Campbell Scientific ST350 Strain Transducer for Structural Testing - Manual (Page 19)

Section 5. Mounting of Sensor to Various Surfaces
- Slide the drilling jig over the stud and align it with the second
hole location.
- Drill the second 1/4” hole and follow the previous steps for
securing the second concrete anchor.
- Remove the washers and nut from this stud.
- Slide the transducer end over the stud without washers and the
extension end over the one with washers.
- While holding the transducer assembly in place, screw nuts on the
studs and tighten with an open-end wrench.
3. Installation method for best measurements:
The method of gluing both tabs has been used for many years with very
few problems. The main concern is having a clean, dust free surface for
the glue to stick to. Occasionally the bottom of a slab may be wet or
excessively rough, or the sensors must stay in place for over a couple of
days, necessitating the use of mounting studs. Another consideration is if
the structure has automobile or other traffic below it, it is always a good
idea to use the studs on at least one end.
- Using two threaded studs is the most secure way to attach a
transducer to an R/C structure, but it is considerably more time-
consuming and the accuracy of the marking and hole drilling is
significantly more important. If the area is difficult to access, the
transducers are going to be installed for an extended period of time,
or it is imperative that the measurements be taken at a specific time,
using two threaded studs is highly recommended.
- If the transducers are only going to be used for one day tab/glue is
likely sufficient. If the transducer is going to be installed for two to
four days the tab/glue + threaded stud is likely acceptable, but
depends on the climate and concrete condition. In areas of high
humidity the concrete tends to have higher moisture content. This
moisture builds up behind the glue tab and in some cases can cause
the tab to “pop” off.
4. Pitfalls to avoid during installation:
- If the Tab/Glue method is being used, ensure that the area is clean of
dust before installing the gage. A can of compressed air or an air
compressor is a great way to ensure a dust-free gluing area.
- If two threaded studs are going to be used, a drilling jig should be
fabricated to properly locate the hole positions. The transducer does
have an oval hole to help compensate for a hole being miss-drilled,
but as the gage length increases, the variability in the alignment
increases too.
- If the mounting surface is not flat or there are obstructions in the way
of the extension, the obstruction may have to be chipped/ground or
the mounting surface may need to be flattened with a grinder.
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