Best usage of a decade box I've seen so far...Thanks for the video!

@eie_for_you

3 ай бұрын

🙂 You are very welcome! 😀

I dig your channel and your content. Cheers!

@eie_for_you

3 ай бұрын

Thanks! 🙂

@11:20 Additionally for case #3 you can calculate the theoretical open circuit voltage using either side of the equation shown at this location of the video. Thank you Mr. Gable!🎉

@eie_for_you

3 ай бұрын

True that! You are very welcome! :-)

That was very enlightening, I can use this knowledge, thanks

@eie_for_you

3 ай бұрын

You are very welcome! I'm glad it was helpful. 🙂

Great video Ralph Thank You 😊😊😊

@eie_for_you

3 ай бұрын

Thanks, man! And you are very welcome! 🙂

Very lucid presentation, learned something. Many thanks.

@eie_for_you

3 ай бұрын

Thanks! And you are very welcome! 🙂

Excellent as always! Thanks and have a great one.

@eie_for_you

3 ай бұрын

Thanks, man! Enjoy your day! 🙂

I'm definitely saving this for reference. This is an excellent expansion on W2AEW's also-excellent video on this topic.

@eie_for_you

3 ай бұрын

Thanks, man!🙂

I like the way you explain everything. Subscribed.

@eie_for_you

3 ай бұрын

Thank you! 🙂

Thank you for the Great Video.

@eie_for_you

3 ай бұрын

You are very welcome! :-)

Thank you so much for this, it makes everything so clear; 73 Bob

@eie_for_you

3 ай бұрын

You are very welcome! 🙂

👍Thank you sir.

@eie_for_you

3 ай бұрын

You are welcome! :-)

Loved it

@eie_for_you

3 ай бұрын

I glad you liked it! 🙂

Thank you. One assumption you disclosed was using a "low frequency". At what frequency does a method start to give misleading results? Why are the methods frequency dependant?

@eie_for_you

3 ай бұрын

Well, this depends on the particular method of termination. Using my old Heathkit decade box with all of its leaded resistors inside, this frequency is pretty low...below 100KHz. If you have a "higher end" decade box with all surface mount components, you might get away with higher frequencies. If you are using the third method and have two coaxial termination resistors to make the measurement with, you might be able to use even higher frequencies. The limitation is due to stray inductances and capacitances leading to possible self-resonances and other RF weirdnesses. The rule of thumb with most every measurement is to use the lowest applicable frequency to avoid all of the effects of these strays. Hope this helps. 🙂

So we have a perfect signal source (OP AMP) generating the 1 volt signal. We connect a capacitor between the OP AMP output and the output terminal.. We connect a 50 ohms resistor to the output. We adjust the capacitor to give 1 volt. We hide this in the signal generator cabinet and hand it to you. Will your method and arithmetic still give the proper value? I suspect these simple impedance measuring techniques will only work in a purely resistive circuit.

@eie_for_you

3 ай бұрын

Nice question! You have defined a frequency dependent output impedance. This method will predict the output impedance at a given frequency. By taking similar measurements at one or two frequencies additionally and using some math, you could predict the value of the capacitor and the output impedance at any given frequency. 🙂

Excellent presentation. Using #3 equation for a common collector you will find that Zo is less than 2 ohms.

@eie_for_you

3 ай бұрын

Thank you! Actually.. when it comes to a common-collector configuration the actual Zo is dependent on the quiescent emitter current and it is approximately equal to V(T)/I(EQ) where V(T) is the thermal voltage (0.026 Volts at room temperature) and I(EQ) is the quiescent emitter current. I did use method #3 to determine the output impedance of a common-emitter circuit and it came out to be 12 Ohms. :-)

@rtybn2012

3 ай бұрын

You are right about the Zo is very dependent on Ie. I remembered that after I set that message.

@eie_for_you

3 ай бұрын

@@rtybn2012I've done that! The best editor is the "send" button! 😀

Outstanding presentation Ralph, as usual. KC9PFH

@eie_for_you

3 ай бұрын

Thank you so much Mr. Mike! 😀

Great video. However i miss some information as impedance is not exactly the same as resistance. Also how frequency dependance is this. This as signal sources can also have some capacity or inductance.

@eie_for_you

3 ай бұрын

True ... resistance and impedance are related, but not the same. The frequency dependence is highly dependent on the load you are using. My old Heathkit decade box has a LOT of leaded resistors in it and so I wouldn't want to go above 100KHz with it. However, if you are using a really good decade box with all surface mount parts, you could go higher, depending on the the box. If you are using coaxial terminations, then higher yet. Nonetheless, the general rule of thumb for all such measurements ... the lower the frequency the better to avoid self-resonances and other RF weirdness. :-)

G,day from Sydney Australia. You measured the open circuit V applied resistance to it using an appliance (decade box) and turned the top until half V drop witch was 5 on the knob (5 Ohms). Q1. Is the "decade box" within its specifications? I'd look at the label on the decade box or seek owners manual technical specifications list? ➖💫❌

@eie_for_you

3 ай бұрын

One does have to be very careful not to apply too much current to one's decade box to avoid frying it. As my one bud used to say, "It'd be cactus!" Regarding the setting of the decade box, that was the x10 Ohm dial which was set at the 5, making it 50 Ohms. My decade box is a very ancient Heathkit Model IN-11. I did not build this. I "inherited" it from some forgotten source. I have checked it to some extent (DVM to the terminals), but not extensively (every position of every switch). :-)

Thank you Sir. How does Earth Loop Impedance ( live and Ground) - High and low loop work? I am wondering if you can make a video about it. My mean interest is the circuit diagram not the actual test itself. I need to know for example how Megger tester works or Mega-ohm meter works. Thank you again very appreciated.

@eie_for_you

5 күн бұрын

A megger is a special, high resistance ohmmeter. The resistances are so large that the usual low voltage testing cannot be used because the resulting current is too small. The original models (eons ago - before my time) had a simple analog meter and a crank operated high voltage supply. Newer ones can be very, very sophisticated in setting controls and resistance ranges. These will have limits as they ramp up the voltage ... if they high the limit, they could shut down the supply and terminate the test. In the end, they simply provide a voltage that it applied across the high resistance and then measure the current flowing. A little math knowing both voltage and current and we know what the resistance is. We used to have to use this very kind of device to test conductivity of all of the "furniture" and the floors in the operating rooms at the hospital I worked at so that static couldn't be generated to cause a spark and ignite possible flammable gasses being used. This is much like the "conductive" mats used on electronics benches and the "conductive" bags used for static sensitive devices like transistors and ICs. 🙂

@rtecha.m9648

5 күн бұрын

@@eie_for_you Thank you 😊

@eie_for_you

4 күн бұрын

@@rtecha.m9648 You are very welcome, my friend! 🙂

sir, is there any method to find short circuit in pcb using this analysis ?

@eie_for_you

2 күн бұрын

If you are talking about locating the short on a known trace, I'm afraid that this won't do that for you. Finding shorts on traces is a tough job on a two layer board and **WAY** tough on a multilayer board. With the latter PCB companies often use special X-Ray machines. There are other devices that shoot signals down a trace and you use a special sensor-type instrument to find where the signal stops (short spot).🙂

Excellent video! Can you follow up with input impedance?

@eie_for_you

3 ай бұрын

Thank you! I was actually thinking about that. I can add this to my list of videos to come. :-)

@peterayearst23

3 ай бұрын

I'd be most interested in a video on this subject. At the moment, I've been trying to understand input impedance of a dual gate mosfet. Looking at LTspice simulations, I was surprised at how much the impedance changed over a range of frequencies. In particular, between 1 - 30Mhz. Question now is ho to accurately measure the circuit confirming the simulation results? Thank you for your most informative videos.

@eie_for_you

3 ай бұрын

@@peterayearst23This topic is now on my list of videos to create. The short answer is ... series resistance (Rs) between the signal source and the circuit. Measure the voltage on each side of this series resistance (V1 = source side, V2 = load side). Then use this formula: Rin = (V2*Rs)/(V1-V2). 🙂

@jameswarren1831

3 ай бұрын

While the calculations are straightforward my brain doesn’t work well without a physical demonstration, it’s been broken from the start :)

@eie_for_you

3 ай бұрын

@@jameswarren1831 Aaaah! I see! Well, like I said, it is in the list of requested topics. It will be out ... sometime. Cannot say when, but I will do it! 🙂

Given the proliferation of affordable hobby grade VNAs, it would be interesting to host a demonstration covering the considerations necessary to properly and safely measure the output impedance of a black box device (e.g. maybe it is an amplifier with or without DC offset). Two port measurements of a filter or non-active components are fairly straightforward and well documented. There are already many videos covering input impedance of an arbitrary device using a VNA. Thoughts? Maybe the topic has been covered well elsewhere.

@eie_for_you

3 ай бұрын

Interesting question ... Yes, two port measurements are perfect for filters and even amplifiers provided that one takes proper precautions to protect port 2, the input with proper attenuation between the amplifier output and the VNA input. Using a VNA to perform a one port measurement of the output impedance of an amplifier is quite a different matter. Output impedance is a matter of an *active* device. For instance, the output impedance of a common collector circuit is tied to the transistor itself and the quiescent emitter current. You cannot measure the output impedance of this circuit without the circuit being in an active, powered up, state. I would be very wary of connecting a VNA directly to the output of an amplifier to measure its output impedance because a VNA generally uses and measures very small signal levels. Amplifiers generally provide anything *but* small signals. Connecting a VNA to the output of an amplifier would almost certainly result in the frying of the VNA input at worst and, at best, probably give results that are not altogether commensurate with reality. Afterall, even with no input to the amplifier, it still will have some sort of residual output which will compete with the VNAs anticipated response to its own signal. My take. 🙂

@AzCrawler00

3 ай бұрын

@@eie_for_you That makes sense and confirms what I was envisioning. Even if the output port of the DUT was decoupled to eliminate any DC offset, and the appropriate attenuation added to satisfy the input restrictions on Port 1 (as opposed to Port 0), would that even measure the true output impedance of the circuit? Seems the reactive component (DC block / capacitor) and the attenuator (resistor network) would have an impact on the impedance measured by the VNA. Seems whatever that measurement is would be of the whole circuit and not the actual output port of the device under test, leaving the original question. Maybe there's a way to calculate away the effects of the DC block and attenuator on the captured S parameters to derive the actual impedance of the DUT output. Wonder if a SIMSmith model can help there. I like the two point general method since the other two are really just special cases of that general solution. The other two (very useful) methods are readily derived if needed.

@bretfuzz925

3 ай бұрын

If you perform OSL calibration on VNA with the DC block attached to the VNA, you have nullified the reactance from your measurement. Also, you must terminate the input of the dut. Then you can perform an s11 measurement to the output of the dut using port 1 of the VNA (technically this is an s22 measurement of the dut). Port extension may need to be performed to null out any added cable length. Most people will get confused by the results using smith chart due to rotation from added conductor lengths but it is an accurate method when done properly.

@bretfuzz925

3 ай бұрын

For performing s21 to understand frequency response/gain, ensure your input signal (VNA RF signal level) is sufficiently low that you will not violate the maximum input level to port 2 of the VNA. Rumor has it you can perform through calibration with an attenuator, then ensure that attenuator is used between the output of the dut and port 2 of the VNA. If VNA RF output is too high and you suspect compression, place attenuator at RF output of VNA (port 1).

@eie_for_you

3 ай бұрын

@@bretfuzz925 If we are doing an S21 measurement of an amplifier, then it is very easy to have a high enough output of the amplifier to fry the port 2 input of the VNA. Depending on the expected input level of the amplifier in question will determine if the attenuator should be between port one and the DUT or between port two and the DUT. Yes, performing SOLT calibration with everything BUT the DUT in place is a must. Than way, the only thing we are measuring is the DUT. If the attenuator is to be placed between port one and the DUT, then the SOL portion should be done with the attenuator in place and the standards attached to the end of the attenuator that will connect to the DUT. This might not be possible if the required attenuation is exceptionally high. The object in all cases is to be sure that, when we make our measurement of the DUT, [a] we ONLY are measuring the characteristics of the DUT and [b] we are not damaging our VNA n the process. This all takes careful planning *before* any attempt is made to perform the measurement. 🙂

How about a video using PIN diodes?

@eie_for_you

3 ай бұрын

Hmmm ... I'll have to give that some thought. :-)