester, etc. Here we will introduce the characteristics of each category and the influence of temperature on the salinometer in detail.
A. Optical salinity meter
The optical method uses the principle of refraction of light to determine salinity based on the principle that liquids of different concentrations have different refractive indices. This type of salinity meter is simple to operate, just covers the solution to be measured evenly on the prism, and ensures that the temperature of the solution is the same as the temperature of the prism, through photoelectric conversion or visual method, the user can quickly read the salt concentration.
Note: Wash and dry with pure water for storage after use, otherwise it will affect the service life. It should be calibrated before each use.
Here are the steps of optical salinometer calibration.
a. Wash the optical salinometer with pure water before use. (Try not to touch the prism directly with your hands, because there is also salinity on your hands)
b. If the scale is not in the position of 1.000 then left and right screw calibration to the scale.
B. Glass float meter
a. Before use, check whether the specific gravity meter and the glass casing are broken, whether the rubber is damaged, and whether the positioning hole is loose.
b. Put the specific gravity meter into the glass tube, and set a good pipette, with a scale end upward into it.
c. Squeeze the top rubber flat, then vertically put the tube in the measured liquid slowly relax the squeezed rubber hand, and the liquid is sucked into the glass tube.
d. When the liquid in the tube exceeds 1cm of the positioning hole of the specific gravity meter, stop absorbing liquid.
e. The scale of the current horizontal surface hydrometer is the specific gravity of the measured liquid.
f. If the specific gravity of the measured liquid is greater than or less than the specified value, we must re-ratio the specific gravity of the liquid, and then measure again, until it meets the specified value.
g. After the measurement, clean the hydrometer with alcohol and store it well for the next measurement.
C. Digital salinity tester
Digital salinity tester is the ideal instrument for measuring the salinity of aqueous solutions. The instrument automatically selects the appropriate range. The lowest range has a resolution of 0.001 ppt to 1 ppm. The cell constantly flashes on the digital display and can be adjusted from the front panel. Using known standard solutions, facilities are also available for the automatic measurement of cell constants.
Use of salinity meter
Salinity meter is designed according to the principle that liquids of different concentrations have different refractive indices, and it is an instrument that uses light to test liquids. The use of a salinity tester is as follows.
a. Wipe the mirror surface of the refractometer clean.
b. Use the dropper to suck a drop of seawater from the seawater tank about 2~3cc.
c. Open the spotting plate and attach a drop of seawater to the receiving mirror, then lightly cover the spotting plate.
d. Place the refractometer with the spotting plate facing the light source, and keep the eyepiece close to the eyes and parallel.
e. Observe the scale on the refractometer by the viewing window and record the calibration method of the seawater salinometer.
Calibration of salinity meter
a. When using the handheld salinometer, hold the rubber sleeve with the four fingers of the left hand, and adjust the eyepiece with the right hand to prevent the body temperature from entering the instrument and affecting the measurement accuracy.
b. Open the inlet plate and clean the refractive prism with soft flannel.
c. Several drops of distilled water, drops in the refractive prism, gently close the light into the plate, so that the solution is evenly distributed on the surface of the prism, and the instrument into the light plate aligned with the light source or bright, the eye through the eyepiece to observe the field of view, if the field of view is not clear, then rotate the eyepiece, so that the field of view is clear, and then rotate the zero correction screw, so that the light and dark dividing line placed at zero. Then wipe the distilled water, and replace the test solution, at this time, the field of view of the line of demarcation, the corresponding division of the scale value is the test solution concentration value and density value.
How to buy salinity meter?
ANTITECK provide lab equipment, lab consumable, manufacturing equipment in life sciences sector.
If you are interested in our salinity meter or have any questions, please write an e-mail to firstname.lastname@example.org, we will reply to you as soon as possible.