Digital Multimeter HDM3055 Series Manual

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If multiple [Single] or external triggers are issued during a series of measurements, all triggers

received after the first are discarded.

The [Acquire] menu also configures the delay that occurs before each measurement is taken,

regardless of the trigger mode (Auto, Single, or Ext). This may be either automatic (the delay is

based on the DMM’s settling time) or manual (you specify the delay time).

Finally, note the [Run/Stop] and [Single] keys on the front panel. In Auto trigger mode, pressing

[Run/Stop] stops and resumes measurements, and pressing [Single] switches the instrument to

single trigger mode. In the Single and Ext modes, pressing [Run/Stop] stops readings if they are

in progress, or switches the mode to Auto if readings are stopped.

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Auto - the instrument continuously takes measurements, automatically issuing a new trigger as

soon as a measurement is completed.

Single - the instrument issues one trigger each time the front panel [Single] key is pressed.

Ext - the instrument issues one trigger each time an edge of the appropriate slope arrives at the

rear-panel Ext Trig connector. You can specify the slope on the softkey menu that appears when

Trg Src is set to Ext.

In the Single, and Ext modes, you can specify the number of samples to be taken per trigger by

using the Samples/Trigger softkey. The Single and Ext modes can both buffer up to one trigger,

meaning that if you press [Single] or receive an external trigger while a series of measurements

is in progress, the instrument will finish that series of measurements and then immediately launch

a new series of measurements based on the trigger.

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The menus above allow you to configure measurement triggering, and you can also use the VMC

Out softkey to set the edge slope of the VM Comp (voltmeter complete) output on the instrument's

rear panel. This connector issues a signal whenever the voltmeter finishes taking a measurement to

allow you to signal other devices in a measurement system.

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

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

The (Trg Src) menu allows you to select one of these trigger sources:

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Instrument trigger model

Acquiring measurements on the DMM is done as the result of triggering. This section describes

how to configure triggering.

Pressing [Acquire] opens the following menu:

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Where:

l Sensor - The raw sensor value; ohms for thermistor/RTD.

l Input/Ref - The DC signal voltage and the DC reference voltage measurements.

1 After making one or more primary measurements for approximately 4 seconds, the DMM makes

one secondary measurement.

Triggering and Readings

The trigger model and large reading memory provide versatile capabilities for a wide variety of applications.

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To select a secondary measurement from the front panel, first select the primary measurement

function and then press Display:

Press 2nd Meas and select the secondary measurement.

The primary measurement functions and their associated secondary measurements for each DMM

model are:

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Secondary Measurements

Most measurement functions allow you to select and display a secondary measurement function.

Secondary measurements can be displayed in the Number and Bar Meter displays only. For example,

a thermistor temperature measurement (primary) and the resistance measurement made on the

thermistor (secondary) are shown below:

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Step 5: Press Gate Time and choose the measurement aperture (integration time) of  10 ms,

100 ms (default), or 1 s.

Step 6: Press Timeout to control how long the instrument waits before timing out on a frequency

or period measurement when no signal is present. When set to 1s, the instrument waits 1 second

before timing out. When set to Auto, the wait time varies with AC filter bandwidth; for the faster

bandwidths, the instrument waits a shorter time before timing out and returning 0.0. This is

advantageous in manufacturing test systems where a DUT failure may result in no signal;

in this case, the failure can be detected sooner, speeding up test throughput.

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

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

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Step 4: Press AC Filter and choose the filter for the measurement. The instrument uses three

different AC filters that enable you either to optimize low frequency accuracy or to achieve faster

AC settling times following a change in input signal amplitude.

The three filters are 3 Hz, 20 Hz, and 200 Hz, and you should generally select the highest

frequency filter whose frequency is less than that of the signal you are measuring, because

higher frequency filters result in faster measurements. For example, when measuring a signal

between 20 and 200 Hz, use the 20 Hz filter.

If measurement speed is not an issue, choosing a lower frequency filter may result in quieter

measurements, depending on the signal that you are measuring.

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Step 2: Press [Freq] on the front panel and then use the first softkey to choose either frequency

or period measurement.

Step 3: Press Range to select a range for the measurement. (Auto (autorange) automatically

selects the range for the measurement based on the input. Autoranging is convenient, but it results

in slower measurements than using a manual range. Autoranging goes up a range at 120% of the

present range, and down a range below 10% of the present range.