Shift depreciation and internal controls

Our company performs work at the factory on second shift and third shift as per requirement. Sometimes the machine run for upto 3-4 days continiously. After that we require buffering time to change tools, cleaning, etc. In such time, even though machine is not in operation, other assets like computers, ac, etc. are being used. Till today we have been maintaining Manual Register to record daily working hours of the machine. We are calculating shift depreciation on machines as well as other fixed assets at the factory on the basis of working hours (extra shift) of the machines. How can we improve the internal controls for recording the hours of working each day so that the calculation of shift depreciation is true and fair? Are there any computarised systems or procedures? How should we charge depreciation on fixed assets other than machinery which are being used more than the machines?