How to Calibrate a TDS Meter

Tracy Morris

TDS stands for total dissolved solids. A TDS meter is a probe that consists of two metal probes that are inserted into water or hydroponic solutions to measure the amount of salt and minerals that are in the liquid. A TDS meter must be calibrated regularly to continue giving an accurate reading. If the meter is used every day, it should be calibrated once a week. If it is used less often, it should be calibrated once every two to three weeks. As battery life decreases, the meter loses calibration.

A TDS meter reads the ammount of minerals or salts dissolved in a liquid such as water.
  1. Rinse the probes of a TDS meter in clean water. Shake the water off of the meter and turn it on.

  2. Place the probes of the TDS meter into the liquid calibration solution up to a point between the "min" and "max" lines.

  3. Compare the reading of the meter with the reading on the bottle. If the two readings are not the same, insert a mini screwdriver into the back of the meter. The hole that you stick the screwdriver into is known as a trimmer pot.

  4. Turn the screwdriver clockwise to increase the reading of the TDS meter, or counterclockwise to decrease the reading. Adjust the meter until it matches the specifications of the calibration liquid.