Digital Multimeter HDM3055 Series Manual

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Math - Null

A null reading is a value that is subtracted from all subsequent measurements. The value is specific

to the present function and will persist even if you leave this function and return to it later.

One common use of this feature is to remove lead resistance from a resistance measurement. To do

this, simply short the test leads together and press [Null]. For other measurement functions, place

the probes across a null value circuit before pressing [Null].

You can also specify a null value by pressing [Math], changing the first softkey to Value, and entering

the value using the arrow keys. To turn off the null feature, press [Null] again or press [Math] and set

the first softkey to Off.

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Math - dB/dBm Scaling

The dB and dBm scaling functions, which apply to ACV and DCV measurements only, allow you

to scale measurements relative to a reference value.

NOTE Scaling is set to OFF when you change measurement functions (for example, changing

from DCV to ACV). You must re-enable scaling after changing measurement functions.

Front Panel Menus

The dB and dBm functions are accessed from the second softkey in the [Math] menu.

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NOTE For accurate displayed statistics of AC measurements in Front Panel mode, the default

manual trigger delay

([Acquire] > Delay Man) must be used.

The first softkey on this menu (shown below) hides or shows the statistics below the data display

(number, bar meter, trend chart, or histogram).

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Remarks

l The Span value is the Max minus the Min.

l Press Clear Readings to clear reading memory and re-start statistics calculation.

Math - Limits

Limit checking indicates how many samples have exceeded specified limits and visually indicates when

the limits are exceeded.

Front Panel Menus

The limits menu is accessed from the [Math] menu.

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The first softkey enables or disables limits. The second and third softkeys specify the limits either

as high and low values or as a span around a center value. For example, a Low limit of -4 V and

a High limit of +7 V are equivalent to a Center of 1.5 V and a Span of 11 V.

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The Beeper softkey enables or disables beeping when limits are violated (this also enables or

disables the beeper for the other functions that use the beeper - probe hold, diode, continuity,

and errors. Clear Condition resets the limit borders to green, as described below.

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Limit Indications

The display uses colors to indicate limits and limit violations.

Trend Chart

The limit area is shown in light red on the graph. The limit borders are green (shown below) as long

as the limits have not been exceeded.

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When a limit is exceeded, the border turns red. In the image below, the top border is still green,

but the bottom border has changed to red because the trend line has gone into the lower limit area.

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The border will remain red even if the trend line moves out of the limit area. When the trend line is

within limits, you can reset the borders to green by pressing Clear Condition.

Note also that the number of the newest displayed measurement, +01.9523 VDC below, indicates

whether the measurement is within limits. Because the limit is 2 V, the 1.9523 VDC value is shown

with the standard background.

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In contrast, the 2.0474 VDC reading is highlighted in red to indicate that it is outside the limits.