Dynamic values always changed and cannot be observed repetitively which led to the measurement uncertainty were hard to be evaluated. To solve the problem, dynamic values were mapped into constants with an algorithm derived in this paper so that repeated observation can be realized. It was analyzed in this paper that the effect of assumptions, parameters on the algorithm evolution results, and the influence of uncertainty of dynamic values on the reproducibility of a signal. Simulation was completed in MATLAB, which illustrated the effectiveness of the mapping constant algorithm (MCA) in evaluation of uncertainty for typical dynamic values. The actual data from a recorder was analyzed to verify the practicability of the MCA. The MCA can be used in evaluation of uncertainty of recorders or any other devices based on samples.