of the recorder is then disconnected by means of the switch 

 provided for this purpose, and the balancing function is taken 

 over by two sets of similar components in the balancing unito 

 Two sets of the bridge-balancing components are necessary in 

 order to achieve a balance on both gages simultaneously 

 because of the different values of capacitance and dissipation 

 associated with the individual gages. The balancing unit is 

 pictured in Figure j5, with the corresponding schematic 

 diagram in Figure 5° 



PART II 



INSTALLATION, OPERATION* AND MAINTENANCE 



INSTALLATION 



Installation of the Type 286-1A unit is similar to the 

 Type 145-A. The gage is positioned through the resting 

 surface of the water and clamped in this position. Approxi- 

 mately half of the gage should be immersed in the water. The 

 gage is then connected to the wave-height recorder by means 

 of any good quality coaxial cable. As the Type 286-1A is 

 used in the Sanborn console, the connections to the unit 

 are automatically made when the unit is placed in the rack. 

 The connections between the driver amplifier, power supply, 

 and recorder are already made by plug-in cables 4 inside the 

 rack and should offer no problems „ 



Should it be desired to use two gages with a single 

 Type 286-1A unit, a bridge balancing unit, Type 286-2A, may 

 be used to properly couple to the two gages. The internal 

 bridge balancing controls must be switched out of the system 

 by means of the INT-EXT deck switch in the Type 286-lA. The 

 GAGE connector and the two gage cables are then connected 

 to the bridge balancing unit. The functions of the ROUGH 

 CAP BALANCE, CAP. BALANCE, and RES. BALANCE on the Type 286-1 A 

 are then taken over by corresponding controls in the bridge 

 balancing unit. The gages are each balanced in turn in the 

 same manner as described in the next section. It is then 

 possible to record from either gage as desired. 



OPERATION 



Before use, the system should be connected to the power 

 line, turned on and allowed to come to operating temperature. 

 The direct-coupled amplifiers in the system may be expected 

 to drift during this period. A warm-up time of approximately 

 15 minutes should be allowed before measurements are made. 



