Digital Multimeter HDM3055 Series Manual

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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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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 - Introduction

The [Math] key is the shifted [Null]:

These math functions are available:

Null

l dB/dBm Scaling

l Statistics

l Limits

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In Probe Hold mode, the instrument optimizes measurement settings to allow reliable detection of

stable signals (these settings are restored to their original values when you exit Probe Hold.) When

you probe a signal, the instrument beeps (if the beeper is enabled) and automatically records a

measurement when it finds a series of stable readings. You may take additional readings without

pressing [Probe Hold] again.

Press Remove Last to remove the last reading from the list. Press Clear List to remove all

readings from the list.

Because the Probe Hold display is optimized for the Probe Hold readings, you may not combine

it with other display modes, such as histogram, bar graph, trend chart, or statistics.

Probe Hold is a front panel only function. Readings recorded in Probe Hold mode cannot be

accessed from remote. You can, however, take a screen capture of the probe hold display,

see Utility Menu - Manage Files for details.

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Probe Hold

Because probing small areas requires careful concentration, it is often difficult to read the instrument

display while taking measurements. Therefore, the instrument includes a front panel [Probe Hold]

key that allows you to take readings without viewing the display. You can generate up to eight readings

and hold them on the display for later viewing. These readings may be of different measurement types

and you may clear displayed readings at any time.

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These actions do not clear reading memory:

l Changing measurement parameters, such as range and aperture.

l Turning limits on or off, or adjusting limit values

l Pressing [Run/Stop] in front panel auto trigger mode

l Changing the trend chart Recent/All softkey

l Changing samples per trigger or trigger delay

l Changing display modes

l Changing the VM Comp output polarity

l Changing the digit mask

l Changing the histogram, bar meter, or trend chart scale

l Changing user preferences

l Executing self-test

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Clearing Reading Memory

The following actions clear reading memory:

l Changing the measurement function

l Pressing any Clear Readings softkey

l Transitioning in or out of Probe Hold

l Changing temperature units

l Changing any dB/dBm parameters

l Changing any histogram binning parameter

l Changing the temperature probe or R0

l Recalling a stored state

l Calibrating the instrument

l Switching between 3 A and 10 A inputs

l Changing the position of the Front/Rear switch

l Transferring from Remote to Local mode

l Turning Null on or off or changing the Null value

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You can also take one reading or a specified number of readings by pressing [Single].

To save readings, press [Acquire] > Save Readings. Then use the menu that appears to configure

the location where you want to save the readings:

When finished configuring reading storage, press Done > Save Readings to save the readings in

memory to a file.

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Storing and clearing readings

You can store up to 1,000 measurements in the reading memory. Readings are stored in a first-in,

first-out (FIFO) buffer; when reading memory is full, the oldest readings are lost as newer readings

are taken.

In Local (front panel) mode, the instrument collects readings, statistics, trend chart and histogram

information in the background, so if you select any of those options, the data is ready for viewing.

In Remote (SCPI) mode, the instrument does not collect this information by default.

Changing the instrument from Local to Remote does NOT clear any readings in memory. Changing

the instrument from Remote to Local DOEs clear any readings in memory.

In general, you turn the reading of measurements on and off by pressing [Run/Stop], as described

above.

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Trigger delay and multiple samples

The instrument inserts a trigger delay between the occurrence of a trigger and the first measurement.

When Auto is used (Delay Auto softkey), the instrument automatically determines the delay based

on function, range and integration time. However, you may need to manually set a delay (Delay Man

softkey) longer than the automatic delay to allow the input to settle before pacing a burst of measurements,

for measurements with long cables, or for measurements of high capacitance or high impedance signals.

If you have configured the instrument for more than one sample per trigger (Samples /Trigger softkey),

in all cases, the first sample is taken one trigger delay time after the trigger occurs.