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6. OPERATION
6.1 Operation of the monitor
The S304 Emission Monitor measures the dust level in a gas stream by
monitoring electrostatic discharge when charged dust particles hit or pass by
the probe.
The signal generated by the electrostatic loaded particles is low-pass filtered
with a user selectable time constant to remove the effect of short variations,
and then converted into a current loop output signal. The user can trim the
output of the 4…20 mA signal can be calibrated.
The S304/S305 models include two independent alarm relays. The alarms are
arranged such that Alarm 1 is a low alarm, Alarm 2 is a high alarm. The alarms
can be delayed by means of a common time delay. The time is user selectable
in the range 0 to 180 seconds in 10 seconds increments.
The alarm threshold for each of the two alarms, are adjustable between 1 to
99% of the measuring range.
The relay output(s) change their state when the measured value for the dust
flow exceeds a user selected alarm trigger level. The relay output(s) are also
protected from the effect of short variations in the input signal with a user
selectable time constant common for both relays. Further the relays can also
be used to indicate internal errors during monitoring or to indicate when the
unit is in the service mode.
All the user selectable parameters are factory set to default values shown in
table 2. page 17.
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