## impedance calculation - Power Factor

Forum for discussing PicoScope version 6 (non-automotive version)
NathanUnger
User
Posts: 5
Joined: Wed Sep 27, 2006 9:51 am

### impedance calculation - Power Factor

Hello,
I'm working with a 12 volt AC signal. I have the Voltage on channel A and the TA018 current clamp on channel B
I would like to calculate the impedance using a math channel A/B, and a measurement, but where the current goes through zero, the signal goes out of range. How do I get around this problem?

AndrewA
PICO STAFF
Posts: 252
Joined: Tue Oct 21, 2014 3:07 pm

### Re: impedance calculation

Hi,
I agree, so you want the AC rms value of the impedance? Do also want the reactance and true resistance of circuit as well as phase angle?
See diagram-
http://www.nap.edu/openbook/0309057973/ ... 170001.jpg
Regards Andrew
Technical Specialist

NathanUnger
User
Posts: 5
Joined: Wed Sep 27, 2006 9:51 am

### Re: impedance calculation

Hello,

Of course, the more information I can get, the better, but I don't actually need more than just the AC rms impedance value because I am only making comparison measurements to a "known good" value. I thought there might be some mathematical technique or connection methodology to get around the problem right within Picoscope.

AndrewA
PICO STAFF
Posts: 252
Joined: Tue Oct 21, 2014 3:07 pm

### Re: impedance calculation - Power Factor

Hello,

Most of the calculations cannot be done in PicoScope. But the measurements needed can be exported out. And could be easily be done in excel.
See this post on exporting measurement values-
topic15481.html?hilit=batch
First you need to setup your channels and the measurements needed-
See the screen shot and example psdata file with-

-Channel A for- Volts
-Channel B for- Amps
-Maths channel - ChA x ChB (Instantaneous Power)

The measurements that are exported are-
Volts- rms
Current(Amps) - rms
Apparent Power which is the DC average of Instantaneous Power (Volts x Amps)

The attachment AC vectors and Power factors.psdata is no longer available
Now follow the calculations in the attached pdf.
AC Vectors and Power Factor.pdf
AC vectors and Power Factor cals
Here is Excel file with the calculations included-
Factor factor.xls
Excel calculations
I have not used complex numbers but you could do for some of the calculations.
Attachments
AC vectors and Power factors.psdata
AC vectors and Power Factor
Regards Andrew
Technical Specialist

AndrewA
PICO STAFF
Posts: 252
Joined: Tue Oct 21, 2014 3:07 pm

### Re: impedance calculation - Power Factor

We now have a formula to give a RMS value using a maths channel.

Code: Select all

sqrt(integral(A^2)/T)
Adding '+freq(A)-freq(A)' to it stops the start of the maths channel starting at a lower value.
When using the measures on these maths channels you need to set 'between time rulers' and move time rulers to exclude the start and the end of the maths channel.
I have attached a updated psdata file with these maths channels included.

Channel A must be used for Voltage
Channel B must be used for Current
Remember you can still take the three measurement values-
-'AC RMS' of Channel A for- Volts
-'AC RMS' of Channel B for- Amps
-'DC Average' of Maths channel - ChA x ChB (Instantaneous Power)

As before and enter these into the spreadsheet to check the calculations are correct.

Math channel formulas-
RMS value (channel A)=

Code: Select all

sqrt(integral(A^2)/T)+freq(A)-freq(A)
Power factor =

Code: Select all

((integral((abs(A*B)))/T)+freq(A)-freq(A))/((sqrt(integral((A)^2)/T)+freq(A)-freq(A))*(sqrt(integral((B)^2)/T)+freq(B)-freq(B)))
PF in degrees =

Code: Select all

180/pi(acos(((integral((abs(A*B)))/T)+freq(A)-freq(A))/((sqrt(integral((A)^2)/T)+freq(A)-freq(A))*(sqrt(integral((B)^2)/T)+freq(B)-freq(B)))))
I suggest turning off maths channels you don't need, or adding more 'view' windows if you need more maths channels (VA, Reactance X, etc).
If you are going to be doing three phase with 4824 remember a 'view' window only supports 8 channels/maths channels.
AC vectors and Power factors3.psdata
Regards Andrew
Technical Specialist

vahid1661
Newbie
Posts: 0
Joined: Sun Mar 31, 2019 3:07 pm

### Re: impedance calculation - Power Factor

Hi Andrew,

I am doing a frequency sweep for capacitance and inductance separately.

I want to use FRA and measure Impedance and power versus frequency.

What is the standard way of doing this?

Thanks,
Vahid

AndrewA
PICO STAFF
Posts: 252
Joined: Tue Oct 21, 2014 3:07 pm

### Re: impedance calculation - Power Factor

These maths channels won't in FFT mode in PicoScope 6.
So I would try using the FRA4Picoscope with this new tool-
https://www.eevblog.com/forum/testgear/ ... msg2190516
Regards Andrew
Technical Specialist