Geokon 4425, Instruction Manual, Page: 8 / 27

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2. INSTALLATION
2.1 Preliminary Tests
Upon receipt of the instrument, the gauge should be checked for proper operation (including the
thermistor). See Section 3 for readout instructions. In position “B” the gauge will read around
2000 when the threaded connector is pulled out approximately 3 mm (0.125").
Figure 2 - Operation Check
CAUTION! Do not extend the connector more than the range of the gauge. Do not turn the
threaded shaft at the end of the gauge more than 180 degrees or gauge failure may occur!
Checks of electrical continuity can also be made using an ohmmeter. Resistance between the
gauge leads (red and black) should be approximately 180 Ω , ±10 Ω . Resistance between the
thermistor leads (white and green) varies with temperature; see Appendix B. Resistance between
any conductor and the shield should exceed two megohms. (For long cables a correction can be
applied, equal to approximately 14.7 Ω per one thousand feet [ 48.5Ω per km ] of 22 AWG
stranded copper leads. Multiply this factor by two to account for both directions.)
2.2 Convergence Meter Installation
1) The first step is to unpack all the various components and lay them on a flat surface in their
relative positions. (Refer to Figure 1 in Section 1.)
2) Next, the two anchor points must be installed. When the locations have been decided, drill
holes to accommodate the anchors. Cement the eyebolt anchors in place using quick-set
(hydraulic) cement or epoxy. Allow the cement or epoxy to set completely before attempting
the installation of the convergence meter.
3) Attach the turnbuckle assembly to the convergence meter by screwing in the left-hand
threaded portion. Use thread locking cement and tighten the lock nut. Set the turnbuckle such
that about 10-12 mm (0.5") of thread is inside from each end
.
4) Measure the total distance from anchor eyebolt to anchor eyebolt, inside to inside at the
points where they will touch the convergence meter eyehooks.
5) Check and confirm the convergence meter length against the length shown in Table 1. The
measurement is made from inside the eyehooks (at the point where they touch the anchor
eyebolts), to the end of the Swagelok fitting. To calculate the rod length that will be needed,
subtract the convergence meter length from the anchor eyebolt to anchor eyebolt distance,