CHAPTER F 



A-SHEET COMPUTATIONS 



F-1 General. — A-Sheet computations include 

 correcting protected thermometer readings, 

 averaging water temperatures, correcting un- 

 protected thermometer readings, calculating 

 thermometric depths, and determining accepted 

 depths. To perform these calculations, the Re- 

 versing Thermometer Calibration and History 

 Record PRNC-NAVOCEANO-3167/53 (Rev. 

 2-64) for each thermometer used is required, 

 and an L-Z Graph NAVOCEANO 3167/62 

 (Rev. 2-64) for each cast of the oceanographic 

 station is required. The A-Sheet is described 

 in chapter E. 



F-2 Reversing Thermometer Calibration 

 and History Record. — After a deep sea revers- 

 ing thermometer is manufactured and before it 

 is used in taking an oceanographic station, the 

 thermometer must be calibrated. This calibra- 

 tion process determines the deep sea reversing 

 thermometer corrections to be applied to the 

 temperature scales etched on the main and aux- 

 iliary stems of the thermometers. It also estab- 

 lishes the volume of mercury (Vo), at zero 

 degrees Centigrade, in the thermometer reser- 

 voir and main stem capillp,ry. In addition, the 

 calibration determines the "Q" Factor, or pres- 

 sure factor, for unprotected thermometers at 

 1,000-, 2,000-, 3,000-meter, etc., depth increments. 

 "Q" Factors for 500-meter depth increments 

 are determined when required. Thermometers 

 are calibrated at the U.S. Naval Oceanographic 

 Instrumentation Center, and the results are re- 

 corded on the Reversing Thermometer Calibra- 

 tion and Histoi-y Record (fig. F-1). The record 

 includes the following information : The ther- 

 mometer number, make (manufacturer's name) , 

 Vo in °C., makers Vo in °C., "K" value (glass- 

 mercury coefficient of expansion constant), 

 range (main stem scale), smallest scale divi- 

 sion, protected or unprotected, owner, purchased 

 new or used, purchased from, cost, and date 

 acquired. In addition, the record includes Deep 

 Sea Reversing Thermometer Corrections at 

 various temperatures for both main and aux- 

 iliary thermometers and "Q" factors for unpro- 

 tected thermometers. The record also includes 

 an interpolation table for temperature correc- 

 tions. This table is completed by the thermom- 

 eter user. Instrumentation personnel perform- 

 ing and certifying the calibration, the date 

 calibrated, the adherence to contract specifica- 



tions, and the functioning of the instrument are 

 shown on the record. The bottom of the form 

 contains a Thermometer History Record for 

 the user to record cruise, dates thermometer was 

 used, and performance (see ch. G). 



F-3 The Main and Auxiliary Interpolation 

 Table,— The values for tlie Main and Auxiliary 

 Interpolation Tables can be computed graphi- 

 cally or algebraically as follows: 



( 1 ) Graphically : 



Step 1. Construct a graph making the main 

 thermometer correction as one coordinate and 

 the main thermometer temperature as the other 

 (fig. F-2). 



Step 2. At the plus and minus 0.005, 0.015, 

 0.025, etc., correction values, determine the cor- 

 responding temperature, and enter the values 

 in the Mam Interpolation Table (round to the 

 nearest hundredth degree). 



Step 3. Construct a similar graph for the 

 auxiliary corrections and temperatures and de- 

 termine the plus and minus 0.05, 0.15, 0.25, etc., 

 correction values and enter in the Auxiliary 

 Interpolation Table (round to the nearest tenth 

 degree) . 



(2) Algebraically: 



Step 1. Compute the temperatures (Tc) that 

 correspond to the "I" (Ic) by the following 

 formula : 



T-.-Tx _ Tc-Ti 



C2-C1 Ic-Ci 



where Ic is plus or minus 0.005, 0.015, 0.025, etc., 

 correction values and Ti and To and Ci and C2 

 are the thermometer main temperatures and 

 corrections on the calibration card. 



Example : 

 5-0 



Tc-0 



+ 0.011- (-0.002) -t-0.005-( -0.002) 

 10-5 Te-5 



Tc = 2.69 



Tc = 6.18 



+ 0.028- (+0.011) +0.015- (+0.011) 



Step 2. Round Ic to hundredth in direction of 

 Cx and enter in the Main Interpolation Table. 



Step 3. Repeat step 1 substituting plus or 

 minus 0.05, 0.15, 0.25, etc., correction values Ic, 

 and the auxiliary temperatures and corrections 

 for Ti and T, and Ci and C3. 



Step 4. Round Ic to tenth in direction of Ci 

 and enter in the Auxiliary Interpolation Table. 



F-1 



223-812 0-68-5 



