You bought an EC meter.
While EC and TDS are often used synonymously, there are some important differences to note. EC, when applied to water, refers to the electrical charge of a given water sample. TDS refers to the total amount of substances in the water other than the pure H2O. The only true way of measuring TDS is to evaporate the water and weigh what’s left. Since this is near impossible to do for the average person, is it possible to estimate the TDS level by measuring the EC of the water. Every digital TDS meter in the world is actually an EC meter.
Don't know what the reading should be.
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