The Doble M4000 M4100 Power Factor Insulation Analyzer contains measuring circuits to determine the condition of the insulation under test, as well as direct control safety circuits to ensure electrical safety of personnel and test equipment.The Doble M4100 (Doble M4000) has a time base generator that may be synchronized either with the power system supplying power to the test instrument, or with an internal crystal oscillator. This choice allows the test operator to select one of two modes of test operation, Line Sync Reversal or Line Frequency Modulation.
When Line Sync Reversal Mode is selected, the time base is synchronized to the power source and the test will use the standard Doble polarity reversal technique to reverse the effects of electrostatic interference.
Selecting the Line Frequency Modulation Mode of operation will synchronize the time base generator to the crystal oscillator. Two tests will be run for each programmed test sequence. The first test is run at a frequency of 57 Hz and the second test is run at 63 Hz. The measured test results of each test are combined and averaged to give a 60 Hz equivalent test result. When operating in the 50 Hz frequency, the same technique will apply. The first test will run at 47 Hz, and the second test will run at 53 Hz. This mode of test eliminates electrostatic interference from measurement, by avoiding measurement at power line frequency. It is also possible to select ± 10% of power line frequency as well.
Safety circuits have been designed into the M4000 (M4100) to ensure safety of personnel. High voltage will not be supplied by the instrument if either of the following circuits and conditions are not satisfied:
- The ground safety circuit verifies that the #6 bare copper safety ground is at the same potential as the power supply ground.
- Two safety switches must be attached to the analyzer's front panel and in the closed or depressed position prior to testing.
A safety strobe light can be used in conjunction with the instrument and is plugged into the front panel of the M4100 (M4000).