Digital TDS Meter & Thermometer Water Quality Tester Best For: Hydroponics - Water Filters - Aquarium - Reverse Osmosis - Coffee Smallest & Lightest Meter Sold Auto Temperature Control EZ Stop wasting money on unnecessary water filter purchases with Tip Top Measure's TTM-A1A meter. Has HOLD for convenient reading & AUTO OFF to save battery. PreCalibrated at 342 ppm NaCl. Advanced microprocessor uses Automatic Temperature Control to ensure accuracy. Extended range of 0-9990 ppm, at a resolution of 1 ppm from 0-999 and 10 ppm from 1000-9990. We stand behind our high-quality products with a 5 year warranty.