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Fluke 27 [16/30] Analog bar graph application

Users Manual

High-voltage stacked diode assemblies can usually be

tested for forward and reverse resistance changes using

conductance. These assemblies typically have such high

forward voltage drops that the diode test or resistance

modes cannot test them.

Analog Bar Graph Application

In looking at the analog bar graph, notice that it is

composed of segments that simulate an analog needle.

The bar graph performs the same function as an analog

meter needle, but it eliminates the mechanical overshoot

inherent in needle movements.

A negative (-) annunciator is displayed at the left end of

the bar graph when taking a reverse polarity dc

measurement. Assume that a slowly varying dc voltage is

the input signal. As the input goes more positive (from

zero), a bar graph segment is displayed, and additional

segments are displayed from left to right, to indicate the

input level as it increases. Now, assume that the input

level slowly decreases. Fewer bar graph segments are

displayed as the signal decreases, then the - annunicator

flashes as the signal level passes through 0. As the

signal goes more negative, the - annunciator is displayed

from left to right, indicating a more negative input signal.

The first segment is an indication greater than or equal to

20 counts.

Note that every fifth segment of the bar graph is slightly

larger than those in between, and every tenth segment is

larger yet. These larger segments provide a quick

reference for bar graph indications. The largest segments

(every 10th segment) divide the display into thirds. Thus,

if the bar graph indicates 11 segments on the 32.00V

range, the input voltage is 10 to 11 volts; if the bar graph

indicates 11 segments on the 320.0V range, the input

voltage is 100 to 110 volts. If the input equals or exceeds

3000 counts on the range selected, the bar graph

displays, an arrow at the far right of the display. If the

manual range annunciator (R) is not displayed, the Fluke

27 automatically switches to the next high range if the

input exceeds approximately 3260 counts

Using the Analog Bar Graph

The analog bar graph is most useful in making

adjustments and performing limited diagnostics. Bar

graph response is fast and precise, so it can be used to

easily reach a setting within a few percent of the final

adjustment. The bar graph can be used to make rough

adjustments quickly; then the 3200-count digital display

can be used for final adjustment.

The analog bar graph is useful for performing limited

diagnostics in applications were rapidly fluctuating signal

levels cause the flashing digits of a digital display to be

useless. Like the traditional VOM needle, the analog bar

Fluke 27 [16/30] Analog bar graph application

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