Handheld Meters

What is TDS?

Total Dissolved Solids (TDS) are the total amount of mobile charged ions, including minerals, salts or metals, dissolved in a given volume of water, and expressed in units of mg per unit volume of water (mg/L), also referred to as parts per million (ppm).

How Does a TDS Meter Work

TDS meters are really conductivity meters. The way a TDS meter works is by applying a voltage between two or more electrodes. By applying this voltage, the negatively charged ions will move towards the positive charged electrode, and positive charged ions towards the negative electrode. The TDS tester monitors the amount of current passing between the two electrodes as a gauge of how many ions are in solution, and allows you to calculate the TDS reading.

Tips for Using a TDS Meter

1. Rinse the end of the TDS meter that is being submerged in water with the freshest water that is available. Buildup of salts on the meter will interfere with proper operation, and can skew the readings.
2. Do not touch the TDS electrode surfaces with hands or abrasive cloth.
3. To Clean the TDS electrodes, you can soak the tips in vinegar or diluted hydrochloric acid (muriatic acid) and then rinsing well with water. Check your TDS meter handbook for individual cleaning methods.
4. If you are using a TDS meter to monitor the performance of an RO membrane, then the TDS measured value should decrease by at least a factor of 10 from the starting tap water. For example, if water out of your tap is 231 ppm, then the water from your RO system should be less than 23 ppm. In many instances, a drop of less than a factor of 10 indicates a problem with the RO membrane.
   

TDS Meter Comparison Charts

Model Name	Temp. Function	Water Resistant	Digital Display	Range ppm(mg/L)
TDS-ZT2				0 - 999
TDS-EZ				0 - 999
TDS-3				0 - 999
TDS-4				0 - 999
TDS-4TM				0 - 999
HMAP-1				0 - 5000
HMEC-3				0 - 999
HMAP-2				0 - 999
COM-100				0 - 999
PH-200				0 - 999
HI98121				0 - 999
ORP-200				0 - 999
HI98129				0 - 999