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5 – Front Panel Operation
3 – Making Front Panel Measurements
As shipped from the factory, front panel measurements are calculated from a total of 2048 readings taken
at a 46.8 microsecond sampling rate. The unit alternates between voltage and current measurements.
Therefore, the data acquisition time for a single front panel voltage or current measurement is about 100
milliseconds. This sampling rate and data acquisition time combined with a built-in windowing function,
reduces errors due to sampling a non-integral number of cycles of a waveform for frequencies of 25 Hz
or greater. Note that the windowing function is less accurate when measuring output waveforms for
frequencies less than 25 Hz, causing the front panel meter to jitter.
The following figure illustrates the various measurements that are returned from a sampled output
waveform. These include measurements such as peak (max), minimum, high level, and low level as
illustrated in the following figure. Rms and dc voltages are calculated from the number of points in the
measurement window.
V or A MAX
V or A HIGH
Figure 5-5. Default Front Panel Measurement Parameters
There are no trigger controls for front panel measurements. However, you can vary both the sampling
rate and the number of data points in each front panel measurement using commands in the Input menu.
With this flexibility, measurement accuracy can be improved for waveforms with frequencies as low as
several Hertz. The sample buffer size may be varied from 1 to 2048 data points in discrete binary values.
The sampling rate may be varied from 15.6 microseconds to 1 second. Values are rounded to the nearest
15.6 microsecond interval. Note that the front panel sample interval and buffer size settings are
independent of the sample interval and buffer size that you program over the HP-IB. This is because you
can qualify measurement triggers over the HP-IB, which makes the HP-IB measurements independent of
the front panel measurements. Refer to chapter 8 for more information about HP-IB measurements.
Two current measurement ranges can be selected in the Input menu. A high current range is available for
measuring output currents of up to 7 amperes. A low current range is available for improved resolution
when measuring output currents below 20 milliamperes. The low current measurement range is accurate
to 0.1% of the reading ±2.5 microamperes. When the current Range is set to AUTO, the unit
automatically selects the range with the best measurement resolution.
NOTE:
If the front panel display indicates OVLD, the output has exceeded the measurement
capability of the instrument. If the front panel display indicates -- -- -- -- -- -- , an HP-IB
measurement is in progress.
42
46.8 microsecond
sampling rate
V or A LOW
V or A MIN
100 millisecond
acquisition time
Measurement samples may not
NOTE:
coincide with the actual maximum
or minimum point of the waveform.
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