to- 0.1 C over the temperature range on a standardized R-T 

 curve. Furthermore, it has a stability of 0. 05°C per year maximum 

 change, and extremely fast time of response. In order to permit 

 a low sampling and data storage rate, the temperature sensing time 

 constant is increased to 60 seconds by insulating the sensor from 

 the sea water and thermally coupling it to the relatively massive 

 sensor housing. At the nominal operating temperature of 11°C, 

 the thermistor resistance is 200 K ohms and its scale factor is 

 10 K ohms per °C, Since the bridge resolution at 200 K ohms is 

 80 ohms, we have no difficulty in achieving the desired temperature 

 resolution of . 01°C. 



3.2.3 Pressure Sensors 



At the 700 meter array depth the pressure is approximately 

 700 decibars, or 1040 PSI. 



The pressure transducer selected is manufactured by Sparton 

 Southwest, Inc. as Type 890-A-200-450 which employs a Bourdon 

 tube connected to a potentiometer. It has a pressure range of 0-2000 

 PSI and a resolution of 2 PSI. Absolute accuracy is approximately 

 1%. The scale factor is approximately 20 ohms /PSI. The time 

 constant is approximately 0. 1 second. 



3.2.4 Tensiometer 



Because a suitable off-the-shelf tensiometer could not be ob- 

 tained for the available funds, we built our own. Figure 3-16 con- 

 tains an incomplete but adequate drawing of the unit. The tension 

 sensing element is the end plate of Station 4 which deforms as a 

 diaphram under load. A hydraulic amplification of diaphram dis- 

 placement is accomplished by the trapped fluid and bellows arrange- 

 ment. The bellows in turn is connected to a linear potentiometer 

 which provides a resistance output compatible with the over-all 

 dc bridge measurement scheme. The unit is clearly temperature 

 and pressure sensitive, so that its output must be combined with 

 the pressure and temperature outputs at Station 4 to determine 

 tension from the formula 



R = K + K T + K^ W + K, P 

 o 1 2 3 



212 



