Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Please Help: Impedance Meter

Status
Not open for further replies.

Oluvision

New Member
I am suppose to build Impedance Meter for my Senior Design with the following specifications:

1. Freq 20KHz to 500KHz
2. 1ohms to 1000ohms
3.-180deg-180deg

I have read a lot of confusing literature about this. Does any body have an idea on how to implement both the magnitude and phase measurement circuit on the same circuit.
 

crust

Member
I dont think it is too difficult to do both amplitude and phase in the same measurements. Is it supposed to be all analog (i.e. outputs a voltage/current that represents the phase/impedance) or do you have some type of analog-to-digital conversion and then use a micro to handle the rest of the system?

Since you are setting the frequency yourself, if you are supposed to do the work in the digital domain, you can do a very simplistic DFT that would just need 1 multiplication per sample. You would then have both the amplitude and phase of the output signal. If you also capture the input signal, then the change in phase/amplitude is easily measured.

In the analog domain, you would build a phase detector circuit that would give you a voltage that is linear with respect to the phase difference between the input/output signal. The RMS amplitude difference in conjunction with the known source impedance could then be output.
 

Oluvision

New Member
For: Crust Re: Impedance Meter

Thanks for your assistance Expert Crust

Crust:
"Since you are setting the frequency yourself, if you are supposed to do the work in the digital domain, you can do a very simplistic DFT that would just need 1 multiplication per sample. You would then have both the amplitude and phase of the output signal. If you also capture the input signal, then the change in phase/amplitude is easily measured. "


Can you please explain more about DFT(above paragraph) and the digital procedure in general. Also a circuit diagram (if available) will be apprecitated).
 

Noggin

Member
do a search on DFT (discreet fourier transform) on google. You'll find several good descriptions on how to do it.
 

Russlk

New Member
To measure the phase, use a small resistor in series. It should be small compared to 1 ohm. Comparing the voltage across the current sense resistor with the voltage across the DUT (device under test) in a X-OR gate will give the phase angle. plus or minus 90 degrees is doable, but I don't know about 180 degrees.
 
Status
Not open for further replies.

Latest threads

EE World Online Articles

Loading
Top