My head problems an update :(

uri

Mark - I am an electrical engineer and I can tell you that the presence of the HUD wired in in this manner is:
1. Extra impedance on the circuit;
2. Unreliable wiring

So if you are APD, who has done a lot of testing and CE certification, what would your position be on this ? It is a no-brainer.

Guy




The input impedance of the circuitry is way higher than that. Anyone who knows anything about practical design engineering and Oxygen cells should realise that in general, there is a tolerance on termination resistor values of say 1%. That means that there is a quite acceptable variance of 100ohms on a 10k termination resistor. This is equivalent to a load change of about 70nanoamps on the cells for a 70mV output. If 70nanoamps is acceptable then why is an additional load of tens of picoamps caused by a HUD unacceptable?

Admittedly, the inspo I believe has cells terminated by 5k not 10k but this doesn't change the basis of the argument and it's possible that other leakage currents from imperfect wire insulators are bigger than the input leakage to the circuitry but it will not be significant if the wires are suitably
insulated and waterproofed which they are. As for unreliable wiring, wiring is as unreliable as it is built to be and if put together correctly, it's about as unreliable as APD's current wiring. There's a very simple test, calibrate the unit ,watch the cell outputs, connect the Hud in, see if there's any change. Don't listen to me, ask my customers if there is?



rgds

Uri

PS It's also worth mentioning that any Rebreather with my Hud attached is no longer CE approved and if a head is sent in for repair, there is no Hud attached, just some t pieces that are open circuit until the Hud is attached. If one wants to blame a few inches of open circuit wire and a T-piece on Mark's symptoms, it's stretching the bounds of credibility.

divetheworld

Regarding your last statement let me be clear by qualifying my position. I am an appointed body under the New Approach directives and our company is a Notified Body under such.
A simplified explanation - CE marking is the responsibility of the manufacturer who is providing equipment in the European Economic Area to ensure it complies when first provided for use. If equipment is modified to change its function or performance then the person who makes those changes is legally responsible for the new assembly. Unless that equipment is being used by AP in the course of their business by an employee for the purposes of diving operations, then they have no responsibility under the regulations. There is no law which requires individuals to maintain the conformity status of equipment which is not used in the course of a business.

Ergo, and defacto, CE is not their problem. Morally, they might see it a different way especially if they consider themselves liable if there is a potential problem.

Brent.

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