What is the difference between heart rate monitor and oscilloscope - Page 1
Forum section: electronics / beginners

author: Decee1
author_rank: Regular Contributor
timestamp: October 31, 2015, 08:24:42 pm
content: Hello Guys. I just signed up here as a fan of EEVBlog because somebody asked me the question "What is the difference between heart rate monitor and oscilloscope" and i didn't know so i would like to ask in here does anyone know? It could be a great video, explaining the difference

author: alsetalokin4017
author_rank: Super Contributor
timestamp: October 31, 2015, 08:31:37 pm
content: A heart rate monitor is an oscilloscope, dedicated to one particular task, with appropriate input sensors, timebase and etc. An oscilloscope is a time-domain voltmeter; that is, it measures voltages as they vary (or not) across time. You could take an oscilloscope (a general purpose instrument) and use it to monitor heart rate with the appropriate sensor. It would be much more difficult to take a heart-rate monitor and use it, say, to troubleshoot your broken electronic alarm system.It has been said that the Lathe is the King of Tools. Just so, and the Oscilloscope is the King of Test Equipment.

author: Maxlor
author_rank: Frequent Contributor
timestamp: October 31, 2015, 09:03:44 pm
content: If you're talking about an electrical monitor like those polar chest straps: they look for aQRS complex, which might have an amplitude in the 2mV range on someone's chest. It needs very strong common mode rejection and pass band filtering with high filter order to be able to isolate that signal. Even then, it gets it wrong sometimes because movement of other muscles in your body will cause interference, e.g. you won't see much of your heart's electrical signal while flexing your chest muscles. It usually employs quite a bit of amplification, up to 1000x depending on how the QRS detection is implemented. Triggering on the signal is fairly trivial, because after filtering, a bump in an otherwise mostly flat signal is all that should remain, and it always has nealy the same width and mostly the same amplitude regardless of the HUT (heart under test)An oscilloscope on the other hand works with a very wide range of signals. To that end, scopes don't usually employ filters (other than a low pass to avoid aliasing, or the basic high pass for AC coupling). They commonly attenuate instead of amplify the signal. And the triggering... actually, I have no clue how non-basic triggering is implemented on a scope. How do you do advanced things like trigger on a certain slope steepness?

author: Karel
author_rank: Super Contributor
timestamp: October 31, 2015, 09:33:13 pm
content: Everything. They are two completely different devices without any similarities.A heartrate monitor shows the heartrate expressed in beats per minute which can be displayed with some simple 7-segment led displays.An oscilloscope visualizes electrical waveforms using a crt or a lcd/tft screen.

author: Richard Crowley
author_rank: Super Contributor
timestamp: October 31, 2015, 09:39:42 pm
content: In a way, I agree with @Karel. The question posted by @Decee1 does not specifically identify what he means by "heart rate monitor" If he means a simple numeric readout of RATE, then @Karel is right that it bears almost no similarity to an oscilloscope. It would be more like a frequency counter one would find on an electronics workbench.But if @Decee1 means something with a graphical representation of the WAVEFORM (Q-R-S complex, etc.), then his "heart rate monitor" is quite similar to a general purpose oscilloscope. But with more specialized input circuit, triggering and sweep controls, and simplified user interface.

author: Karel
author_rank: Super Contributor
timestamp: October 31, 2015, 09:59:17 pm
content: A device that displays the ecg waveform is usually called an ecg/ekg monitor.This device is very similar to an oscilloscope. The most important differences are:1. if not battery operated, the device has a very high electrical insulation from the powersupply and very low leakage currentin order to protect the subject.2. it uses a differential amplification system with very high common mode rejection in order to keep 50/60Hz noise to a minimum.3. bandwith is usually limited to about 0.1 to 500 Hz.4. filters can be selected to improve the signal quality (like 50/60Hz multiple notch including harmonics).5. it can be equipped with pacemaker impulse detection.6. it's usually equipped with very strong input protection to withstand 5KV impulses from defibrillators.

author: McBryce
author_rank: Super Contributor
timestamp: October 31, 2015, 10:05:58 pm
content: Of course he meant an ECG/EKG, otherwise why would he ask what the difference is in the first place??McBryce.

author: nbritton
author_rank: Frequent Contributor
timestamp: October 31, 2015, 10:09:49 pm
content: What do I need to view my heart beat on my oscilloscope?

author: nbritton
author_rank: Frequent Contributor
timestamp: October 31, 2015, 10:12:32 pm
content: Quote from: McBryce on October 31, 2015, 10:05:58 pmThere is no difference between an ECG and EKG, they are the same test, ECG is British English and EKG is American English.

author: Richard Crowley
author_rank: Super Contributor
timestamp: October 31, 2015, 10:32:43 pm
content: Quote from: nbritton on October 31, 2015, 10:09:49 pmYou could view the blood flow profusion through your finger capilaries with something like an oximeter finger clip like this...http://www.ebay.com/itm/2015-A-Adult-Finger-Clip-Spo2-Sensor-Compatible-Nellcor-DS-100A-7-pins-1-METER-/261734388270Those use optical transmission through your finger so there is no potentially dangerous electrical connection.Or, if you wanted electrical signals like ECG, EMG, EEG, etc, then must be MUCH more careful not to kill yourself with direct electrical connection to your body. If you use direct electrical connection you MUST observe very stringent isolation protocols to protect yourself.Wireless solutions are inherently safe. Either those that transmit real-time signals, or those that record them internally.For example here is a gadget I found with a quick Ebay search.http://www.ebay.com/itm/TrueSense-Kit-EEG-ECG-EMG-EKG-tiny-wireless-wearable-bio-sensor-complete-system-/161742298872And I have seen other board-level kits for these kinds of gadgets. Google can probably find them. But BE CAREFUL!!!

author: Maxlor
author_rank: Frequent Contributor
timestamp: October 31, 2015, 11:57:20 pm
content: Quote from: nbritton on October 31, 2015, 10:09:49 pmIt takes a bit of circuitry to do the amplification required to get a signal the oscilloscope can actually pick up. This is a cheap way to do it, if you just want to see the end result:https://www.olimex.com/Products/Duino/Shields/SHIELD-EKG-EMG/open-source-hardware. They also have an ungrounded variant that's basically a 1:1 implementation of a TI app note, also linked on the product page:https://www.olimex.com/Products/Modules/Biofeedback/MOD-EKG/open-source-hardware. I've built a modified version of that circuit myself, it works pretty well. The critical component is the INA321, i.e. an instrumentation opamp with high CMRR, for everything else you can use jelly bean parts, and simplify (e.g. no DAC required, resistive voltage divider works too.)Quote from: Richard Crowley on October 31, 2015, 10:32:43 pmParanoia much? All of us have touched an oscilloscope probe with bare hands, and lived to tell to tale...There is a good reason to do this wirelessly however: you'll pick upa lotless 50Hz noise. But, filtering also works.

author: Karel
author_rank: Super Contributor
timestamp: November 01, 2015, 12:03:13 am
content: Quote from: nbritton on October 31, 2015, 10:09:49 pmHave a look at page 14 of this datasheet:http://www.analog.com/media/en/technical-documentation/data-sheets/AD620.pdfBuild the circuit, operate it from a battery and put an optocoupler between the output and the scope.Do not make any galvanic connections.

author: nbritton
author_rank: Frequent Contributor
timestamp: November 01, 2015, 06:51:52 am
content: Quote from: Maxlor on October 31, 2015, 11:57:20 pmI've never understood this precaution because a scope front end is a passive device. I suppose if your house had a ground fault it could in thoery be potentially dangerous, but the solution to that is to simply float yourself. What's the reason for such paranoia?

author: Karel
author_rank: Super Contributor
timestamp: November 01, 2015, 08:13:32 am
content: Quote from: nbritton on November 01, 2015, 06:51:52 amThe (basic) requirements for this can be found in a technical standard IEC60601. Short story, it's designed by smart people who wanted to see themselves protected against mistakes and/or dumb people (yes, they also work at hospitals).Also, there is a difference between touching with your fingers a device or lying on a bed with ten electrodes containing conducting gel attached to your chest after having a heart attack.In a hospital, when somebody makes a mistake, another person can die because of that.With hobby electronics, when somebody makes a mistake, he/she usually risks to kill himself/herself.The latter is also known as "natural selection". Because of that, IMHO no safety rules need to be applied for non-commercial (medical) electronics as long as it's only used by the person who designed and built it. Nature will take care of it.

author: Simon
author_rank: Unknown
timestamp: November 01, 2015, 08:20:14 am
content: Quote from: Karel on October 31, 2015, 09:33:13 pmDon't be dense

author: Maxlor
author_rank: Frequent Contributor
timestamp: November 01, 2015, 12:15:09 pm
content: Working in the medical devices field, I feel that the regulations and procedures that companies have to follow have long since surpassed the level of reasonable risk management, and it's approaching the situation of nuclear radiation regulation in some fields, i.e. things are being done not because they're necessary, but because they're technically possible. People keep constructing scenarios that are less likely to happen than, say, being struck by an airplane engine that's fallen off its plane, then find technical solutions for that and make everyone implement it. Why is it so? It's imo the result of our risk-adverse and litigous culture. If there's someone in a position to make a decision on whether to burden the industry with yet another safety feature they have to implement, is he going to say "No, that's unnecessary, the situation this is designed to handle is irrelevant", or "Well, I guess itmighthappen someday, and if it does it'll come back to me... better play it safe."I mean, consider what's required for a fatal shock through an oscilloscope, even in the scenario of gel pad electrodes on both sides of your chest. There'd have to be a line power annomaly that makes its way through your switchboard and scope PSU, then damages the scope in such a way that puts high voltage on all the low voltage circuitry, damaging all the components in such a way that they all fail closed, including the 1MOhm input resistor? Then finally, if the power does get to your body, it'd need to keep going for a long time (which also implies the FI switch in your switchboard doesn't work), or you'd need to have a previously undiscovered heart condition that keeps your heart from restarting on its own after it's been interrupted by an electric shock (like healthy hearts do).If something is less likely to kill me than, say, the daily commute to work, I don't see much reason to worry about it.

author: Simon
author_rank: Unknown
timestamp: November 01, 2015, 12:21:01 pm
content: Quote from: Maxlor on November 01, 2015, 12:15:09 pmAnd you would also be surprised on how little testing some companies do on vital equipment..... ahem nuf said.

author: HighVoltage
author_rank: Super Contributor
timestamp: November 01, 2015, 01:20:43 pm
content: Quote from: nbritton on October 31, 2015, 10:09:49 pmI built this before, just for fun to see my heart signal on a scope.The easy setup:You need a differential amplifier with 2 electrodes close to the heart and a third electrode for ground reference, far away from the heart.The more difficult setup:12 electrodes, and much more complicated.There is a different thread somewhere here on the forum, where we discussed this in detail.

author: Karel
author_rank: Super Contributor
timestamp: November 01, 2015, 03:32:30 pm
content: Quote from: HighVoltage on November 01, 2015, 01:20:43 pmIt's not difficult, just take an ads1298. Most difficult part is probably reading all the details of the datasheet.For input protection, a handfull of resistors and gasdischarge tubes will do the job.For isolation, take a digital isolator that satisfies the needs for creapage distance, insulation and speed.Even without a dedicated ecg-chip it's not more difficult. A three lead version does not differ from a ten lead version,it's almost like copy and pasting an inputchannel to create multiple inputchannels.Edit:If the goal is to display all the traces on a 2 or 4-channel scope, that's another story...

author: PA0PBZ
author_rank: Super Contributor
timestamp: November 01, 2015, 06:38:33 pm
content: QuoteI'd say that the probes from the heart rate monitor will hurt a lot less

author: tooki
author_rank: Super Contributor
timestamp: November 01, 2015, 08:13:37 pm
content: Quote from: nbritton on October 31, 2015, 10:12:32 pmAmerican usage borrowed the German abbreviation, didn't it?

author: Simon
author_rank: Unknown
timestamp: November 01, 2015, 08:35:00 pm
content: Quote from: tooki on November 01, 2015, 08:13:37 pmProbably to make sure it was different from the British. They have a huge inferiority complex. American shoe sizes are 1 bigger than ours, exactly the same sizes they just added 1 to everthing so a british 10 is an amercan 11, the conversion "tables" look so stupid, just a list of the same numbers shifted up one.

author: tec5c
author_rank: Frequent Contributor
timestamp: November 02, 2015, 04:02:56 am
content: If I had a dollar for every thread that was made by a newbie who then goes MIA....

author: Simon
author_rank: Unknown
timestamp: November 02, 2015, 06:31:09 am
content: "MIA" ?

author: newbrain
author_rank: Super Contributor
timestamp: November 02, 2015, 06:45:26 am
content: Quote from: Simon on November 02, 2015, 06:31:09 amMissing In Action (or Mostly Ignoring Answers)

author: tec5c
author_rank: Frequent Contributor
timestamp: November 02, 2015, 07:02:44 am
content: Quote from: newbrain on November 02, 2015, 06:45:26 am

author: Circlotron
author_rank: Super Contributor
timestamp: November 02, 2015, 11:18:06 pm
content: DIY ECG.http://www.siliconchip.com.au/Issue/2015/October/An+Arduino-Based+USB+Electrocardiogram?res=nonflash