Fluke 787 Measuring Electrical Parameters, Input Impedance, Ranges, Measuring a Composite Signal

ProcessMeter

Measuring Electrical Parameters

Measuring Electrical Parameters

The proper sequence for taking measurements is as follows:

1.Plug the test leads into the appropriate jacks.

2.Set the rotary knob.

3.Touch the probes to the test points.

The meter normally automatically selects the lowest range that will measure the applied input signal (Auto showing on the display). Press Kif you want to lock the range. Each time you press K, the meter selects the next higher range.

If you have locked the range, the meter resumes auto ranging when you change to another measurement function or you press Kand hold it for 1 second.

Input Impedance

For the voltage measurement functions, input impedance is 10 MΩ. See the specifications for more information.

Ranges

A measurement range determines the highest value the meter can measure. Most meter measurement functions have more than one range (see the Specifications).

Measuring a Composite Signal

Because the input is dc-coupled, to meaure an ac voltage or frequency with a dc bias, you must manually select the range specified in Table 7. For example, to measure 100 mV ac with 20 V dc superimposed, select the 4 V range.

Table 7. Range Requirements for Measuring a

Composite Signal

Being in the right range is important:

∙If the range is too low, the display shows OL (overload).

∙If the range is too high, the meter will not be displaying its most accurate measurement .

Range (ac)

400.0mV 4.000 V

40.00V

400.0V

1000 V

Max. Allowable AC + DC

3V 30 V

300V

400V

1000 V

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