Author Topic: THD measurement procedure for Keithley 2015 THD  (Read 1473 times)

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Offline diydidi

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THD measurement procedure for Keithley 2015 THD
« on: May 05, 2016, 06:18:00 pm »
Can anyone give me some step by step instuctions to do THD measurements with this piece of gear.
I would like to be able to do this from the panel buttons only and not via GPIB.
Nowhere on the net does anyone explain this. Gery Sweeney comes close, but he isn't returning my mail  :-//
Any help welcome.
 

Offline jpb

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Re: THD measurement procedure for Keithley 2015 THD
« Reply #1 on: May 05, 2016, 08:29:49 pm »
It is all on page 2-35 of the manual onwards:

Select the function
From the front panel, select the measurement function by pressing SHIFT then THD.

Set the distortion measurement type
1. Press THD-MEAS and the display shows "TYPE: THD".
2. Use the right cursor to highlight the type selection, then use the  and  keys to select
THD, THD+N, or SINAD.
3. Press ENTER, then press EXIT.

Set the distortion frequency acquisition
The Model 2015 must know the fundamental frequency of the input waveform. Even a
difference of a few hertz can cause large errors. The choices are AUTO, SET, and ACQUIRE.
AUTO acquires the frequency before each distortion reading. This slows down the reading rate,
but it is useful if the source frequency is unknown or unstable. ACQUIRE takes a frequency
measurement once and uses it for distortion measurements. SET allows you to select a frequency
between 20 and 20kHz (60Hz is default). AUTO or ACQUIRE are recommended instead of SET,
as the programmed frequency of the external source may not be accurate.
1. Press THD-MEAS.
2. Press ENTER once and the display shows "FREQ: AUTO".
3. Use the cursor keys to select AUTO, SET, or ACQUIRE. (The source must be connected
and turned on for ACQUIRE.)
4. Press ENTER. If SET was selected, you are prompted for the frequency to be used. Use
the cursor keys and press ENTER to select it.
5. Press EXIT.
Set number of highest harmonic
This option sets the number (n) of the highest harmonic included in the distortion calculation,
where "n" is between 2 and 64 (2 is default). For example, the harmonic with a frequency twice
that of the fundamental is the second harmonic (n=2). This function acts as a brick-wall, lowpass
filter. It has an upper limit of 50kHz or 64 times the fundamental frequency, whichever is
lower. This option has no effect in the THD+n or SINAD modes.
1. Press THD-MEAS.
2. Press ENTER until the display shows "UPPR HARM: 02".
3. Set the number of the highest harmonic using the cursor keys.
4. Press ENTER, then press EXIT.

Set measurement units
For the THD and THD+n modes, the measurement units can be percent or dB. SINAD is
always displayed as dB.
1. Press THD-MEAS.
2. Press ENTER until the display shows "UNITS: PERC".
3. Select PERC or dB using the cursor keys.
4. Press ENTER, then EXIT.

Select shaping filter
The Model 2015 has digital shaping filters to simulate having the sample signal pass through
various types of telephone lines. The filter is turned off by default (NONE).
1. Press THD-MEAS.
2. Press ENTER until the display shows "SFIL: NONE".
3. Select NONE, C (C message weighting), CCITT, CCIRARM, A (A weighting), or CCIR
using the cursor keys.
4. Press ENTER.

Set the voltage range
The Model 2015 defaults to autoranging for the voltage input range. If you prefer manual
ranging, use the lowest possible range for the signal level. Not using the appropriate range
causes inaccurate readings, or the display may show "OVRFLW" or "UDRFLW

While the 2015 is measuring distortion, press the manual range keys. The display shows the
new range briefly. Press AUTO for autoranging.

There is more on measuring harmonics etc.
 


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