EEVblog #1008 - Mystery Teardown

[EEVblog]

Mystery Teardown!
What's got two pads and generates a Devo Energy Helmet waveform?

[bjcuizon]

What are the things/studs on top of the binding posts??? Can you plug regular banana plugs?

[EEVblog]

What are the things/studs on top of the binding posts??? Can you plug regular banana plugs?

Some sort of nib for alligator clips maybe?

[bjcuizon]

Oh, Okay. That's a bit rare to see nowadays.

[trophosphere]

What are the things/studs on top of the binding posts??? Can you plug regular banana plugs?

They are standard snap connectors that can be attached to ECG leads of the defibrillator under test for cardiac scenario recognition. See attached picture.

An interesting thing to note is that ECGs must have resistors of sufficient impedance on their inputs for a couple reasons even though it may reduce CMRR and increase offset voltage.

• Prevent excessive energy being lost into the ECG as the ECG will have its own clamping devices (MOVs, GDT, etc) to protect its instrumentation amplifier. This is because without such resistors the clamping devices can shunt energy from the defibrillator through itself and thus reduce the energy through the heart thereby decreasing the effectiveness of the defibrillation. IEC 60601-2-49
• Prevent excessive current from damaging the electrodes because of degradation via heating through thermal losses and augmented oxidation. IEC 60601-2-25 and IEC 60601-2-27
• Limit current through the patient should the instrumentation amplifier fail in such a way that its rails short through the patient via the electrodes

A minimum of about 10k is needed to barely pass the tests for the above such as the Energy Reduction Test but values of around 50k is usually seen. Values around 100k are more commonly seen in monitor mode specific ECGs versus lower resistance values for diagnostic mode specific ECGs.

[TheWelly888]

I use those analysers at work.

The Impulse 3000 is obsolete because they were designed in the days of monophasic defibs and have not been optimised for biphasic defibs (which were introduced circa 2000) It was superseded by the Impulse 4000 analyser which can measure biphasic as well as monophasic defib energies but even that has been superseded by the Impulse 7000 which has a greater choice of simulated ECG waveforms.

Different models of defibs can analyse the ECG waveform and decide whether or not to deliver shock which helps the inexperienced nurse who has only just discovered a collapsed patient on the ward and so the analyser has different ECG waveforms to check the defib's responses.

Many defibs have the ability to show the ECG waveform on screen and even print out the waveform so the ECG simulators can be used to check the performance of these features. Inputting sine waves helps with checking that the filter response of the ECG circuit is correct (I even check the 50Hz notch filter routinely)

[calexanian]

The pretty brown board used in there is linen Phenolic board. Very common in old high voltage equipment. It is made of cotton linen fabric in a phenolic resin. Very strong electrically and mechanically.

As far as the resistors, Dave you have to get out more often. Some places i have worked those would be considered itty bitty! In the load bank for the 6303 rectifiers we use manny series panels of sheet style wire elements.

There are ribbon wound ones like this

 https://www.alibaba.com/product-detail/High-Power-Wire-Wound-Brake-Resistor_60084716939.html?spm=a2700.7724838.2017115.17.4OmekW

Then there are tubular high voltage ones.

http://www.kanthal.com/en/products/resistors-and-capacitors/bulk-ceramic-resistors/tubular-resistors/

And then anything from these guys!

http://www.cressall.com/

[bjcuizon]

They are standard snap connectors that can be attached to ECG leads of the defibrillator under test for cardiac scenario recognition.

Oh, so they're like the thing or locking mechanism on, let's say..a woman's wallet? Or like some coats?

[trophosphere]

They are standard snap connectors that can be attached to ECG leads of the defibrillator under test for cardiac scenario recognition.

Oh, so they're like the thing or locking mechanism on, let's say..a woman's wallet? Or like some coats?

Yes, they are common on wallets and clothing (see attachments). I realized that the connectors were the same as snap on buttons back when I was an undergrad in college about 12 years ago. It was for designing a single ECG patch that went on the chest and communicated wirelessly using Bluetooth.

[SeanB]

Same snap, made from plated steel on the disposable ones ( will last more than the shelf life when sterile and sealed away from oxygen) and the clip on the leads is made from 316l stainless, including the little spring wire clip used to grip the stud. The little cheap kits you buy at the haberdashery are perfect to make them, just use a small patch of wide self adhesive bandage ( and accept the burn on removal) with a small circle of cotton cloth and some KY jelly as conductor on the skin side, with the stud part through the bandage and cotton, riveted with the kit mandrel.