Correction of ratemeter output in water content measurements using gamma ray absorption

In an earlier paper presented at the second conference of the Australian Road Research Board the general instrumentation requirements for laboratory determinations of rapidly changing moisture contents using gamma ray absorption were discussed. The present paper forms a continuation of the previous study and emphasizes the necessary response correction procedures. The response characteristics of ratemeters are discussed and the relevant response theory presented, together with a description and tabulation of the 'unit error function'. An experimental method for determining the time constant variation with meter reading is detailed and the correction procedure necessary in determining the true input from a recorded output for this case illustrated. Finally, the procedure is applied to ratemeter readings taken during water content measurements on a draining sand column (a).