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TDS is an acronym that in English means total dissolved solids. A TDS meter is a meter that consists of two metal test tips that are inserted into water or hydroponic solutions to measure the amount of salt and minerals that are in the liquid. A TDS meter should be calibrated periodically to continue to produce an accurate reading. If the meter is used every day, it should be calibrated once a week. If used less frequently, it should be calibrated once every two to three weeks. As the battery decreases, the meter loses calibration. The total Dissolved Solids( TDS ) is the amount of the content of all inorganic and organic substances contained in a liquid.
Currently, it has become trendy in the world of aquariums to improve the water quality of the most delicate beings or with higher demands. Its use has become almost essential in marine aquariums, maintenance of discus fish or prawns, as well as in facilities where osmosis water is used.
More and more we find a meter for TDS in our hands and we realize the little or no information available for its calibration reliably, being forced to resort to the products available in the market. Those who have tried it know what I mean. These need to be calibrated every so often because their electrodes suffer variations. It is also advisable to perform a calibration to check its reliability before the first use since it could have left the factory with a deviation or suffer it in transport.
For the calibration of TDS equipment, a contrast liquid is used, of which the exact amount of dissolved solids is known, but we are not always in a position to find it in the market or to replace it when it is needed. Those of us who do not have the calibrated liquid at the end we are sticking blindly despite having a precision instrument.
To solve this problem, I have investigated the subject with the intention of finding contrast formulas or materials for walking around the house whose TDS level is known reliably. Although the task was not too simple, submerging in the world of chemistry has never been, I have achieved more than satisfactory results that I want to share, in addition to certain aspects to take into account for their care.
– OXYGENATED WATER 10 VOLUMES = 155 ppm.
– ETHYL ALCOHOL 96º = 35 ppm.
With these two solutions, we will have our TDS calibrated well. The oxygenated water will allow us to take a calibration reference that we can contrast with alcohol.
The alcohol only does not serve for the calibration because the meters do not have a negative scale (they do not mark less than zero). If we tried to perform a calibration using alcohol exclusively, we could be adjusting the device below zero and its screen would always mark zero.
OTHER NORMALIZED CONTRAST SOLUTIONS
Potassium chloride (KCl) solution in alcohol:
74.5 mg / l. of KCl = 73.5 ppm.
372.7 mg / l. of KCl = 358.9 ppm.
745.5 mg / l of KCl = 706.5 ppm.
Standardized water values
- Pure water 50 ppm.
- Mineral water between 100-200 ppm.
Tap water between 50 and 300 ppm.
NOTE: Concepts to be taken into account for the measurements
The conductivity varies according to the temperature of the liquid, so the contrast will always be made at the same temperature to avoid errors.
Adding fertilizers considerably increases the TDS, and so must be taken into account. When making subscribers, it is recommended to review the parameters again.
Basic care of the TDS meter
-For correct conservation and operation, it is necessary to avoid the oxidation of the electrode.
-When performing a measurement, the electrode is excited with the current. Being immersed in a liquid produces electrolysis that oxidizes and adheres to the salts contained in it, causing subsequent measurement errors.
-Drying the electrodes by blowing also causes oxidation, the saliva contains acids and salts that oxidize the metals.
-To carry out a proper cleaning, the use of alcohol is recommended, since it does not contain salts of any kind.
PD: That I have not found other calibration solutions does not mean they do not exist or know each other if someone knows any other and is willing to share it, I will gladly add it to the pots.