ATI
Model A15/82 Fluoride Monitor with Auto-Calibration
5
O&M Manual
Rev-G (6/10)
INTRODUCTION
The Model A15/82 is an on-line monitoring system designed for the continuous measurement of the
fluoride ion (F
-
) in aqueous solutions. The monitoring system provides measurements between 0.1 and 1000
PPM. The unit is set up at the factory for a default range of 0-10 PPM, but can be changed to higher ranges of
0-100 or 0-1000 PPM by proper field calibration. The analog output signal may be spanned for smaller ranges
within the overall operating ranges if desired. A15/82 monitors are designed to operate on sample temperatures
from 0
°
to 50
°
C. Because water is flowing through the chemistry module at a low rate, this unit cannot be
exposed to temperatures below 0
°
C.
The basic sensing element used in the monitor is a fluoride ion selective electrode (ISE). This sensor
contains a lanthanum fluoride crystal that generates a voltage proportional to the activity of fluoride ion in
solution. A silver/silver chloride reference electrode contained in the same sensor body provides the second half
of the measurement cell. Because ISE electrodes respond to activity rather than concentration, a small amount
of buffer is metered into the sample to provide a constant background condition. With other parameters held
constant, fluoride activity and fluoride concentration are closely related. A temperature element in the
measuring chamber provides automatic temperature compensation for the system.
A15/82 monitors incorporate an automatic calibration feature that maintains high measurement accuracy
over long operating periods. The automatic calibration system feeds a known fluoride standard into the system
at an operator programmable frequency such as every 24 hours, every 3 days, or some other convenient
interval. Automatic calibration can be done at any interval between 1 and 999 hours. During calibration, analog
output and relays are held at the values measured just before initiation of the calibration sequence. An alarm
relay can be used to indicate a calibration failure.
Fluoride monitoring system includes 3 parts, an electronic display unit (panel or wall mount), a chemistry
module, and a sample inlet and drain chamber. A typical fluoride system installation is shown in Figure 1. A
stainless steel mounting panel is available (part number 00-1261) that simplifies installation and locates analyzer
components in their proper relative positions. In addition, the plate contains a convenient pan for locating the
reagent and calibration standard.
