Fluke 27 [20/30] Specific applications noisy resistance measurements

Users Manual

Specific Applications--Noisy Resistance

Measurements

Most digital multimeters are so sensitive they can not

tolerate as much as 50 mV of the line noise while making

resistance measurement; their digital displays become

unreadable due to the line noise. On the other hand,

because of the mechanical inertia of the analog needle,

the noise alternately pulls the needle to the left and then

to the right, averaging out any movement and leaving a

fairly stable resistance reading.

The Fluke 27 resistance measurement circuit is designed

to tolerate ac noise far better than the usual DMM.

Readable 2-kilohm readings can be obtained even in the

presence of 1 V ac noise. Readings of 1 megohm may be

obtained with up to 2 V ac noise. The noise appears as

about 50 counts of change and an oscillating bar graph.

Operator Maintenance

WWarnings

To avoid possible electric shock or personal

injury:

• Do not allow water to get inside the case.

• Remove any input signals prior to

removing test leads and opening case.

• When servicing the meter, use only

specified replacement parts.

• Before closing battery door, make sure

fuse cover is in place.

• Make sure the battery door is closed and

latched before you operate the meter.

To prevent arc blast and resulting injury,

install only the EXACT replacement fuse

listed in the Maintenance section.