Easier to use and more accurate than chemical test kitsPhenanthroline method Accuracy ±0.04 ppm (mg/L) ±2% of reading 0.01 ppm (mg/L) resolution (250 points)Large, easy to read digits Auto shut-off.Dedicated to a single parameterDesigned to work with HANNA's powder reagents Uses 10 mL glass cuvettes.Small Size, Big ConvenienceWeighing a mere 65g (2.3 oz.), the Checker®HC easily fits into the palm of your hand or pocket.Use for quick and accurate on the spot analysis.Single button operation: Zero and Measure Operated by a single AAA battery.ACCURATE AND AFFORDABLE IRON MEASUREMENTThe HANNA HI 721 Checker®HC bridges the gap between simple chemical test kits and professional instrumentation. Chemical test kits are not very accurate and only give 5 to 10 points resolution while professional instrumentation can cost hundreds of dollars and can be time consuming to calibrate and maintain. The HANNA HI 721 Checker®HC is accurate and affordable with immediate results. The new HI 721 Checker®HC portable handheld colorimeter features a resolution of 0.01 ppm (250 points) and 2% ±0.04 ppm accuracy of reading. The HI 721 Checker®HC uses an adaptation of Standard Method 3500-Fe B. The contoured style of this Checker®HC fits in your palm and pocket perfectly and the large LCD is easy to read. The auto shut-off feature assures the battery life will not be drained if you forget to turn it off. The HI 721 Checker®HC is extremely simple to use. First, zero the instrument with your water sample. Next, add the reagent. Last, Place the vial into the HI 721 Checker®HC, press the button and read the results. It’s that easy.