TROLL 9500 Operator's Manual - Geotech Environmental Equipment

AppendixNote: Density can also be measured using a hydrometer if it is possibleto withdraw a water sample from the well. We recommend anaccuracy of ±0.0005.ProcedureThere are two possible methods for measuring the change in waterdepth. Choose the method that is the most convenient and accurate.• Attach the tape measure to the transducer cable using an adhesive(e.g., duct tape). The tape measure can be attached to the transduceritself or to a segment of the cable that will be adjacent to thetop of the well casing. Read the cable positions directly from themeasuring tape. The measuring device must have a resolution ofat least 1 mm or 1/16 in.• Alternatively, mark the positions of the cable with an indelible felttip pen. The distance between marks is then determined with atape measure after the corresponding cable segment is removedfrom the well.1. Lower the transducer into the well until it is submerged under aboutone meter of water.3. Take an electronic pressure reading, manually, from the transducerand 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 indeliblepen. This is measurement L 1.5. Lower the transducer at least three meters deeper into the waterand repeat steps 3 and 4. These are measurements P 2and L 2.6. Density (ρ) in g/cm 3 is calculated using the following:ρ =(P 2– P 1) x 6.894757g x (L 2- L 1)where g is the gravitational acceleration for the location of the wellin m/s 2 . P must be in PSI units and L must be in meters. If using atape measure calibrated in feet, 1 ft = 0.3048 m (exactly).An error of 0.001 m (1 mm) in the depth measurementtranslates into an error of 0.00085 g/cm 3 for density.2. Secure the transducer at a fixed depth using the cable at the top ofthe well casing. Wait an hour or so for the system to equilibrate.TROLL 9500 Operator’s Manual146 0095110 rev. 007 01/09