Current Ranges And Measurement Detector; Window Functions - Agilent Technologies 66311A User Manual

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7 - Programming the DC Source

When the instrument is turned on and at *RST, the output voltage or current sampling rate is 15.6

microseconds, and the sweep size is set to 2048 data points. This means that it takes about 32

milliseconds to fill up 2048 data points in the data buffer. Adding a command processing overhead of

about 20 milliseconds results in a total measurement time of about 50 milliseconds per measurement.

You can vary this data sampling rate with:

SENSe:SWEep:TINTerval <sample_period>

SENSe:SWEep:POINts <points>

For example, to set the time interval to 46.8 microseconds per measurement with 1500 samples, use

SENSe:SWEep:TINTerval 46.8E-6;POINts 1500.

Note that reducing the number of sample points increases the speed of the measurement; however, the

tradeoff is greater measureent uncertainty in the presence of noise..

Current Ranges and Measurement Detector

The dc source has two current measurement ranges. The command that controls the ranges is:

SENSe:CURRent:RANGe MIN | MAX

When the range is set to MIN, the maximum current that can be measured is 20 milliamperes. The

crossover value of the high and low ranges is 20 milliamperes.

The dc source also has two measurement detectors. Check that the current detector is set to ACDC when

measuring current pulses or other waveforms with a frequency content greater than a few kilohertz.

SENSe:CURRent:DETect ACDC

Select DC as the measurement detector if you are making only DC current measurements and you require

a measurement offset better than 2mA on the High current measurement range. Note that this selection

gives inaccurate results on current waveforms that have ac content.

SENSe:CURRent:DETect DC

The dc source lets you select from two measurement window functions: Hanning and Rectangular. To

select a window function, use:

SENSe:WINDow: HANN | RECT

As shipped from the factory, the dc source measurement functions use a Hanning window. The Hanning

window applies a cos

weighting function to the data in the measurement buffer when computing

measurements such as average and rms. This returns accurate data even if an integral number of

waveform cycles are not captured, provided that at least three or more waveform cycles are in the

measurement buffer. If there are only one or two waveform cycles, the Hanning window will not give

accurate results.

With a Rectangular window, no weighting function is applied to the data in the measurement buffer.

However, to use the Rectangular window function to return accurate data for one or more waveform

cycles, an integral number of of waveform cycles must be captured in the measurement buffer. This

means that you must accurately know the waveform period beforehand. In this way you can chose the

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