BAM 1020-9800 Manual Rev W.docx
Page 75
8.2 Early Cycle Mode Option For Analog Data Collection
During a standard BAM 1020 measurement cycle, the BAM 1020 waits for the beginning of
the new hour before it sets the analog output to represent the just-
finished hour’s
concentration. However, some types of data loggers must have the concentration value
available
before
the new hour starts, or the data will be stored in the wrong hour. The BAM
1020 has a special EARLY cycle mode (in the SETUP > INTERFACE menu) which causes
the BAM 1020 to start and finish the measurement a few minutes early in order to output the
concentration voltage for the last 5-minutes of the hour which was just sampled. The data
logger must be programmed to read this value during the window. Because of the critical
timing involved, the BAM 1020 clock will have to be synchronized to the data logger clock
using the EXT RESET inputs described below. The following describes the timing of the
STANDARD and EARLY modes.
STANDARD Cycle Example
EARLY Cycle Example
Analog Output Levels
C
0
represents the concentration output level measured from time
T
0
to
T
1
, where the T labels
represent the top (beginning) of an hour (such as 12:00:00). As you can see, the
concentration voltage
C
0
for the standard cycle is present for the whole next hour following
the measurement. In early mode, the
C
0
voltage for the current hour is present for only the
last 5 minutes of the hour just-sampled (minute 55 to 60), and all other times the
concentration output voltage is fixed at 0.920 volts.
External Reset Windows
An external reset signal may be used to synchronize the BAM 1020 clock to the data logger.
In standard mode the external reset window is plus or minus 5 minutes around the beginning
of the hour, but in early mode the external reset window is between minute 50 and 60 only.
The BAM clock will not reset if the previous cycle has not finished the I
3
count
, and an “E”
alarm will be logged. See Section 7.2.
