Normal Operation
A Polytron Pulsar 2 Open Path Gas Detector should always be re-zeroed
whenever it is re-sited, cleaned or re-aligned.
Normal Operation
The Dräger Polytron Pulsar 2 Open Path Gas Detector generates a 4-20mA signal,
proportional to the measured gas concentration, when the device configured for
analogue signal transmission. It can also be configured for digital transmission
through the use of HART.
Current
Meaning
20.5 mA
Over-range
4-20 mA
Measuring
3.5 mA
Pre-warning (dirty optics or mis-alignment)
2 mA
Beam Block
<1 mA
Fault
NOTE:
A sudden release of a large amount of pressurised and/or refrigerated gas
can result in a loss of visibility caused by condensation of atmospheric water
or the released gas itself. As true for all optical open path systems, this may
induce a beam block on the Dräger Polytron Pulsar Open Path Gas Detector
which will impair detector’s ability to detect the gas. The beam block warning
would be activated and reported to the user. Although the scenario is rather
unlikely, choosing shorter rather than longer path lengths when installing
Pulsars in this application can further reduce occurrence. In environments
where fog generated by gas leaks is a frequent problem, beam blocks should
be taken as indication for potential hazards and the use of additional point
detectors should be considered.
Other configurable settings in the Receiver, (such as the quantity of gas for full-
scale in the 4-20mA current loop, baseline deadband or auto zero tracking - AZT),
are less frequently changed and are often the same for all Dräger Polytron Pulsars
at the same site. The current values active in the Receiver can be read by selecting
SETS
in ‘Rx Main Menu’. A new configuration file can be written from the Hand
Held Terminal with
USER
in ‘Rx Memory Menu’. To see the settings that are available
to be sent, choose
SETS
in the ‘Not Connected’ menu. To change them, connect
the Dräger Hand Held Terminal to a computer in the non-hazardous area, go to
PC
in the ‘Not Connected’ menu, and run the Dräger software supplied.
AZT automatically cancels small deviations of gas reading that persist for a long
time. The rate is set in units of LEL.m/h. Baseline Dead-Band is the threshold
of gas readings that cause the analogue output to rise above either 4mA or the
Warning Current. AZT and baseline deadband settings should be chosen while
considering the ambient condition at the point of installation. In particular in harsh
outdoor environments where a slow increase of gas is not possible, higher AZT and
baseline deadband settings can be chosen. In indoor applications where small leaks
could lead to a slow increase of gas concentrations, AZT and baseline deadband
values must be kept at a low level.
NOTE:
The Dräger Polytron Pulsar is supplied with default configurations as listed
in the Specifications section of the Technical Manual. Any changes to these
default settings are carried out as part of the commissioning process.
Receiver AZT and Dead-Band default settings:
Auto Zero Tracking rate
range: 0 - 12 LFLm per hour
default: 0.05* LFLm per hour
Dead-Band
range: 0 - 0.5
default: LFLm 0.3** LFLm
*AZT default values or lower comply with EN 60079-29-4:2009 and the requirements of the DNV marine
approval (DNV except duct mount IFU).
Note: Default AZT settings on older Pulsars. This should be taken into account when replacing older units in
harsh environments.
** Default values or lower comply with EN 60079-29-4:2009 and the requirements of the DNV marine approval
(DNV except duct mount IFU).
Note: Default deadband settings on older Pulsars. This should be taken into account when replacing older
units in harsh environments.
