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3700 Portable Samplers
Appendix E Calculating Flow Increment Between Samples
Sample Volume Considerations – Thus, a sample volume of
188 ml will result in the desired composite sample. Because of
the basic uncertainty of the delivered sample volume exactly
matching the programmed nominal sample volume and the 10 ml
sample repeatability, it is good practice to select a nominal
sample volume which is slightly smaller than the calculated
sample volume. This is to prevent overfilling of the sample con-
tainer. In the example, an individual nominal sample volume of
125 ml might be a prudent choice. For critical applications, cali-
bration of the sample volume can be used. It is important to
select an individual sample volume which will not result in an
overfilled sample container under worst-case conditions.
The nominal volume of the composite sample may be calculated
by multiplying the programmed nominal sample volume by the
total number of samples to be collected. In the example:
125
/
50
= 6,250
ML
SAMPLE X
SAMPLES
ML
This calculated total volume may vary from the actual total
volume because of variations in the actual volume of each indi-
vidual sample. The total time needed to collect the 50 individual
samples may vary from the desired 24 hour period because of
variations in the average flow rate from the 2.5 MGD figure used
in these calculations.
E-3
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