HH Abnormality

sensor330 · 20th June 2006, 02:19

Well I've found a interesting problem and I would like to see if anyone can replicate it. Well my sensors were disconnected I noticed there was still a MV of 1 on the sensor 1 and 2 position on the primary and the 2 position on the secondary was blinking 1 on and off. I then placed my secondary close to my primary and noticed the the MV reading on the primary spiked and I got a reading of 2 3 3 and 3 4 4 on the secondary. If I were to hold the handsets together I could get a reading of 4 5 5 on the primary and 8 9 8 on the secondary. I then went back to the screen that displays the PO2 and if I held them together I could get a PO2 reading as high as 0.9 with no O2 cells in the HH! I don't think I'll be using my HH again until this is sorted out so I guess for now I have a $3500 paper weight.

Scott

**JPJones** · 20th June 2006, 02:30

Scott mine will do it also but with the circuit open it will do things like that it's just stray voltage. Take any volt meter and it will do the same thing.

Underwaterbear · 20th June 2006, 02:39

Quote: (Originally Posted by JPJones)

Scott mine will do it also but with the circuit open it will do things like that it's just stray voltage. Take any volt meter and it will do the same thing.

You should really get 0V if you wear gloves, but otherwise your body will provide some voltage. I'm good for about 44mV and interestingly my left hand is positive.

sensor330 · 20th June 2006, 03:01

Quote: (Originally Posted by JPJones)

Scott mine will do it also but with the circuit open it will do things like that it's just stray voltage. Take any volt meter and it will do the same thing.

I guess I'm a dumb ass when it comes to electronics. My primary and secondary MV readings are still not matching up though.

Scuba_Vixen · 20th June 2006, 03:02

It's much like in the old days of turntables, if you removed the cartrige, you got that nasty hum from the stray AC voltage being amplified by the high gain amp circuits.

Put in the cartrige, or short the input to ground, and all was quiet again. Short the sensor plugs with pieces of wire and look for 0's then, not while they are open circuit.

Darlene

***jradomski*** · 20th June 2006, 03:07

Quote: (Originally Posted by Underwaterbear)

You should really get 0V if you wear gloves, but otherwise your body will provide some voltage. I'm good for about 44mV and interestingly my left hand is positive.

Exactly..

Diffenent designs isolate differently.. the way the HH is isolated a disconnected sensor is basically a high gain antenna and will pick up any stray electrical charge wheether it be from a body,the solenoid firing, or from an induced magnetic filed..... (this arrangement really keeps the sides isolated in case of a short).
This effect will be totally different in water since everything will be at the same potential..
if you really want to see what it looks like, short the leads to really give it a 0 to read..

**wedivebc** · 20th June 2006, 03:34

why does HH not put a load resistor across the cells so you will get a zero reading (as opposed to noise) if the sensor accidently gets disconnected? Seems like a pretty easy fix.

***jradomski*** · 20th June 2006, 03:49

Quote: (Originally Posted by wedivebc)

why does HH not put a load resistor across the cells so you will get a zero reading (as opposed to noise) if the sensor accidently gets disconnected? Seems like a pretty easy fix.

I guess its a design choice.. I can think of pros and cons both ways..
It really depends on if the sensors are being used as differential sensors or a common ground..

A "floating" sensor really isnt going to be a problem since it will be different from the others and get voted out.. It all comes down to design trade offs..

20th June 2006, 02:19	#1 (permalink)
sensor330 RBW Member Current Rebreather/s: Megalodon Other Rebreather/s: Not Bought Yet Inspiration Classic Join Date: Feb 2005 Location: Victoria, British Columbia, Canada Posts: 594	HH Abnormality Well I've found a interesting problem and I would like to see if anyone can replicate it. Well my sensors were disconnected I noticed there was still a MV of 1 on the sensor 1 and 2 position on the primary and the 2 position on the secondary was blinking 1 on and off. I then placed my secondary close to my primary and noticed the the MV reading on the primary spiked and I got a reading of 2 3 3 and 3 4 4 on the secondary. If I were to hold the handsets together I could get a reading of 4 5 5 on the primary and 8 9 8 on the secondary. I then went back to the screen that displays the PO2 and if I held them together I could get a PO2 reading as high as 0.9 with no O2 cells in the HH! I don't think I'll be using my HH again until this is sorted out so I guess for now I have a $3500 paper weight. Scott
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20th June 2006, 02:30	#2 (permalink)
JPJones O2ptima Test Dummy Current Rebreather/s: Inspiration Classic Megalodon Sport Kiss Classic Kiss Optima Titan Other Rebreather/s: Join Date: Sep 2005 Location: Florida Posts: 367	Re: HH Abnormality Scott mine will do it also but with the circuit open it will do things like that it's just stray voltage. Take any volt meter and it will do the same thing. __________________ NSS/CDS Training Chairman www.jpjscuba.com
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20th June 2006, 02:39	#3 (permalink)
Underwaterbear A Prismer in Megland Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: May 2005 Location: Seattle, WA Posts: 198	Re: HH Abnormality Quote: (Originally Posted by JPJones) Scott mine will do it also but with the circuit open it will do things like that it's just stray voltage. Take any volt meter and it will do the same thing. You should really get 0V if you wear gloves, but otherwise your body will provide some voltage. I'm good for about 44mV and interestingly my left hand is positive.
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20th June 2006, 03:01	#4 (permalink)
sensor330 RBW Member Current Rebreather/s: Megalodon Other Rebreather/s: Not Bought Yet Inspiration Classic Join Date: Feb 2005 Location: Victoria, British Columbia, Canada Posts: 594	Re: HH Abnormality Quote: (Originally Posted by JPJones) Scott mine will do it also but with the circuit open it will do things like that it's just stray voltage. Take any volt meter and it will do the same thing. I guess I'm a dumb ass when it comes to electronics. My primary and secondary MV readings are still not matching up though.
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20th June 2006, 03:02	#5 (permalink)
Scuba_Vixen e/mCCR Dolphin Pilot Current Rebreather/s: Other CCR Home Build Other Rebreather/s: Other CCR Home Build Join Date: May 2005 Location: St. Croix USVI Posts: 557	Re: HH Abnormality It's much like in the old days of turntables, if you removed the cartrige, you got that nasty hum from the stray AC voltage being amplified by the high gain amp circuits. Put in the cartrige, or short the input to ground, and all was quiet again. Short the sensor plugs with pieces of wire and look for 0's then, not while they are open circuit. Darlene
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20th June 2006, 03:07	#6 (permalink)
*jradomski* Moderator Current Rebreather/s: Inspiration Classic Sport Kiss Optima rEvo Other CCR Other Rebreather/s: Inspiration Vision Evolution Megalodon Classic Kiss rEvo Other CCR Join Date: Mar 2005 Location: "Da" Bronx Posts: 3,113	Re: HH Abnormality Quote: (Originally Posted by Underwaterbear) You should really get 0V if you wear gloves, but otherwise your body will provide some voltage. I'm good for about 44mV and interestingly my left hand is positive. Exactly.. Diffenent designs isolate differently.. the way the HH is isolated a disconnected sensor is basically a high gain antenna and will pick up any stray electrical charge wheether it be from a body,the solenoid firing, or from an induced magnetic filed..... (this arrangement really keeps the sides isolated in case of a short). This effect will be totally different in water since everything will be at the same potential.. if you really want to see what it looks like, short the leads to really give it a 0 to read.. __________________ Joe Radomski CCR Trimix Instructor Trainer ANDI Instructor Trainer Director #10 All posts are personal opinions and DO NOT reflect any affiliated agency unless specifically stated.
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20th June 2006, 03:34	#7 (permalink)
wedivebc Dave Tomblin Current Rebreather/s: Megalodon Other CCR Other Rebreather/s: Not Bought Yet Inspiration Classic Sport Kiss Other CCR Join Date: Feb 2005 Location: Vancouver Island BC Canada Posts: 1,507	Re: HH Abnormality why does HH not put a load resistor across the cells so you will get a zero reading (as opposed to noise) if the sensor accidently gets disconnected? Seems like a pretty easy fix. __________________ Cheers, Dave.... Man is the only animal burdened with the knowledge he will eventually die
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20th June 2006, 03:49	#8 (permalink)
*jradomski* Moderator Current Rebreather/s: Inspiration Classic Sport Kiss Optima rEvo Other CCR Other Rebreather/s: Inspiration Vision Evolution Megalodon Classic Kiss rEvo Other CCR Join Date: Mar 2005 Location: "Da" Bronx Posts: 3,113	Re: HH Abnormality Quote: (Originally Posted by wedivebc) why does HH not put a load resistor across the cells so you will get a zero reading (as opposed to noise) if the sensor accidently gets disconnected? Seems like a pretty easy fix. I guess its a design choice.. I can think of pros and cons both ways.. It really depends on if the sensors are being used as differential sensors or a common ground.. A "floating" sensor really isnt going to be a problem since it will be different from the others and get voted out.. It all comes down to design trade offs.. __________________ Joe Radomski CCR Trimix Instructor Trainer ANDI Instructor Trainer Director #10 All posts are personal opinions and DO NOT reflect any affiliated agency unless specifically stated.
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