July 27, 1944

CONFIDENTIAL

Dr. S. S. Prentiss

107 Engineering Building

University of Pennsylvania

Philadelphia 4,

Pennsylvania

Dear Dr. Prentiss:

Under our NDRC contract OEMsr-584 development and construction were started last summer on five Model K Oxygen Meters, which feature the large permanent magnet, and one Modal L Oxygen Meter, otherwise designated as the "airplane model". It was intended that two of the Model K meters be kept here and that the other three Model K meters and the one Model L meter be sent out for such testing and application as might be desired by the NDRC.

The construction of three of the Model K meters and the one Model L meter has been completed. The completion of the two meters which were to remain here has been postponed indefinitely because of the difficulty of obtaining suitable suspensions from the commercial source and because one of the relays which was to be used arrived in a damaged condition and has not yet been replaced. These two meters require only the two suspensions, two calibrated scales, and the one relay for final completion.

Of the three Model K meters which have been completed, two are considered to be satisfactory for sending out. They have respective ranges of 0-45 and 0-85 mm. of oxygen partial pressure. The other meter, which was to be given a range of 95 to 100 percent of one atmosphere of oxygen, has instead a range of 450-760 mm. of oxygen with the 650-760 portion of the range covering about half of the scale. We are not satisfied with this range, which was the best we were able to get with only suspension we could obtain for this type of instrument. We are particularly dissatisfied with the compromising changes we were compelled to make in the meter so that this suspension, some of the characteristics of which were far from those desired, could be used at all.

The Medal L meter has been given a range of 0-186 mm. of oxygen because of the difficulty of obtaining a suspension for the 0-800 mm. range originally intended for this model and because we had on hand a suspension suitable for the former range. This range has the disadvantage of making the meter useless for testing tank oxygen at atmospheric pressure but has the advantage of greater sensitivity over the range corresponding to respirable gas mixtures. The meter has been severely tested on the vibration table. The suspension was not broken in this test but it has been subsequently found that the suspension is poorly balanced, presumably as a result of this very severe test. The meter in its present condition is therefore not satisfactory for airplane use as such an application requires that it give reasonably accurate readings when tipped through large angles.

We are able to ship out any of these meters at the convenience of the NDRC, but we recommend that only two meters, Model K Serial No. 4, with range 0-45 mm., and Model K Serial No. 3, with range 0-85 mm., be made available to any agency for test. I would appreciate it very much if you would advise me as to the desired disposition of these meters. Dr. A. 0. Beckman would probably be interested to undertake further work on the other meters, including the two Model K meters which lack suspensions.

The final report for the oxygen meter project has been written and is now in the process of duplication.

Sincerely yours,

Linus Pauling

LP:jr

cc to E. P. Stevenson

A. O. Beckman