Geokon 1300, Instruction Manual

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3.3. Operation of the GK404 Readout Box
The GK404 is a palm sized readout box which diplays the Vibrating wire value and the
temperature in degrees centigrade.
The GK-404 Vibrating Wire Readout arrives with a patch cord for connecting to the vibrating
wire gages. One end will consist of a 5-pin plug for connecting to the respective socket on the
bottom of the GK-404 enclosure. The other end will consist of 5 leads terminated with alligator
clips. Note the colors of the alligator clips are red, black, green, white and blue. The colors
represent the positive vibrating wire gage lead (red), negative vibrating wire gage lead (black),
positive thermistor lead (green), negative thermistor lead (white) and transducer cable drain wire
(blue). The clips should be connected to their respectively colored leads from the vibrating wire
gage cable.
Use the
POS (Position) button to select position B and the MODE button to select Dg, (digits).
Other functions can be selected as described in the GK404 Manual.
The GK-404 will continue to take measurements and display the readings until the OFF button is
pushed, or if enabled, when the automatic Power-Off timer shuts the GK-404 off.
The GK-404 continuously monitors the status of the (2) 1.5V AA cells, and when their combined
voltage drops to 2V, the message
Batteries Low is displayed on the screen. A fresh set of 1.5V
AA batteries should be installed at this point
3.4. Measuring Temperatures
The vibrating wire transducers used in the Model A-9 Retrievable Extensometer is equipped with
a thermistor for reading temperature. The thermistor gives a varying resistance output as the
temperature changes. Usually the white and green leads are connected to the internal thermistor.
1. Connect an ohmmeter to the two thermistor leads coming from the transducer. (Since the
resistance changes with temperature are so large, the effect of cable resistance is usually
insignificant.)
2. Look up the temperature for the measured resistance in Table B-1 (Appendix B). Alternately
the temperature could be calculated using Equation B-1 (Appendix B). For example, a
resistance of 3400 ohms equivalent to 22° C. When long cables are used the cable resistance
may need to be taken into account. Standard 22 AWG stranded copper lead cable is
approximately 14.7

/1000' or 48.5

/km, multiply by 2 for both directions.
Note: The GK-403 and GK-404 readout boxes will read the thermistor and display temperature
in

C automatically.