Different Types of Earth Pressure Cells, Their Applications and Construction of Isobar Diagram Using Them-19

2.15 Electrical Noise

Care should be exercised when installing instrument cables to keep them as far away as possible from sources of electrical interference such as power lines, generators, motors, transformers, arc welders, etc. Cables should never be buried or run with AC power lines. The instrument cables will pick up the 50 or 60 Hz (or other frequency) noise from the power cable and this will likely cause a problem obtaining a stable reading.

2.16 Initial Readings

Initial readings must be taken and carefully recorded along with the barometric pressure and temperature at the time of installation. The initial readings should be taken while the cell is in position, just prior to it being covered by fill and pouring of concrete. Again, it is imperative that initial readings at zero load are taken.

2.17 TAKING READINGS

Operation of the GK-403 Readout Box

The GK-403 can store gage readings and also apply calibration factors to convert readings to engineering units. The following instructions will explain taking gage measurements using Mode "B".

Fig. 2.13. G K- 403 Front Panel.

Readout is connected using the flying leads or in the case of a terminal station, with a connector. The red and black clips are for the vibrating wire gage, the white and green clips are for the thermistor and the blue for the shield drain wire.

1. The Readout is turned on. The display is positioned to mode "B". Readout is in digits.

2. The unit is turned on and a reading will appear in the front display window. The last digit may change one or two digits while reading. The "Store" button is pressed to record the value displayed. The thermistor will be read and output directly in degrees centigrade.

3. The unit will automatically turn itself off after approximately 2 minutes to conserve power.