TAC-H
2
S/H
2
O/O
2
Pg. 6
TEXAS ANALYTICAL CONTROLS
4418 Bluebonnet Drive | Stafford, TX 77477 | (281) 240-4160 |
www.tac-controls.com
3 Start-up & Operation Overview
Standard In
Sample In
For H
2
S Measurement
• The microprocessor controls three electric solenoid valves— two sensor valves and
one stop valve.
• The microprocessor allows an inert (air) portion of the unit to purge a sample line to
the sensor; this normally takes about 75 seconds.
• Next, the microprocessor activates the electric solenoid valve, which passes the
process gas over the sensor for approximately 15 seconds.
• The microprocessor records the reaction rate of the sensor to the process gas,
comparing it to the established rate of the calibration gas.
• The microprocessor then switches to Sensor 2 and repeats the above steps, averaging
the two sensor readings and displaying the averaged reading. This completes the
measuring cycle.
• During calibration, turn the manual valve from the sample stream to the calibration
standard. Each sensor is calibrated twice.
For H
2
O Measurement
• The analyzer uses 1 H
2
O sensor to provide a continuous reading.
• The analyzer has a built in temperature controller to maintain an internal temperature between
95˚ and 100˚ degrees F. The display will show when the heater is on.
• The H
2
O readings may require approximately 24-48 hours to read, accurately.
• This time delay varies depending on the length of the sample line, how long it takes for the
temperature controller to reach 95˚ degrees, and how long it takes for the residual moisture in the
gas lines to clear.
For O
2
Measurement
• The O
2
readings are continuous.
• During calibration, turn the manual valve from the sample stream to the calibration standard.
Texas Analytical Controls is constantly striving to make improvements to the programs used in our
analyzers. Depending on when your analyzer was purchased some of the features illustrated in our
manuals may or may not be included. For an updated program call TAC at 281-240-4160.
The analyzer uses a 7-inch touchscreen programmable logic controller (PLC), with a removable microSD
card that data logs and stores the TAC program.
We describe below what happens inside the instrument at various stages of operation. Because the
sensors are proprietary devices, we don’t describe their operation, but we do describe how the sensors
measure the H
2
S, H
2
O, O
2
and CO
2
in a flowing gas stream.
The current delivered by the H
2
S sensor is fed to an analog device, which converts it to DC voltage. The
voltage is delivered to a microprocessor that measures the H
2
S in the flowing stream.
3.1 Function of the Microprocessor
