Campbell Scientific PST3/PST8 Pump and Slug Test System - Manual (Page 24)

SECTION 4. TECHNICAL DETAILS - HARDWARE
4-3
threshold is 0.25. The units are determined by
the multiplier used for the pressure transducer.
In Delta sampling, measurements are made at
regular intervals. The default sampling interval
is 0.25 seconds. It can be changed in the *4
Table to 0.5 seconds or 1.0 seconds. The
default value gives the greatest resolution.
Example: If the Delta threshold is set to 0.1 feet
and the water level drops 1 foot, 10 data
records would be stored. Each record would
have a time and water level. Each water level
would be approximately 0.1 foot apart and the
time values would correspond to the times when
the water level reached each recorded point.
4.5 MAXIMUM SAMPLING RATES
The maximum recording rate depends on the
number of wells monitored. For Delta tests,
well #1 should be the pumping well; it is
scanned at a faster rate than the monitoring
wells. The following tables show the maximum
rate as a function of the number of wells
monitored for Delta and logarithmic tests.
Well #1 Remaining Wells
Number Maximum Maximum
of Wells Times/sec. Times/sec.
1 4 1
2 4 1
3 3.7 0.9
4 3.5 0.9
5 3 0.9
6 3 0.9
7 2.8 0.7
8 2.8 0.7
Number Maximum
of Wells Times/sec.
1 4
2 4
3 2
4 2
5 2
6 2
7 1.5
8 1.5
4.5.1 OVERRUN
A table overrun occurs when the program is not
completed within the time of the execution
interval. In the Delta mode table overruns
occur, so don't be concerned. The four times
per second execution interval is set up to
optimize speed of data collection. If an overrun
occurs the program executes at the next 0.25
second interval.
4.6. DATA STORAGE CAPACITY
Water level values less than 69 use one data
point per well while values over 69 use two data
points. The examples found in Sections 4.6.1
and 4.6.3 assume level values less than 69
using only one data point.
4.6.1 DELTA WITH ELAPSED TIME
Delta files with elapsed time use three data
points (well #, time, and level < 69) in Final
Storage each time a recording is made. With
29,900 available data points in Final Storage,
9967 recordings (29,900/3) can be made before
data are overwritten. The time it takes before
the oldest data are overwritten with new data is
dependent on the Delta interval and the total
change in depth of all the wells.
Example: If there is one well, a Delta value of
0.05 feet, and the well level changes 100 feet
during the test, then there will be a total of 2000
(100 ft / 0.05 ft/record = 2000 records)
recordings of time and the corresponding level
out of the 9967 possible. There would still be
7967 recordings remaining before the oldest
data is overwritten. If there are six wells and
the total water level change of all wells
combined is 100 feet, with the same Delta value
of 0.05 feet, 2000 of the possible 9967
recordings would still be used.
4.6.2 DELTA WITH CLOCK TIME
Delta files with clock time use five data points in
Final Storage each time a recording is made.
With 29,900 available data points in Final
Storage, 5980 recordings can be made before
data are overwritten. The previous example for
lapsed time holds except that total number of
recordings is 5980.
4.6.3 LOGARITHMIC WITH ELAPSED
TIME
Memory overwriting is dependent on the time
and the number of wells. One well uses three
data points each time a recording is made; two
wells use four data points; eight wells use 10
data points. Figure the total number of
recordings that can be stored by dividing 29,900