Instruction manual

MODEL XMT-A-FF/FI SECTION 7.0
PROGRAMMING THE TRANSMITTER
7.3 CHOOSING AND CONFIGURING THE ANALYTICAL MEASUREMENT
7.3.1 Purpose
This section describes how to do the following:
1. Configure the transmitter to measure oxygen, ozone, free chlorine, total chlorine, or monochloramine.
2. Choose the concentration units to be displayed
3. Set an input filter for the raw sensor current.
4. If oxygen was selected, there are additional selections to make.
a. identify the type of sensor being used
b. choose the units in which barometric pressure will be displayed
c. select a process pressure for calculating % saturation
d. enter the salinity of the process liquid
5. If free chlorine was selected, there are additional selections and settings to make.
a. choose automatic or manual pH correction
b. configure the pH sensor if automatic pH correction was selected
c. choose single or dual slope calibration
6. If total chlorine was selected, single or dual slope calibration must also be specified.
7.3.2 Definitions
1. MEASUREMENT. The transmitter can be configured to measure dissolve oxygen (ppm and ppb level), free chlorine,
total chlorine, monochloramine, and ozone.
2. FREE CHLORINE. Free chlorine is the product of adding sodium hypochlorite (bleach) or chlorine gas to fresh water.
Free chlorine is the sum of hypochlorous acid (HOCl) and hypochlorite ion (OCl
-
).
3. TOTAL CHLORINE. Total chlorine is the sum of free and combined chlorine. Combined chlorine generally refers to
chlorine oxidants in which chlorine is combined with ammonia or organic amines. The term total chlorine also refers to
other chlorine oxidants such as chlorine dioxide. To measure total chlorine, the sample must first be treated with acetic
acid and potassium iodide. Total chlorine reacts with iodide to produce an equivalent amount of iodine, which the sen-
sor measures.
4. MONOCHLORAMINE. Monochloramine (NH
2
Cl) is commonly used in the United States for disinfecting drinking water.
It is made by first treating the water with ammonia followed by just the exact amount of chlorine to completely react
with the ammonia. Monochloramine is a useful disinfectant in waters that have a tendency to produce trihalomethanes
(THMs) when treated free chlorine.
5. BAROMETRIC PRESSURE (DISSOLVED OXYGEN ONLY). Dissolved oxygen sensors are usually calibrated by
exposing them to air. The sensor current in air is exactly the same as the current when the sensor is in water saturat-
ed with air. The maximum solubility of atmospheric oxygen in water depends on temperature and barometric pressure.
A temperature device in the oxygen sensor measures temperature. The user must enter the barometric pressure.
6. PERCENT SATURATION (DISSOLVED OXYGEN ONLY). Percent saturation is the ratio of the concentration of dis-
solved oxygen in a sample to the maximum amount of oxygen the sample can hold at the same temperature. Pressure
also affects the percent saturation. Usually, percent saturation is calculated using the barometric pressure during cal-
ibration. If the user desires, percent saturation can also be calculated using the process pressure.
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