Activity for Carl
| Type | On... | Excerpt | Status | Date |
|---|---|---|---|---|
| Edit | Post #288355 | Initial revision | — | 11 months ago |
| Question | — |
Why do I need electrodes for ECG measurements? When recording an ECG signal, the raw signal is taken from the body and sent into an ECG amplifier to amplify the signal to a suitable range and remove common mode and other types of noise. Measuring the raw ECG signal is done by placing pre-gelled electrodes onto both wrists and one reference ele... (more) |
— | 11 months ago |
| Comment | Post #288010 |
@TonyStewart thank you for the tips. The driven-right-leg technique is used to attenuate common mode residue by an additional factor K, after the differential signal has been sent through the inamp. I don't use a DRL-circuit in this design, because I post-process the data with a moving-average filter... (more) |
— | about 1 year ago |
| Comment | Post #288010 |
@NickAlexeev Please post an answer to this question. You have peaked my interest, but writing this in the comment section is not the proper way I feel.
Please explain what the addition of decoupling capacitors would do to the circuit. (more) |
— | about 1 year ago |
| Comment | Post #288010 |
@NickAlexeev I have not used any decoupling capacitors in this design? Is that a mistake? If so, what would they do to my circuit?
I don't quite understand what you mean with: *What's your analysis for patient isolation*. The patient and amplifier are isolated. The amplifier is powered through two 9... (more) |
— | about 1 year ago |
| Comment | Post #288011 |
Hi Olin, thanks for this tip *This results in one clump of components around an opamp. Now you can move that whole clump around as needed. You can create several independent clumps like that* I struggled with this exact problem during the design. Also thanks for this one *This is the kind of thing th... (more) |
— | about 1 year ago |
| Edit | Post #288010 |
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— | about 1 year ago |
| Edit | Post #288010 |
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— | about 1 year ago |
| Edit | Post #288010 |
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— | about 1 year ago |
| Edit | Post #288010 | Initial revision | — | about 1 year ago |
| Question | — |
What is a good PCB-layout? I am an electrical engineering student and I just finished designing an ECG-amplifier circuit. Here is the schematic: - Image alt text It is fairly simple. Initially, there is a 1st order highpass filter. Then, a differential amplification stage with AD620N in-amp followed by a Sallen-Key 2nd o... (more) |
— | about 1 year ago |
| Edit | Post #287954 | Initial revision | — | about 1 year ago |
| Question | — |
What does it mean for a signal to have impedance? What does it mean for signals to have impedance? To me, impedance is kinda like an "extended resistance" that also includes phase shift $$Z = R + jX $$ It makes sense to me that components like capacitors ($ZC = \frac{1}{j\omega C}$) and inductors ($ZL = j\omega L$) have impedances because they... (more) |
— | about 1 year ago |
| Comment | Post #287952 |
I don't think I understand "an ECG signal is high impedance and this easily picks up line voltage E-fields". How can a signal impedance, and why does high impedance easily pick up radiation? (more) |
— | about 1 year ago |
| Edit | Post #287941 |
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— | about 1 year ago |
| Edit | Post #287941 |
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— | about 1 year ago |
| Edit | Post #287941 | Initial revision | — | about 1 year ago |
| Question | — |
Testing instrumentation amplifier with differential signal I am using the AD620 as instrumentation amplifier to amplify the body's ECG signal. An ECG is a differential signal (measured with two electrodes) and I want a differential gain of Gd=1000 . The datasheet has this formula: $Gd=1+\frac{49.4 \: \text{k}Ω}{RG}$ , so using two resistors of 27 Ω gi... (more) |
— | about 1 year ago |
| Comment | Post #286114 |
Thank you very much for your clear answer. Also, thank you very much for that LT-Spice simulation. I encourage you to keep including these kind of simulations in your answers, because they inspire and teach the rest of us how to use LT-Spice! (more) |
— | about 2 years ago |
| Comment | Post #286112 |
Hi Olin, thanks for your answer. I have edited the question and added some formulas given by my instructor and it looks like I used the wrong one. Using the formula for a buck-boost converter gives me d = 0.45...
However, your answer is making me a little confused. Isn't buck-boost just as well-defi... (more) |
— | about 2 years ago |
| Edit | Post #286110 |
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— | about 2 years ago |
| Edit | Post #286110 | Initial revision | — | about 2 years ago |
| Question | — |
Duty cycle of buck-boost converter I have the following problem: - >Image alt text Using Wikipedia I find that during CCM we have the relation: - $$\frac{V{out}}{V{in}} = -\frac{D}{1-D} $$ Solving for \$D\$ and inserting values gives me $$D=\frac{20\text{V}}{20\text{V}-24\text{V}} = -5 $$ But this doesn't seem to mak... (more) |
— | about 2 years ago |
| Comment | Post #285820 |
@#52987 Yes exactly. Simplicity. I also think you should be able to upvote a comment, so that you can show that you agree with it, without having to post another comment just to say "I agree". And actually, I think it would be a good idea if you could get reputation from those "comment upvotes", if t... (more) |
— | about 2 years ago |
| Comment | Post #286033 |
Thanks for your answer, Olin. This was exactly the kind of answer that I needed - no ambiguity what so ever. (more) |
— | about 2 years ago |
| Comment | Post #286032 |
@#53072 Yeah this is homework. Should I include it in the title? The values are given by my instructor and are not found in a particular datasheet. (more) |
— | about 2 years ago |
| Edit | Post #286032 | Initial revision | — | about 2 years ago |
| Question | — |
Case temperature of MOSFET Homework problem > A MOSFET has a power dissipation of $P{d} = 10\text{W}$. The MOSFET is mounted on a heatsink. There is an isolation pad between the MOSFET case and the heatsink. We are given the thermal resistances: - > > Junction to case: $R{th,jc}= 1.7 \: \frac{°\text{C}}{\text{W}}$ > > I... (more) |
— | about 2 years ago |
| Comment | Post #285820 |
@#53042 This post is not only about traffic but also about "Making a good first impression" which the site currently does not in my opinion. If you think the site looks better than SE you are delusional. Anyway thanks for the downvote. I'm glad I took the time to give constructive inputs only to rece... (more) |
— | about 2 years ago |
| Edit | Post #285820 |
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— | about 2 years ago |
| Edit | Post #285820 |
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| Edit | Post #285820 | Initial revision | — | about 2 years ago |
| Answer | — |
A: How can we grow this community? I think this site needs to get an aesthetic make-over in order to make users coming back. This may be because I'm accustomed to StackExchange's appearance but to be honest, this site is ugly and unappealing visually. The only colour present other than white (which is about 95%) is blue. There ... (more) |
— | about 2 years ago |
| Comment | Post #285792 |
But it does violate the textbook. The Bode Plot on the left is a plot of \$H(j\omega)\$ which should be meaningless according to Lathi. But it is clearly not meaningless. (more) |
— | about 2 years ago |
| Comment | Post #285786 |
Hi Olin thanks for your answer. Yes, I realize you need the system to be stable before you can start designing any form of controller. The problem I have is that there seems to be a disconnect between theory and real life. If I have a system with a pole in the RHP I can use the Nyquist Plot of \$H(j\... (more) |
— | about 2 years ago |
| Edit | Post #285780 |
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— | about 2 years ago |
| Edit | Post #285780 | Initial revision | — | about 2 years ago |
| Question | — |
H(jω) does not exist for unstable systems, but we still use it when designing controllers - contradiction? According to Signal processing and linear systems by Lathi, the transfer function \$H(j\omega)\$ does not exist for systems with poles in the RHP: - Lathi This makes sense to me, since \$H(j\omega) = \frac{Y(j\omega)}{X(j\omega)} \$. However, since the system is unstable \$Y \$ is unbounded (an... (more) |
— | about 2 years ago |
| Comment | Post #284076 |
@#54107 The question and answers you have given are poorly presented and not easy to read/understand. The question is too specific to be useful for anyone other than yourself. And most importantly, the solution in your answer is incorrect! That is unacceptable and, honestly, embarassing. (more) |
— | over 2 years ago |
| Comment | Post #284076 |
@#36396: Understood. But this doesn't seem like a question that matches the description you have given, in my opinion. (more) |
— | over 2 years ago |
| Comment | Post #284076 |
Why are you answering your own questions? If you already know the answers why even post the question in the first place? (more) |
— | over 2 years ago |