Hanna Instruments Dist 1 TDS pocket tester 

Model HI 98300: The DiST1 tester is a reliable, pocket-sized instruments that will give you quick and accurate readings of TDS. 

The casing of the popular DiST1 tester has been redesigned for increased strength, to better fit your hand and also offer a much larger LCD for easier viewing. The graphite sensors provide better repeatability since they do not oxidize.

The probe is user replaceable. In fact, the whole PCB module slides out and can be replaced. The casing has been shaped in such a way as to ease air bubbles out. The temperature sensor is exposed and provides faster response time.

Range: 0 to 1999 ppm with accuracy of ±2% F.S, using 1 point of calibration. The Hanna Instruments DiST1 model uses four 1.5V batteries (included) that provide approximately 150 hours of continuous use. Dimensions: 175 x 41 x 23 mm

Read Instruction Manual (PDF format - Lots of detail.)