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BAM 1020-9800 Manual Rev W.docx
Page 49
6.9
HEATER Setup Screen
– RH Control Settings
The SETUP > HEATER screen is only visible if the HEATER CONTROL mode in the SETUP
> CALIBRATE menu is set to AUTO. This menu is used to configure the settings used by the
BAM 1020 to control the Smart Inlet Heater. The BAM 1020 uses an RH and temperature
sensor located below the filter tape in the sample air stream to monitor the conditions of the
air as it is being sampled. If the measured relative humidity of the sampled air stream is
higher than about 50% then PM measurements might be skewed higher those produced from
a collocated reference sampler. The Smart Heater can reduce this effect by actively heating
the inlet tube by warming the sampled air stream whenever the RH value measured
downstream of the filter tape exceeds a user selectable value.
It should be noted that the relative humidity downstream of the filter tape is not necessarily
the same as the ambient relative humidity. Relative humidity is a measure of how much
moisture the air is holding compared to how much moisture the air can hold (dew point) and
is strongly temperature dependent. For example, if the ambient relative humidity is 50% and
the ambient temperature is 3°C, the relative humidity downstream of the filter tape would be
about 22 % were the filter temperature 15°C, which means that the Smart Heater would not
have to apply additional heat were the BAM 1020 to be operated inside of a temperature-
controlled enclosure set maintain an instrument temperature of about 20 °C in order to
maintain the filter temperature RH value of 35%.
The SETUP > HEATER Screen
RH Control:
If YES is selected, the Smart Heater will be automatically turned on full power
whenever the humidity of the sample stream exceeds the RH Set point. When the RH falls
back below the set point, the heater turns down to a low power heat mode which applies only
slight heating. If this is set to NO, The Smart Heater will stay in low power mode and no
additional RH control will be performed.
RH Set point:
This is the relative humidity level that the filter will be regulated at or
below by the inlet heater. This value must be set to 35% for the version of the BAM 1020
employing the smart heater when operated as a PM2.5 US-EPA designated federal
equivalent method. The RH set point is set to 45% for European (EU) PM
2.5
units, and may
be either 35% or 45% for PM
10
units. The RH set point is otherwise adjustable from 10% to
99%.
Heater Setup
RH Control: YES
RH Setpoint: 35%
Datalog RH: YES (Chan 4)
Delta-T Control: NO
Delta-T Setpoint: 99 C
Datalog Delta-T: NO (Chan 5)
SAVE
EXIT