Campbell Scientific ST350 Strain Transducer for Structural Testing - Manual (Page 25)

Section 7. Maintenance, Replacement
Parts, and Repairs
7.1 Maintenance
The ST350 Strain Transducer has been designed to minimize the amount of
maintenance required to keep the transducers operational. Before each use it is
recommended that every transducer be visually inspected for damage and
powered on to ensure it is working properly. This should be done two to three
weeks before the testing date in case any repairs are required.
Procedure for verifying ST350 is functioning properly
Ensure the Strain Transducer noise is within the specified noise range of the
Data Acquisition Equipment. This can be done by running a short test
(approximately 15-20 seconds) and allowing the sensors to collect data while
not being handled. An example of an output seen for this test can be seen
below in FIGURE 7-1.
FIGURE 7-1. ST350 Strain Transducer Test Output
1. Ensure the Strain Transducer returns a smooth output. Run a test at a
sample frequency higher than 30 Hz and apply a smooth tension force
(gently pulling one each end) followed by a smooth compression force
(gently pushing each end). The output returned should be a tension spike
followed by a compression spike and should not appear “stair-steppy”. An
example of this output can be seen below in FIGURE 7-2.
2. Using the data from #2, ensure the sensor returned to very near zero. In
some cases it may not return exactly to zero due to the sensor being heated
up from being handled and/or not being placed on the work surface in the
same position as it was sitting before being handled. If a significant offset
remains after such a test, this can be an indication of possible damage and
the unit should be sent back.
3. Also, using the data from #2, ensure that the transducer has been
connected to the data acquisition system correctly by ensuring that tension
was registered as positive and compression as negative.
7-1