Portable pH/ISE allow the flexibility to perform an ISE measurement with a portable. It is a laboratory measurement that requires the addition of the ISA to fix the ion activity in the sample and the use of a magnetic stirrer to keep the sample homogenous. The portable pH/ISE meter has the ion charge and formula weight pre-programmed for concentration measurements. Also availabe multi-parameter portable meters that measure pH, ORP, dissolved oxygen, conductivity, ammonium, chloride, and nitrate. The multi-parameter portables can be ordered with probes that can also measure turbidity and meters that have built-in GPS for data mapping.