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Reference Manual
00809-0200-3415
1
Description and specifications
1.1
Features
Rosemount TCL Sample Conditioning System
The sample conditioning system permits a single sensor to measure total chlorine in water.
The sample conditioning system continuously injects a solution of acetic acid (vinegar)
and potassium iodide into the sample. The acid lowers the pH to between 3.5 and 4.5
and allows total chlorine in the sample to quantitatively react with the potassium iodide
to produce iodine. The sensor measures the iodine concentration, and the transmitter
displays the total oxidant concentration in ppm as Cl
Rosemount 56 Transmitter
The is housed in a corrosion resistant NEMA 4X enclosure. It is suitable for panel, pipe, or
wall mounting. You can operate the transmitter with a membrane keypad.
and programming screens are simple and intuitive. Plain language prompts in languages
guide you.
Four fully programmable relays are available.
Rosemount 499ACL-02 Total Chlorine Sensor
The Rosemount 499ACL-02 Total Chlorine Sensor is used in the TCL Sample Conditioning
System. Although the sensor is called a chlorine sensor, it really measures iodine. The
iodine comes from the reaction between oxidants in the sample and the acetic acid/
potassium iodide reagent added by the sample conditioning system.
The sensor consists of a gold cathode and a silver anode in an electrolyte solution. A
silicone membrane, permeable to iodine, is stretched over the cathode. The transmitter
applies a voltage to the cathode sufficiently negative to reduce all the iodine reaching it.
Because the concentration of iodine in the sensor is always zero, a concentration gradient
continuously forces iodine from the sample through the membrane into the sensor.
The reduction of iodine in the sensor generates a current directly proportional to the
diffusion rate of iodine through the membrane, which is directly proportional to the
concentration of iodine in the sample. Because the iodine concentration depends on the
amount of total chlorine in the sample, the sensor current is ultimately proportional to the
total chlorine concentration.
The permeability of the membrane to iodine is a function of temperature. A Pt100 RTD
in the sensor measures the temperature, and the transmitter uses the temperature to
compensate the total chlorine reading for changes in membrane permeability.
Sensor maintenance is fast and easy. Replacing the membrane requires no special tools
or fixtures. Simply place the membrane assembly on the cathode and screw the retainer
in place. Installing a new membrane and replenishing the electrolyte takes only a few
minutes.
1.2
Specifications
Rosemount TCL 56
Description and specifications
.
2
January 2023
7
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Table of Contents
Troubleshooting
