This is a Waltron/ABB μAI model 8231 fluoride monitor. The monitor uses a fluoride ion-selective and reference electrode pair mounted in a temperature controlled flowcell. Pre-treatment of the sample with a reagent solution is carried out to adjust the pH, decomplex the fluoride ions in solution and remove the effects of changes in ionic strength in the sample. Range of measurement can be set to any two consecutive decades of concentration between 0.1 and 1000mgl . The current outputs can be used to view any window within the range to which the instrument is set, e.g. in control of fluoridation where a window of 0.1 to 1.5mgl provides optimum discrimination at the control point, i.e. 1mgl , along with maximum visibility of alarm conditions. Alarm contacts are provided which can be set to suitable values, e.g. 1.2mgl to initiate a shutdown of the dosing system if this value is exceeded. Programmable delay and hysteresis functions avoid spurious alarms which can cause problems with the control plant. Under such typical circumstances, with appropriate standard solutions and calibration frequencies, accuracies better than ±5% of reading or ±0.1mgl , whichever is the greater, can be achieved.