In-Situ TROLL 9500 Operators Manual User Manual
Page 151
146
0095110 rev. 007 01/09
TROLL 9500 Operator’s Manual
g x (L
2
- L
1
)
(P
2
– P
1
) x 6.894757
R
Note: Density can also be measured using a hydrometer if it is pos-
sible to withdraw a water sample from the well. We recommend an
accuracy of ±0.0005.
Procedure
There are two possible methods for measuring the change in water
depth. Choose the method that is the most convenient and accurate.
s
(e.g., duct tape). The tape measure can be attached to the trans-
ducer itself or to a segment of the cable that will be adjacent to the
top of the well casing. Read the cable positions directly from the
measuring tape. The measuring device must have a resolution of
at least 1 mm or 1/16 in.
s
tip pen. The distance between marks is then determined with a
tape measure after the corresponding cable segment is removed
from the well.
1. Lower the transducer into the well until it is submerged under about
one meter of water.
2. Secure the transducer at a fixed depth using the cable at the top of
the well casing. Wait an hour or so for the system to equilibrate.
3. Take an electronic pressure reading, manually, from the transducer
and record this measurement in PSI. This is measurement P
1
.
4. Read the tape measure relative to some fixed reference point (e.g.,
top of well casing) or mark the position on the cable with an indel-
ible pen. This is measurement L
1
.
5. Lower the transducer at least three meters deeper into the water
and repeat steps 3 and 4. These are measurements P
2
and L
2
.
6. Density (R) in g/cm
3
is calculated using the following:
where g is the gravitational acceleration for the location of the well
in m/s
2
. P must be in PSI units and L must be in meters. If using a
tape measure calibrated in feet, 1 ft = 0.3048 m (exactly).
An error of 0.001 m (1 mm) in the depth measurement
translates into an error of 0.00085 g/cm
3
for density.
APPENDIX