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THD Measurement with 2015

2015, 2015-P, 2016, 2016-P
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JSE009
Posts: 2
Joined: September 6th, 2015, 4:33 am
Country: Netherlands

THD Measurement with 2015

Post by JSE009 » September 6th, 2015, 4:56 am

Hello,

I am new on this forum so please forgive me when I aks "known" questions ;)
Last week I received my 2015 which I purchased (second hand) and after playing around with it for a couple of days, I must say
it is a very nice miltimeter to use and to operate.
I have tested almost all function to check if all measurements are within specs and it looks like they are.
But when measuring the THD according to the manuel (2-42) I should read on the display a THD of aprox. <0,2% but instead I read
0,015% and the value is not that stable.
When I do the test bu setting the THD to set and adjust the setting frequency to 1,0001kHz the HTD gets more unstable (just as described
in the manual)

I have tested the output of the function generator on my scope and the signal is 100% perfect and stable.
When hookup my Siglent functiongenerator to the 2015 THD readout is 0,07% for 1 1kHz input signal and this is in my opinion to low according to the specs of the Siglent functiongenerator.

Anyone an idea?

brian.d.smith
Keithley Applications
Keithley Applications
Posts: 402
Joined: June 10th, 2013, 6:00 am
Country: United States

Re: THD Measurement with 2015

Post by brian.d.smith » September 6th, 2015, 10:56 am

When I perform the instructions on page 2-42 of the Users Manual, my model 2015 reads 0.005%. The waveform is pretty much 1.000kHz as measured on an oscilloscope and the RMS magnitude is 1.000VAC.

JSE009
Posts: 2
Joined: September 6th, 2015, 4:33 am
Country: Netherlands

Re: THD Measurement with 2015

Post by JSE009 » September 6th, 2015, 11:38 am

Thanxs for the reply.
So you say that a low reading as I described is not abnormal?
After a long period of warming up, I performed the same test and now the meter reads 0,011% THD and sometimes lower then 0,01% THD.
So the value of 0,2% THD written in the manuel is wrong?

brian.d.smith
Keithley Applications
Keithley Applications
Posts: 402
Joined: June 10th, 2013, 6:00 am
Country: United States

Re: THD Measurement with 2015

Post by brian.d.smith » September 6th, 2015, 1:56 pm

I do not know for sure. I will try to get to the bottom of this and will post the result here.

brian.d.smith
Keithley Applications
Keithley Applications
Posts: 402
Joined: June 10th, 2013, 6:00 am
Country: United States

Re: THD Measurement with 2015

Post by brian.d.smith » September 8th, 2015, 6:19 am

It appears that the manual is incorrect for this exercise.

You can see that the DMM is working if you unplug the input while the measurement is running. The reading goes very high.

If you have a signal generator, you can try a square and a triangle. This should give you some confidence in the 2015.

Positron
Posts: 12
Joined: September 10th, 2015, 5:06 pm
Country: Australia

Re: THD Measurement with 2015

Post by Positron » September 10th, 2015, 7:10 pm

Yes. I also carried out the test of measuring THD according to the manual. I get between 0.005% and 0.010% THD but the measurement is bouncing around like crazy between those figures. Is the jumping normal?
Is there any way to smooth the response time?

Settings
HIZ
1 kHz
1 Vrms
2 Harnonics

Positron
Posts: 12
Joined: September 10th, 2015, 5:06 pm
Country: Australia

Re: THD Measurement with 2015

Post by Positron » September 10th, 2015, 8:07 pm

JSE009 wrote:I have tested the output of the function generator on my scope and the signal is 100% perfect and stable.
When hookup my Siglent functiongenerator to the 2015 THD readout is 0,07% for 1 1kHz input signal and this is in my opinion to low according to the specs of the Siglent functiongenerator.

Anyone an idea?
If you think it is too low for your other function generator, try increasing the number of measured harmonics.
Not sure if that is the right approach but it makes sense to me to try that.

Positron
Posts: 12
Joined: September 10th, 2015, 5:06 pm
Country: Australia

Re: THD Measurement with 2015

Post by Positron » September 22nd, 2015, 5:58 pm

Could you please answer this question.
Is this measurement of 0.005% to 0.01% the limitation of the distortion analyzer, or is this the true measured performance of the signal generator?
I hope the signal generator has better specs than this.

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