37
087-0020 REV
E
has to do with some internal makeup of the sensor, which can deteriorate over time.
Although not normally expected, it is possible.
It is mandatory that any HF or Rock Solid Acid Gas sensor calibrated with chlorine also
be bumped tested with a acid gas. An easy source of this would be vinegar (acetic
acid). The use of HCI will eliminate the possibility of an unsafe calibration. Even if the
sensor were to suffer from this deterioration, it would show during calibration with HCI.
Special Span Calibration Requirements
Hydrides Calibration:
Hydride sensors
(AsH
3
/Arsine, PH
3
/Phosphine,
B
2
H
6
/Diborane, SiH
4
/Silane, GeH
4
/Germane)
exhibit a significant transient response to
changes of oxygen concentration. This response will not affect the sensor’s usefulness
when operating in normal atmospheric breathing air. However, when calibrating a
hydride sensor, hydride gases bottled in backgrounds other than 20.9% oxygen
should
not be used,
as the sensor
will see a change in oxygen background. For this reason,
permeation tube devices are recommended with normal air as a diluent.
Ammonia (NH
3
)Note:
It is acceptable to use ammonia sensors in reduced
oxygen environments (down to 2%) providing that the sensor is stored within the
environment for 24 hours prior to calibration in the same environment.
Weekly Operational Response Checks
These transmitters are designed to operate in many different environments. In some
extreme conditions, the sensor may become unresponsive to the target gas due to
continuous or excessive exposure to dust or dirt on the membrane, or very high/low
humidity conditions.
It is suggested that a sensor response test should be performed weekly to ensure
the transmitter continues to respond to the target gas.
It is recommended to briefly
expose the transmitter to a dose of the calibration gas used to span the instrument. A 5
to 10 second gas stream directed at the base of the sensor should suffice in producing a
response from the transmitter.
If response is slow (typical response time will be within 5 seconds), check the tip of the
sensor for either dirt buildup or condensation on the membrane. Both can cause slower
than normal operation. If an excessive dirt buildup is present, the sensor is generally not
repairable. If there is excessive moisture present, the sensor may be removed to a dry
area and permitted to dry. Under such conditions, the cause of the excessive moisture
should be determined and prevented (condensing humidity, wash-downs, etc.).
Refer to the appendix for alternative methods of generating operational check gases.
Failure Indications
Fault activation is indicated by flags on the Series 5000 Transmitter LCD. The following
are conditions upon which alarm flags will be activated:
Over Range Indication – “OR”
This flag will appear above the “OR” if the output goes above 110% of full scale.
Freedom 5000 Universal Analog Toxic Gas Detector
Instruction Manual