V O L U M E 20, NO. 12, D E C E M B E R 1 9 4 8
1237
Table 11. Characteristics of Radioactive Microbalance Characteristics sensitivity Period Reproducibility
Stability Humidity Temwrature sensiti*ty change nith load,
.
Type A, Low Center of Gravity. 1 Mg. i Type B, High Center of G r a ~ t y 1 0.1 to 0.4 Mm. Mg. = 2 to 5 M m L Eleatrid Mechanical Eliotrieal Mechanical 2 x lo-l~arnpere 0 . 0 1 to 1 microgram 3 x 10-10hrnpere Imiorogr&mtoO.l mg. 2 to 4 seconds 10 to30 reconde 2 to 4 seconds 1 to 2 minutes Good (1 to 6 rnioropraml Good Chhngea with average error with present beam and pan arrestment system
Good No effect N o effect
...
Dbmping
...
Load owseity
...
Good
1 to 5%
... ...
Magnetio or none at SI1 50 gram per pa"
Good No effect No effeot
...
...
...
were parallel with the left t o right line of disolacement of the radioactive foil. CHARACTERISTICS O F RADIOACTIVE
:
the sensitivity changes greatly with increasing load. Improvements are being made in the ahove characteristics and additional data. are being compiled. It has been possible to determine the
mechanical errors and limitations of the balance through radioactive displacement measurements, as well as through the utilization of capacitance, inducchanges with load ... tance, optical systems, ete. (f,6). These 30 to 7;% have taken the form of measurement of linear displacements on the order of 0.1 M*.neti0 micron; rncasuremcnt of angular d i c 20 grams per pan placements 0.005' to 0.0001 '; linear, solid distortion, and compression measurcmentsc.g., measurement of flexure of beams; and vibration measurements. In the course of the research on the heavy centered radioactive microbalance a number of new testing and measuring instruments were developed because of thc necessity of performing extremely fine displacement measurements. These include an angle measuring 8. tilt and compression meter, a vibration meter, and air convection current meter. In radioactive instrumentation one possesses a tool that has virtually unlimited research and industrial possibilities and the radioactive balance is hut one example of the application of radioactive instrumentation to science and industry.
Table I1 gives characteristics of the ritdioarr,vr , , , , ~ , u u ~ , I I , , ~ l i , Types A and B. The radioactive mierohblance has the advantages of high sensitivity, external control of sensitivity, constsney of sensi. tivity under increasing load, stability ,f sensitivity, external method of calibrating fine nreights, extrelnely short nreighing periods possible (Type A), external electrical reading device ACKNOWLEDGMENT which can be read easily, large load capacity, and measurement of various balance errors instantaneously and directly. Control The author wishes to thank H. K. Alher, Arthur h. lnomas and weight limiting can he adapted radioactively for fast approxiCompany, Philadelphia, Pa.; A. H. Corwin, Department of
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