The measurement of moisture concentration in cable insulation

The results of measurement of the moisture content of XLPE cable insulation obtained from a DuPont model 903 Moisture Evolution Analyzer often disagrees with the results of the same measurements made with a Mitsubishi Moisture Meter by as much as a factor of two. The former instrument uses a cell containing P2O5 as its active element, and the latter performs an automated Karl Fisher titration. The two instruments were calibrated using the water hydration of sodium tartrate as a standard. Moisture measurements made as a function of the oven temperature for both instruments were in good agreement with weight loss measurements made by thermogravimetric analysis of the sodium tartrate. These results and others have shown that the accuracy and precision of both instruments are within ± 1% for the measurement of amounts of water of the order of 1000 micrograms. The present results show that the lack of agreement among the measurements can be explained as the result of interference by such volatile substances as acetophenone and cumyl alcohol.