Fluke 787 [21/50] Measuring electrical parameters

ProcessMeter

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.

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).

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 .

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 K and hold it for 1 second.

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

Range (ac) Max. Allowable AC + DC

400.0 mV 3 V

4.000 V 30 V

40.00 V 300 V

400.0 V 400 V

1000 V 1000 V