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HM Digital Handheld TDS Meter & Thermometer

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  •   Model # TDS-3
  •   UPC 712542177903
  •   Brand HM Digital

TDS-3 is the most widely used handheld TDS meter in the world according to HM Digital who holds the original patent for this meter. Beware of imitators, none offer the superior performance of the original TDS-3.

TDS-3 Meters measure the amount of Total Dissolved Solids (TDS) within a given sample of water. The measurement is shown in Parts Per Million (PPM).

TDS is the contaminant category removed by the Reverse Osmosis (RO)Membrane itself. The meter can be used to measure the effectiveness of the membrane only and not the filters used in conjunction with it.

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. Most Thin Film Composite (TFC) Membranes are effective for 95-98% removal of TDS.


  • 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.


  • TDS Range: 0 - 9990 ppm (mg/L)
  • Temp. Range: 0 - 80 degrees Celsius
  • Resolution: 1 ppm, 1 degree Celsius (also available in 10 ppm)
  • Accuracy: ±2%
  • ATC: Built-in sensor for Automatic Temperature Compensation of 1 to 50 degrees Celsius (33 to 122 degrees Fahrenheit)
  • Power source: 2 x 1.5V button cell batteries (included)
  • Battery life: 1000 hours of usage
  • Dimensions: 15.5 x 3.1 x 2.3cm (6.1 x 1.25 x 1 inches)
  • Weight with case: 76.5g (2.7 oz)
  • Weight without case: 56.7g (2 oz)