The paper has analyazed the two kinds of errors in measurement of hydrogen humidityby psychrometer DHM - 2 in domestic power station at present. One is system error frompsychrometer defect, other is random error from non-steady hydrogen velocity in measurement. Psychrometer DHM - 2 is improved in order to dispelling these errors. The seleevesisolated air and heat are used, device determined hydrogen velocity is added. The resultsof practical measurement in power station show that relative error of hydrogen absolute humidity by improved psychrometer is decreased from original about 40% to less than 5%, thesteady and precision of measurement are greatly increased.
