Actron AutoTroubleShooter CP7677 User Manual download pdf (Page 6)

6

Setting the Range

Two of the most commonly asked ques-

tions about digital multimeters are What

does Range mean? and How do I know

what Range the multimeter should be

set to?

What Does Range mean?

Range refers to the largest value the

multimeter can measure with the rotary

switch in that position. If the multimeter

is set to the 20V DC range, then the

highest voltage the multimeter can mea-

sure is 20V in that range.

EXAMPLE: Measuring Vehicle Battery

Voltage (See Fig. 1)

Now assume we set the multimeter to

the 2V range. (See Fig. 2)

The multimeter display now shows a “1”

and nothing else. This means the multi-

meter is being overranged or in other

words the value being measured is larger

than the current range. The range should

be increased until a value is shown on

the display. If you are in the highest

range and the multimeter is still showing

that it is overranging, then the value

being measured is too large for the mul-

timeter to measure.

How do I know what Range the multi-

meter should be set to?

The multimeter should be set in the

lowest possible range without

overranging.

EXAMPLE: Measuring an unknown re-

sistance

Let’s assume the multimeter is con-

nected to an engine coolant sensor with

unknown resistance. (See Fig. 3)

Fig. 2

Fig. 1

Let’s assume the multimeter is con-

nected to the battery and set to the 20V

range.

The display reads 12.56. This means

there is 12.56V across the battery termi-

nals.

Fig. 3

Start by setting the multimeter to the

largest OHM range. The display reads

0.0Ω or a short circuit.

This sensor can’t be shorted so reduce

the range setting until you get a value of

resistance.

At the 200KΩ range the multimeter mea-

sured a value of 4.0. This means there is

4KΩ of resistance across the engine

coolant sensor terminals. (See Fig. 4)

If we change the multimeter to the 20KΩ

range (See Fig. 5) the display shows a

Red

Black

Red

Black

Black

Red

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