A number of output pulses linearly related to the logarithm of elapsed time or of input pulse count is generated by a circuit including two counters and a comparator. A fraction 1sol;aof the input pulses is applied to a continuous counter. A second, cycling counter receives all input pulses above a selected starting count, counts to equality with the continuous counter, and resets with production of an output pulse. Repetition of the cycle yields an output pulse series according to the equationtisol;t0equals;asol;(aminus; 1)i, wheretrepresents time or pulse count depending upon the source of pulses, periodic or aperiodic, andiis the number of output pulses. Conformance to the logarithmic relation log (tisol;t0)equals;ilog asol;(aminus; 1) is within 0.01percnt;minus;0.1percnt; for reasonably large input counts. This circuit has been applied to generation of a logarithmic time base for direct linear plotting of data from thermal conductivity measurements of liquids by the transient hothyphen;wire method.
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