Magnitudes of strain-gaging errors

Conclusions

Table 1 indicates that the drift of most types of strain indicator available in our laboratory was fairly small. The drift of the Ellis BAM-1 could have been greatly reduced by re-setting the calibration periodically as was done on one run using the Nosker instrument. Table 2 indicates that the variations introduced by all the coupling and switching devices, with the exception of the Cinch-Jones 300 series plugs, was practically negligible, even when expressed in the units in which we are accustomed to measure—microinches per inch. In conclusion, it should be noted that lubrication decreased the magnitude of variation in all the auxiliary equipment except for the new rotary switches, but that even in this exception it did not increase the amount of variation. A T.V. and radio tuner lubricant, of which Walsco Tunerlub is one example, should be used whenever possible on auxiliary equipment such as switches, plugs and receptacles, and terminal strips whenever these are used in electrical-resistance strain-gage circuits. These lubricants, under a variety of trade names (some being combined with a cleaner), are available at most T.V. and radio supply companies.