ISCO 6700SR, Instruction Manual, Page: 97 / 190

6700SR Refrigerated Sampler
79
Pacing
Sample pacing is the rate at which the sampler takes -samples.
Depending on the type of pacing you select, the rate is controlled
by the sampler’s internal clock or by inputs received from connect-
ed instruments.
Standard programming provides time pacing and flow pacing. Ex-
tended programming provides additional pacing types: random in-
terval pacing, nonuniform-time pacing and event pacing.
In time-paced sampling, the interval between samples is a constant
time interval. When you program the sampler for time pacing, the
sampler prompts you to enter the time between sample events in
hours and minutes (screen
5 ). The sampler always takes a sample
at the start time.
Flow paced sampling requires a flow meter, flow logger, or a module.
A flow meter or flow logger paces a sampler by sending an electronic
signal to the sampler after measuring a specified volume of liquid.
Because each pulse represents a volume interval, flow pacing rates
are proportional to the volume of water flowing through the channel.
When you program the sampler for flow pacing and are using a flow
meter or flow logger, the sampler prompts you to enter the interval
between sample events in pulses. (See screen
6. ) The sampler ini-
tiates a sample event when the set number of pulses is received.
Standard programs that are flow paced do not take a sample at the
start time. Extended programs have a SAMPLE AT START? option.
The flow pacing screens change when you attach a flow module. Be-
cause the sampler is more closely integrated with the modules, the
standard flow pacing screen prompts you for the flow volume be-
tween sample events instead of pulses between events (screen
7 ).
The flow volume units displayed are what you had previously pro-
grammed. When using extended programming, you are able to
choose the source of the flow pacing. The “PACED BY:” screen lists
both options. Select “FLOW PULSES” for an external flow meter,
“FLOW MODULE VOLUME” for the module.
Trigger Pacing
Isco 4200 Series Flow Meters and 4100 Series Flow Loggers send
pulses for trigger pacing. The flow meter or flow logger sends puls-
es at two different time intervals when trigger pacing a sampler.
Trigger pacing, for example, lets you sample less frequently when
the trigger condition - level, flow, or rainfall - remains below a set
point. The intervals are determined by the flow instrument’s pro-
gram settings for trigger pacing.
When conditions change and readings pass the set point, triggering
the new rate, you can sample more frequently. Or, when the trigger
condition is a clock setting, the instrument changes the pacing inter-
val according to the time of day. Using a clock trigger condition, for
instance, the flow meter or flow logger can pace the sampler slowly
at night and more frequently during the day. (For more information
about trigger pacing, see your flow meter or Flowlink manual.)
The flow meter or flow logger sends the same pulse for both flow
and trigger pacing, and the sampler cannot distinguish between
them. Therefore, to program a sampler for trigger pacing, simply
program it for flow pacing.
Screen Charts for Pacing
Figure 23, Standard
Programming: Programming
Screens on page 108.
Figure 25, Standard
Programming: Quick View;
Programming Screens on page
110.
Figure 34, Extended
Programming: Pacing and
Distribution on page 118.
Figure 38, Extended
Programming: Quick View;
Pacing and Distribution on page
122.
Standard Time Pacing and
Flow Pacing Screens for
Samplers without Flow
Modules
Flow Pacing Screen for
Samplers with
Flow Modules
5
TIME BETWEEN
SAMPLE EVENTS:
__ HOURS, __ MINUTES
6
FLOW BETWEEN
SAMPLE EVENTS:
____ PULSES (1-9999)
7
FLOW BETWEEN
SAMPLE EVENTS:
____ Mgal
(0.001 --99999)