Teledyne T101, Operation Manual, Page: 51 / 375

Teledyne ML – T101 Operation Manual Getting Started
47
The state of the zero/span valves can also be controlled:
•
Manually from the analyzer’s front panel by using the SIGNAL I/O
controls located under the DIAG Menu (Section 4.6.1),
• By activating the instrument’s AutoCal feature (Section 4.4.2),
• Remotely by using the external digital control inputs (Section 5.1.1.2 and
Section 6.7.1), or
• Remotely through the RS-232/485 serial I/O ports (see Appendix A for the
appropriate commands).
Sources of zero and span gas flow must be capable of supplying at least 600 cm
3
/min.
Both supply lines should be vented outside of the analyzer’s enclosure. In order to prevent
back-diffusion and pressure effects, these vent lines should be between 2 and 10 meters in
length.
INTERNAL ZERO/SPAN (IZS) VALVE GAS FLOW
The T101 can be equipped with an internal zero air and span gas generator (IZS). This
option includes a heated enclosure for a permeation tube for containing the calibration gas
under high pressure (not included; H
2
S perm tubes can be ordered from Teledyne ML;
SO
2
perm tubes must be ordered from a manufacturer), an external scrubber for
producing zero air and a set of valves for switching between the sample gas inlet and the
output of the zero/span subsystem, functionally very similar to the valves included in the
zero/span valve option.
Sources of zero and span gas flow must be capable of supplying at least 600 cm
3
/min.
Both supply lines should be vented outside of the analyzer’s enclosure. In order to prevent
back-diffusion and pressure effects, these vent lines should be between 2 and 10 meters in
length.
NOTE
The instrument can only be fitted with one type of permeation tube at a time. Therefore the IZS option can
only be used to calibrate or check the instrument for one gas, H
2
S or SO
2
, but not both.
External Zero Air Scrubber
The IZS option includes an external zero air scrubber assembly that removes all H
2
S the
zero air source. The scrubber is filled with activated charcoal.
The Permeation Source
Span gas is created when zero air passes over a permeation tube containing liquid H
2
S
under high pressure, which slowly permeates through a PTFE membrane into the
surrounding air. The speed at which the H
2
S permeates the membrane is called the
effusion rate. The concentration of the span gas is determined by three factors: membrane
size, sample gas temperature, and zero air flow rate
Size of the membrane : The larger the area of the membrane, the more permeation
occurs.