Geokon 4420, Instruction Manual, Page: 12 / 40

2 | INSTALLATION | GEOKON
2. INSTALLATION
2.1 PRELIMINARY TESTS
Check the gauge for proper operation when you receive it. Check the thermistor
as well. The crackmeter normally arrives with its shaft secured at approximately
50% of its range.
For crackmeters with a range of 100 mm (4") or smaller, the shaft is secured
using a dowel pin held in place by a piece of tape (see Figure 1).
For crackmeters with a range greater than 100 mm, a slotted sleeve made of
PVC secures the shaft.
These devices hold the crackmeter in tension to protect it during shipping. With
the shipping spacers still in place, connect the gauge to a readout box and take
a reading. (See Section 4.1 for readout instructions.) The reading should be
stable and in the range of 4000 to 5000 digits. Please note that crackmeters with
a 3 mm (.125") range are shipped with the push rod fully retracted and have no
shipping spacer to remove. These gauges should read between 2000 to 3000
digits.
Check electrical continuity using an ohmmeter. Be sure to consider the
following:
■
Resistance between the gauge leads should be approximately 180 ohms,
±10 ohms (128 ohms for the Model 4420HT).
■
Remember to add the cable resistance, which is approximately 14.7
Ω
per
1000 ft. (48.5
Ω
per km) of 22 AWG stranded copper leads at 20 °C.
■
Multiply this factor by two to account for both directions.
■
Resistance between the green and white conductors will vary based on
temperature.
■
For standard crackmeters, refer to Table 7 in Appendix B.
■
For the 4420HT crackmeter, refer to Table 8 in Appendix C.
■
Resistance between any conductor and the shield should exceed two
megohms.
Carefully remove the PVC slotted sleeve or dowel pin before proceeding further.
Hold the transducer shaft to prevent it from snapping into the transducer
housing.
2.2 CRACKMETER INSTALLATION
For additional instructions Models 4420HT and 4420-3, see Appendix C and
Appendix E respectively. For additional instructions regarding 3D Arrays, see
Appendix D.
2.2.1 ANCHORS
Three types of anchors are available:
■
Weldable Mounting Fixture
■
Expansion Anchor
■
Groutable Anchor