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Handheld TDS Meter

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The TDS-3 Handheld TDS Meter from HM Digital is a useful tool to spot check the TDS of your home water supply or RO/DI unit output. This unit features a digital display, built in thermometer, and comes with a carrying case.   The TDS-3 comes factory calibrated.



TDS-3 is the most widely used handheld TDS meter in the world for hand held testing of TDS,  the contaminant removed by the Reverse Osmosis (RO)Membrane itself.  The TDS-3 Meter can be used to test membrane effectiveness, as well as DI Resin performance.  This meter can be used to measure the effectiveness of the membrane.  To perform a test on a membrane (2) samples must be drawn. The first is untreated water and the other is RO treated water. Use the TDS reading to calculate a removal ratio. MERO Thin Film Composite (TFC) Membranes are effective for 95-98% removal of TDS when new.  Replace at 85% removal.  This meter can also be used to test the DI Resin performance.  Water exiting the DI Resin should have zero TDS.  Replace DI as this number rises.


  • Ideal for commercial use. Includes a carrying case with belt clip.
  • Highly efficient and accurate due to its advanced microprocessor technology.
  • Hold Function: saves measurements for convenient reading and recording.
  • Auto-off function: the meter shuts off automatically after 10 minutes of non-use to conserve batteries.
  • Measurement Range: 0-9990 ppm. From 0-999 ppm, the resolution is in increments of 1ppm. From 1000 to 9990 ppm, the resolution is in increments of 10ppm, indicated by a blinking ‘x10’ image.
  • Built-in digital thermometer
  • Display: large and easy-to-read LCD screen.
  • Factory Calibrated: our meters are calibrated with a 342 ppm NaCl solution. Meters can be recalibrated with a mini-screwdriver.


  • Resolution: 1 ppm, 1 degree Celsius (also available in 10 ppm)
  • Accuracy: ±2%
  • Power source: 2 x 1.5V button cell batteries (included)
  • Battery life: 1000 hours of usage


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