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3700 Portable Samplers
Section 3 Programming Guidelines
3.3 Types of Sampling
Available in Extended
Programming Mode
3.3.1 Nonuniform Time
Intervals
3.3.2 Extended Multiplexing
3-6
The extended programming mode expands the variations of
sample pacing and distribution. The extended features listed
below are used in more complex sampling routines. Note,
however, that the sampling capabilities described in Section 3.2
are available in both the basic and the extended programming
modes. Note also that STORM programming is available only in
the extended programming mode.
In the extended programming mode, the 3700 Sampler can pace
samples at nonuniform time intervals. With nonuniform time
intervals, the 3700 takes samples at irregular intervals, rather
than at equal intervals.
Nonuniform time intervals are typically used in runoff studies,
often in conjunction with an Isco 1640 Liquid Level Actuator.
Nonuniform time intervals let you collect a number of samples at
short intervals after a rainfall or other event occurs and collect
remaining samples at widening intervals. For example, when you
use the sampler with the actuator in a runoff study, the actuator
turns on the sampler when the liquid level of the flow stream
rises to contact the actuator's probe. With nonuniform time
intervals, the sampler can collect samples frequently when the
flow rate is highest and less frequently as the flow rate
decreases.
You can also use nonuniform times to simulate flow-paced sam-
pling. When the flow rate varies predictably, using nonuniform
time intervals allows you to take samples at equal flow volumes.
As the flow rate increases, you can take samples at equal flow
volumes by decreasing the time interval. As the flow rate
decreases, you can increase the time interval.
When you use nonuniform times, the time interval between each
sample event is programmable. You can enter nonuniform times
in two ways: in minutes or in clock times. The first method,
minutes, allows you to enter the number of sample events spaced
at intervals defined in minutes: 12 samples at 5-minute
intervals, six samples at 10-minute intervals, four samples at
15-minute intervals, and so on.
You can also enter a specific clock time and date for each sample
event: sample event 1 at 6:00 on April 20, sample event 2 at 6:30
on April 20, sample event 3 at 7:15 on April 20. You can specify
as many as 999 sample events spaced in nonuniform minutes, or
as many as 99 events as clock times. (If a routine requires a large
number of nonuniform times, you can save the routine with the
program storage feature so that you do not have to reenter the
nonuniform times.) You can use nonuniform time intervals with
sequential, multiplexed, and composite sampling.
Multiplexing is somewhat more flexible in the extended pro-
graming mode than in the basic mode. In the extended mode, you
can switch multiplexed bottles or bottle sets after a programmed
number of samples have been deposited, or after a programmed
period of time has elapsed. Under most conditions, we rec-
ommend you switch bottles or sets after collecting a programmed
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