Nitrate Low Range Checker HI764. The HI 764 is a portable meter for measuring nitrite in water samples. The meter has a range of 0 to 200 ppb + or - 4% of the reading (+ or - 10 ppb), with resolution 1 ppb. It operates in temperatures from 0 to 50 degrees C (32 to 122 degrees F)/RH max 95%. The device operates on one 1.5V AAA battery, with an auto-off function that shuts off the device after two minutes of non-use.Dimensions are 81.5 x 61 x 37.5 mm  (3.2 x 2.4 x 1.5”) and weighs 64 g (2.25 oz.).