General Description - ECD TC80 Instruction Manual

1.0 GENERAL DESCRIPTION

The TC80 is designed for use in drinking water, industrial cooling and
rinse water or other samples of fresh water that use chlorine in the
range of 0-20 ppm as a disinfectant. Chlorine is commonly added to
water as chlorine gas or sodium hypochlorite (bleach). Chlorine exists
in water as a pH dependent mixture of hypochlorous acid and
hypochlorite ion. The sum of these two components is referred to as
Free Chlorine. Organic compounds containing chlorine may be added
to the water or form in the water by reaction with the Free Chlorine.
Chlorine may also react with ammonia in the water to form
chloramines. Together these compounds are referred to as Bound or
Combined Chlorine.
Total Chlorine is the sum of the Bound Chlorine and Free Chlorine in the sample, the TC80 measures Total
Chlorine.
The TC80 is a complete system for measuring Total Chlorine. The panel mounted system includes a Constant
Head Flow Controller (CHFC), Total Chlorine sensor (TCS) and Flow Cell, pH sensor (S80pH) and Flow Cell and the
T80 Transmitter. Simply supply power to the T80 Transmitter and plumb the sample line in and the drain line
out and the TC80 is ready to use.
The CHFC maintains a constant sample flow to the pH and Chlorine flow cells. Pressure regulators and
rotameters are not needed to maintain a constant flow rate, the CHFC provides trouble free sample conditioning
between 10 and 80 gal/hr.
The Total Chlorine Sensor (TCS) is a three electrode amperometric sensor with a micro porous PTFE membrane,
a gold cathode, a silver/silver halide anode and a 304 SS counter electrode. The counter electrode design
provides a stable reference, virtually eliminating drift and the associated maintenance.
The T80 Transmitter applies a fixed voltage on the anode and cathode and measures the current flow.
Chlorine compounds diffuse through the PTFE membrane and react with a potassium iodide fill solution. The
iodide is oxidized to iodine by the various chlorine compounds. The iodine is then reduced (gains electrons) by
the gold cathode back to iodide ion. Silver on the anode is oxidized (donates electrons) to silver iodide
completing the current loop. With stable temperature, pH and sample flow, the current flow is proportional to
the total chlorine concentration.
Many competitive total chlorine analyzers require service on a monthly or bimonthly basis. The TCS is an
amperometric sensor that requires refilling every 3-6 months. The chloride concentration of the electrolyte
increases over time as the measured chlorine is reduced to chloride by the potassium iodide degrading the
electrolyte. The replaceable PTFE membrane is designed for long term stability and typically lasts over a year.
Replacing the PTFE membrane and recharging the electrolyte is easily accomplished without the use of tools.
The Model T80 transmitter can be 24 VDC powered or 100-240 VAC line powered. The standard configuration
has a 4-20 mA output and a RS485 serial communication port with MODBUS®RTU output. Alarm relays are
standard on either line powered transmitter.
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