User's Manual

®
Hydraulics Structures Set Adding Load Cells
6
Using a Liquid Instead of a Gas
Fill a syringe with a liquid. Connect the syringe to the syringe
coupler. Push the piston slowly to force liquid from the
syringe into the syringe coupler until all the air is pushed out
of the coupler. Finally, connect a second syringe (or the
hydraulic cylinder) with the piston all the way in to the liquid
filled syringe coupler. When you push on the piston of the liq-
uid filled syringe, the liquid will push against the piston of the
second syringe (or cylinder).
CAUTION: If you use the Pressure Sensor Coupler and a
pressure sensor in your hydraulics structure, be sure that no
liquid enters the pressure port of the sensor. Liquid can go partway into the tubing of the Pressure Sensor Coupler
where it connects to the sensor, but leave an air space in the tubing between the liquid and the sensor.
Using a Rotary Motion Sensor to Measure Volume
You can mount a Rotary Motion Sensor (PS-2120) on a rod and attach the rod to your hydraulics structure using
Structures Rod Clamps* (ME-6986). Please see the illustration of the Hydraulic Boom on page 8. Use a thumb-
screw to secure a Drive Wheel* to an axle that will turn when a part of the structure moves. Arrange the sensor and
drive wheel so that the included O-ring will fit over the drive wheel and the largest pulley on the sensor.
Use the data acquisition software to calibrate the Rotary Motion Sensor. Set the structure so that the volume in the
hydraulic cylinder is zero. In the software, set the corresponding position of the Rotary Motion Sensor to be 0 mL
(zero milliliters). Move the structure so that the volume in the hydraulic cylinder is at its maximum. Set the corre-
sponding position of the Rotary Motion Sensor to be the maximum volume (e.g., 60 mL).
Adding Load Cells
To measure the compression and tension forces in indi-
vidual members of a structure, add load cells (e.g.,
PASCO Model PS-2200 or PS-2201) to any PASCO
Structure. Replace a beam with two shorter beams and a
load cell.
#5 beam = load cell + two #3 beams
#4 beam = load cell + two #2 beams
#3 beam = load cell + two #1 beams
Use thumbscrews to attach two beams to a load cell as shown in the figure.
When using load cells, assemble your structure with the screws loose. This
will simplify the analysis by ensuring that the members experience only ten-
sion and compression without moments.
Calibration
See the instructions that came with the load cells for details about how to con-
nect the load cells to an interface or datalogger. Follow the instructions to cali-
brate the load cells and use them to collect data. (Load cells are factory
calibrated; however, you can re-calibrate them in software or on the datalog-
ger. See the documentation for your software or datalogger for instructions.)
Leave an air space
between the liquid
and the sensor
Air space
Liquid
Figure 9: Air Space
Figure 10: A load cell combined with two #2 beams is
the same length as a #4 beam
Figure 11:
Calibration fixture
*Included in the
Advanced
Structures Set.