HM Digital TDS-3 Handheld TDS Meter | 0-9990 ppm, Thermometer, Case

HM Digital TDS-3 Pocket Meter for Water and Nutrients

This is a pocket-size meter that reads total dissolved solids from 0 to 9990 ppm. It resolves to 1 ppm up to 999 ppm, then switches to 10 ppm steps above 1,000, shown by an x10 icon. The meter is rated at ±2% accuracy across its range. A built-in thermometer reads water temperature from 0 to 80°C in 0.1° steps. Automatic temperature compensation covers 1 to 50°C, so readings stay consistent as solution temperature shifts. The meter uses the NaCl conversion factor, averaging 0.5, and comes factory calibrated at 342 ppm NaCl. If it drifts, it can be recalibrated with a small screwdriver against a matching NaCl solution. A hold button freezes the reading so you can lift the probe and record it. To save batteries, the meter shuts itself off after 10 minutes without use. Two LR44 button cells come installed and last around 1,000 hours. It measures 6.1 x 1.25 x 1 in and weighs about 2 oz, with a black vinyl belt-clip case included.

Getting Accurate Readings From a Handheld TDS Meter

A handheld TDS meter earns its place at three checkpoints: source water, the mixed reservoir and runoff. Read the source first, since tap water alone can carry a few hundred ppm before any nutrients go in. Mix the batch, stir well, then take the reading once the solution has settled. Dip the probe to the immersion line and swirl gently to clear bubbles off the electrodes. Wait for the display to stop moving, press hold, and lift the meter out to read it. Rinse the probe in clean water after every test so salts don't build up. Remember that the meter reads on a 0.5 scale. Feed charts written on a 0.7 scale will show higher numbers for the same solution, so convert before comparing. HM Digital suggests calibrating near the upper third of the range you test most. For a reservoir run around 800 to 1,200 ppm, a mid-range NaCl standard keeps readings honest. Recheck calibration every few months and whenever readings stop matching your feed chart. Store the meter in its case with the cap on.

Key Features

• 0-9990 ppm Range: Covers RO water, tap water and full-strength nutrient solution.
• ±2% Accuracy: With 1 ppm resolution up to 999 ppm and 10 ppm steps above.
• Built-In Thermometer: Reads 0 to 80°C, with automatic temperature compensation from 1 to 50°C.
• Hold Function: Freezes the reading so it can be recorded after the probe is lifted.
• Factory Calibrated: Set at 342 ppm NaCl and adjustable with a mini screwdriver.
• Auto-Off and Long Battery Life: Shuts off after 10 minutes idle; two LR44 cells last about 1,000 hours.

Technical Specifications