BAM 1020-9800 Manual Rev W.docx
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8.4 Interfacing a Digital Data logger with the BAM 1020
Many BAM 1020 users configure an external digital data logger to retrieve data from the BAM
1020. This typically requires some programming experience with the particular type of digital
logger to be used. Several environmental data logger manufacturers supply pre-made BAM
1020 drivers for basic data collection applications. All digital files from the BAM 1020 must be
obtained through the RS-232 port or the newer REPORT serial port, or in some cases from
the PRINTER port. The BAM 1020 digital files are described in Section 9.
The most common method is to program the digital logger to request the last hourly comma-
separated data record array from the BAM 1020, once per hour, using the RS-232 or
REPORT port. In this case, the logger must establish connection with the BAM by sending
three carriage returns (ENTER key), then send the
6 (csv report), 4
(last data)
command
string just like you might when downloading the data with a computer and a terminal program
as described in Section 9.4. The logger must ignore the BAM menu responses, then receive
the hourly data array response and parse out the desired data parameters and store them
appropriately. The last concentration value, Qtot flow volume, ambient temperature, pressure,
filter RH, and alarm bits are often collected in this manner.
CPU Interruptions:
Care is required when collecting data from the classic BAM 1020 RS-
232 port. The BAM main CPU cannot multitask, so if the BAM 1020 is moving any of the filter
tape or span membrane motors (especially near the top of each hour) it will ignore any RS-
232 serial port commands and interrupt any serial data downloads until the mechanical
motion is complete. See Section 4. The best solution when using the classic RS-232 port is to
program the digital logger to make a single hourly data request to the BAM near the middle of
each hour, such as between minute 25 and minute 50. However, small files such as the last
hourly record can be downloaded very quickly, and may be accomplished at almost any time
during the hour as long as the timing is carefully controlled. If your data logger is programmed
to digitally request data from the BAM 1020 RS-232 port continuously throughout the hour
(such as every minute), then some number of the data requests will certainly be ignored by
the BAM due to mechanical interrupts.
The BX-965 Report Processor back panel option was designed to allow easier digital data
connectivity with the BAM 1020. The REPORT serial port works exactly like the classic RS-
232 port and accesses the same files, except that it has its own CPU and memory and
cannot be interrupted or ignored. The REPORT port also has much more data memory
capacity. The classic RS-232 port
and it’s legacy functionality is also still supported on Report
Processor back panels as a backup.
Clock Timing With Digital Loggers:
Timing must also be considered when collection BAM
data with a digital system. If the BAM is operating in standard cycle mode, then the digital
concentration data values are updated exactly at the top of the hour. If the digital logger is set
to collect the BAM concentration value as soon as it is available, then the clocks should be
synchronized to prevent collecting the wrong hourly record.
If the logger must have the BAM concentration before the top of the hour, then the BAM can
be set for early cycle mode, and the BAM clock will have to be synchronized to the logger.
Some BAM 1020 users leave the BAM in standard cycle mode and set their digital logger to
synchronize the BAM clock at minute 59 of the hour. This causes the BAM to be one minute
ahead of the logger so that the concentration is available at the top of the logger hour. This
method is similar to running in early cycle mode, except the timing schedule is much easier to
understand.
