Operation Manual HORIBA APDA-371
Particulate Monitor
Date:
April, 2010
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HORIBA Europe GmbH, Julius-Kronenberg-Str. 9, D-42799 Leichlingen,
: +49(0)2175-8978-0,
: +49(0)2175-8978-50
Page 36
cycle. This may not leave time for the membrane span check. Only one cycle per hour is allowed, regardless of
duration. Setting the value too long may cause the measurement to extend over into the next hour. Contact the Service
department before setting this to anything but the values shown in the table.
STATION #:
This is a station identification number. This number has a range of 00-99, and will be included
in the data reports. When used in a network, every APDA-371 should be given a different station number. Default value
is 01.
MET SAMPLE: This value is the averaging period for the data logger. It sets how often data is written to memory, and
can be set to 1,5,15, or 60 minutes. For example, if an external wind speed sensor is attached to the APDA, the MET
SAMPLE period could be set to 1 minute. This would cause the APDA to store an average of the WS reading every
minute. This value applies to all sensors attached to the unit. Warning: This setting will affect how long the memory
will last before getting full.
There are 4369 records available in the APDA memory. A MET SAMPLE period of 60 minutes (1 record per hour) will
result in over 182 days worth of memory capacity, but a 1 minute average period will fill up these memory records in
only 3 days. When the memory gets full the unit over-writes the oldest data. HORIBA recommends leaving the MET
SAMPLE period set at the default value of 60 minutes unless otherwise required for a particular application. The dust
concentration value will always be an hourly average regardless of this setting.
RANGE:
The RANGE setting sets the full-scale range of the concentration measurement system, including the
digital system and the analog voltage output. The RANGE value is almost never changed from the default setting of
1.000 mg. This means that the APDA measures a maximum full-scale range of 1000 micrograms above whatever the
OFFSET value is set to. The table below shows some examples of the RANGE setting interacting with the OFFSET
setting to produce the concentration data outputs of the APDA.
OFFSET
Setting
RANGE
Setting
Resulting Digital Data
Range
Resulting Analog
Output Range
-0.015 mg
1.000 mg
-0.015 to 0.985 mg
0-1V = -0.015 to 0.985 mg
-0.005 mg
1.000 mg
-0.005 to 0.995 mg
0-1V = -0.005 to 0.995 mg
0.000 mg
1.000 mg
0.000 to 1.000 mg
0-1V = 0.000 to 1.000 mg
0.000 mg
2.000 mg
0.000 to 2.000 mg
0-1V = 0.000 to 2.000 mg
In special cases, the RANGE value may be set to 0.100, 0.200, 0.250, 0.500, 2.000, 5.000, or 10.000 mg. Be sure to
account for this value if using a separate data logger to record the APDA-371 analog output.
Note: Changing the range setting will affect past data already stored to memory. Always download any old data before
changing settings, then clear the memory. Firmware version 3.2.4 or later will prompt you to clear the memory before
letting you change this setting.
OFFSET:
The OFFSET value is used to set the lower end of the APDA-371 measurement range, and could more
accurately be called a “range offset”. The new factory default value for OFFSET is now -0.015 mg. This causes the
entire range of the APDA-371 to shift down slightly so that it can read from -0.015 to 0.985 mg, instead of measuring
from 0 to 1.000 mg (assuming the RANGE is set to 1.000 mg). This simply allows the unit to measure slightly negative
concentration numbers near zero, which is helpful to differentiate between normal noise and a failure such as punctured
filter tape.
The previous default was -0.005 mg, and the value may still be set to -0.005 if needed to work with data logging
systems structured around the old setting. Some APDA users choose to set the OFFSET value to 0.000 to avoid
confusion, at the expense of not being able to see the true zero noise floor of the unit.
This value also affects the analog output, so that 0 to 1.000 volts equals -0.015 to 0.985 mg, instead of 0.000 to 1.000
mg. This is because the voltage output cannot go negative. You must take this scaling into account if an external data
logger is recording the APDA-371 analog output voltage. Contact the Service department if you plan to set the OFFSET
to any value other than -0.000, -0.005, or -0.015 mg.
Note: The OFFSET value is often misunderstood, and should not be confused with the BKGD (zero correction factor) or
the “e1” (lower concentration limit clamp) values. Be sure you understand all three of these settings!
