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Impedance instrument AD2


Jon Frey

Question

Notes and questions on impedance function


Observations
1) Impedance function/capability  not listed on the AD2 Data sheet
2) AD2 data sheet shows only one channel voltmeter

    "Single channel voltmeter (AC, DC, ±25V)
     Network analyzer – Bode, Nyquist, Nichols transfer diagrams of a circuit. Range: 1Hz to 10MHz"


Questions
3) Online manual for the impedance function does not cover use with the BNC adapter
       "Selectable AC and DC coupling to oscilloscope probes
        Selectable 50-ohm or 0-ohm output impedance on arbitrary waveform generator (AWG) channels"


3a) Only DC coupling is shown in the Impedance application selection boxes , so the adapter jumpers  should be set that way ?

3b)  Should output impedance jumper be set to 50 ohm to match BNC cables,  0 ohms  or does the compensation function make it irrelevant ?


4) There is a drop down menu in the application in Wavforms that I did not see explained in the online  Impedance application manual  "Element " with choices Auto, Inductance , Capacitance  and "Model " with choices Series, Parallel. What are these functions ?

 

Settings.PNG.6e8fb675e9acefdb80007fdb18d8c6c6.PNG

 

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Hi @Jon Frey,

1) The impedance analyzer is more of a feature of the WaveForms software rather than the AD2, so it appears that the AD2 reference manual wasn't updated to mention this new feature. I'll see about getting the reference manual updated to reflect this.

2) This is a mistake in the features list; the correct specifications for the voltmeters is listed in section 9.8 of the reference manual. I'll look into getting this updated as well.

3) Agreed; the scope of the impedance analyzer tutorial did not extend to using the BNC adapter.
3a) I believe so yes, but I will defer to @attila on this.
3b) I think you will need usually need to set the output impedance to 0 Ohms, especially when you are analyzing high speed frequencies where exact resistor values used in the calculations done by WaveForms start to make a notable difference.

4) Those change the values displayed in the upper right hand corner (by default the ones showing Ls, RS, @, |Z|, etc) to match what you select. So if you choose to measure the parallel values, the boxes will show the calculated values at the -3 dB point with regards to parallel calculations (if applicable), although it does not auto-update the box labels; you'll need to update another field first (such as the Load First vs Resistor First dropdown menu). I imagine you would also need to set up your circuit in parallel in order for those calculations to have relevant meaning to your system.
I'm not certain on the Auto, Capacitance, and Inductance field since I'm not noting any changes. I'll have to defer to @attila on this functionality.

Thanks,
JColvin

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Thanks for the swift reply and referral to Attila

 

Adding one more  observation and a question

5) Compensation carry over from analyzer to meter seems to have a glitch

I did a open and short compensation in an analyzer sweep.

When I switch to meter mode at  the fixed frequencies , including the end points of the sweep , I get warning  message stating no short compensation.

No setting changed , only running single shot record

It only complains about the short comp and is happy with the open comp recorded in the other screen.

 

5a) Are they separate tables for meter and analyzer?

5b) Will the sweep always get these fixed points or will it miss them due to range selected  divided by samples selected  in the sweep.

5a6808b419b96_Impedancemeterscreen.PNG.7e2ff07882d9fff3e3889b1aa6e9418a.PNG

 

6) Nit picky observation, but spelling error in the warning  message

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Hi @Jon Frey

1. Yes, it is more of a software feature and beside AD2 it can also be used with AD1 and EExplorer.

3. The impedance analyzer usage is flexible. It can be used with wires, breadboard, custom adapter board or bnc adapter. It lets you specify custom probe impedance to match your wiring/circuit.

a. The AC/DC option in the software is intended to switch the input coupling of the device, but so far there is no device with such dynamic option.
The AC/DC scope input selection should only influence the analysis at low frequencies, like below 100Hz.

b. The AWG output impedance does not influence the analysis since only the relation between scope measurements is taken in account. However when analysing low impedance loads (and low reference resistor, <100Ohms) due to output impedance the signal amplitude is more likely to drop reducing the measurement resolution.

4. In analyzer mode the values in top right show the load value at the frequency point which is closer to 45* input phase.
The options in the dropdown take effect for running instrument or for the next run.

5. The compensations are not carried. Separate set is stored for meter and analyzer mode, since in these modes different frequency steps are used.
The compensation for meter mode calculate compensation values for "nice" frequency steps like 10Hz, 20Hz, 50Hz, 100Hz, ... 10MHz

6. Thank you for the observation.

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