The Hanna Instruments HI 98129 is a multi-parameter tester that measures pH, electro-conductivity (EC), total dissolved solids (TDS), and temperature, and features automatic temperature compensation (ATC), an LCD screen, automatic shut-off, and a waterproof body that floats in water. The tester automatically compensates for the effects of temperature when taking pH and EC/TDS readings, so additional measurements and manual temperature entries are unnecessary. The HI 98129 meter has a replaceable pH electrode with an extendable cloth junction, and an EC/TDS graphite electrode that is resistant to salts and other corrosives. These features extend the life of the meter by allowing for replacement of the electrodes. Calibration is automatic at one or two points, with two sets of memorized buffer values (pH 4.01/7.01/10.01 or 4.01/6.86/9.18). The EC/TDS conversion factor and temperature compensation coefficient (&Beta) is user-selectable. The tester functions in temperatures of 0.0 to 60.0 degrees C/32.0 to 140.0 degrees F (+ or - 0.5 degrees C/1 degree F), and has a range of pH 0.0 to 14.0 (+ or - 0.05 pH). EC range is 0 to 3999 uS/cm, TDS range is 0 to 2000 ppm (+ or - 2% F.S), with respective resolutions 1 uS/cm and 1 ppm. At 3.5 ounces and 8.3 x 2.7 x 1.3 inches (H x W x D), the HI 98129 is sized for taking measurements in the field. (H is height, the vertical distance from lowest to highest point; W is width, the horizontal distance from left to right; D is depth, the horizontal distance from front to back.) pH testers measure the acidity or alkalinity of a substance and are commonly used by researchers, manufacturers, and hobbyists. Hanna Instruments manufactures analytical instrumentation and supplies, including pH meters, electrodes, chemical reagents, and buffer solutions. The company, founded in 1978 and headquartered in Woonsocket, RI, meets International Organization for Standardization (ISO) 9001 standards. What’s in the Box? HI 98129 meter Protective cap Electrode removal tool Four 1.5V batteries Instructions