Appendix

Model 356WA

 

 

 

 

or by knowing the altitude

P(mm-Hg) = 760 - (2.50 per 100 ft. of altitude)*

The vapor pressure of water at ambient temperature can be obtained from Table 1.

To determine the corrected flow (Fcorrected), substitute the ambient tem- perature, pressure and vapor pressure of water in the following formula:

Fcorrected

T

 

760 mm Hg

P + P

= 150 cc min × ⎜

 

×

P

×

water

 

294° K * *

 

P

Where:

T = ambient temperature (in °K) P = ambient pressure (in mm Hg)

Pwater = vapor pressure of water at ambient temp. (in mm Hg)

By way of example, suppose that the target’s position on the flow tube is in question and it has been determined that the ambient temperature is 77 °F and the altitude where the instrument is being used is 5000 ft. above sea level.

Ambient Temp: ° K = 5 (77 32) + 273 = 298° K 9

Ambient Pressure: P(mm Hg) = 760 - (2.50 × 50) = 635 mm Hg

Vapor Pressure of Water (at 298° K): 23.9 mm Hg

Corrected Flow: Fcorr = 150 ×

298

 

760

635 + 239.

= 189 cc min

294

×

635

×

635

 

 

 

*This approximation is within ±0.5% of the ICAO Standard Atmo- sphere over the range 0-7500 ft. above sea level. Ref: “Fluid Mechanics for Engineering Technology” by Irving Granet, Prentice Hall, pp 83–84.

**Reference ambient temperature : 294 °K (21 °C) was the ambient temperature used in the Faradaic calculations.

A-6

Teledyne Analytical Instruments

Page 40
Image 40
Teledyne 356WA instruction manual Pmm-Hg = 760 2.50 per 100 ft. of altitude