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Thread: Hammerhead controller vs mV cell readings

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    Hammerhead controller vs mV cell readings

    Hi,

    I have a slight problem with my Hammerhead controller (Rev C, single handset) to my MK15, I use Analytical "PSR-11-33-NM1" high output cells. And when I flush the loop at 6m I cant get higher PO2 reading then 1,3 - 1,4 and the mV reading donīt get higher then 156mV (all 3 cells stops at 156mV).

    I think that the cells are OK (have no possibility to check them in a pressure pot).

    Any body have any clever ideas?


    /Andreas

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    RBW Member horaceanddumpling is an unknown quantity at this point horaceanddumpling's Avatar
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    Re: Hammerhead controller vs mV cell readings

    Silly question, have you used the high output cells with the controller before, and is the controller for HO cells, seems odd that the output stops at an exact mv for all cells, sounds like a software issue, is it repeatable ? (just thinking that there's probably a voltage devider needed in the pod to use high output cells. Quick check with KJ time ?

    Whats the secondary saying ?

    I had a quick rummage on forum, we've been here before, sort of.

    http://www.rebreatherworld.com/showt...-vs-low-output


    Recon your controller is for standard cells, call Kevin time i think.

    Just a bit more thought, if you run a higher than usual setpoint i bet the controller will continually dose o2 into the loop, never reaching setpoint. It'll kill you. A 1.3 to 1.4 setpoint is bloody close to normal, if you'r cells are reading off somewhat, but within normal tolerances, i suspect the same will hapen. be carefull.
    Last edited by horaceanddumpling; 20th July 2015 at 11:13.

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    Re: Hammerhead controller vs mV cell readings

    Quote Originally Posted by horaceanddumpling  View Original Post
    Silly question, have you used the high output cells with the controller before, and is the controller for HO cells, seems odd that the output stops at an exact mv for all cells, sounds like a software issue, is it repeatable ? (just thinking that there's probably a voltage devider needed in the pod to use high output cells. Quick check with KJ time ?

    Whats the secondary saying ?

    I had a quick rummage on forum, we've been here before, sort of.

    http://www.rebreatherworld.com/showt...-vs-low-output


    Recon your controller is for standard cells, call Kevin time i think.

    Just a bit more thought, if you run a higher than usual setpoint i bet the controller will continually dose o2 into the loop, never reaching setpoint. It'll kill you. A 1.3 to 1.4 setpoint is bloody close to normal, if you'r cells are reading off somewhat, but within normal tolerances, i suspect the same will hapen. be carefull.

    Thanks for your reply,

    I've been diving it for more then 8 years with HO cells, so that's not the problem.
    This have occurred "over night", it worked all good last time I used it.

    I'll drop Kevin a mail and see if he have any clues.

    Since I noticed the PO2 on my way down and the cells was responding in normal time (except the limitation), I used 1.0 in setpoint and checked the mV reading frequently during the dive.

    The secundary was not connected, but can be an idea for next test.

    /A

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    Re: Hammerhead controller vs mV cell readings

    Is your controller a standard (cell 13 mv in air) controller or one modified for MK15 original-type high MV cell use? They have slight internal differences. Contact Keven.

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    RBW Member horaceanddumpling is an unknown quantity at this point horaceanddumpling's Avatar
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    Re: Hammerhead controller vs mV cell readings

    Hmm, ok, 156 mv on all three sensors is odd, kevin, and, it really does sound like the pod has the deviding resistors removed.

    O2 definetly 100% ?

    It's hard to flush to a real 100%,


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    Re: Hammerhead controller vs mV cell readings

    The Hammerhead Controller was designed for Low mV Sensors (like found in all other CCR's on the market). To work with the High Output Sensors, additional resistors are required in the circuit (usually located in the Pod on the MK 15 series).

    The only reason to use High Output Sensors on the Mark 15 is if you want to continue to use the Analog Secondary originally found on these systems. Some people have managed to wire in a different controller (like a Hammerhead) to the Secondary, in which case, you can use the "normal" output sensors found in other CCR's.

    Because of the design of the circuitry on the HH, the system is limited to a max of 156 mV (roughly a ppO2 of well over 3.00, which is even greater than the Mark 15 "2.00" limit found on the analog Secondary).

    Contact me directly, and we'll see if there's anything we need to change in your system.

    (kevin@rebreather.us)

    All the best,

    Kevin Juergensen
    Juergensen Marine, Inc.

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    Re: Hammerhead controller vs mV cell readings

    A "normal" R-22 type Sensor outputs around 40-55 mV in 100% Oxygen (a wide range that depends on the individual sensor, it's age, etc.). That translates to over 150 mV in 3.0 atm of O2 (a ppO2 of +3.00) all things being linear.

    A "normal" R-10D type Sensor outputs 114 mV in 100% Oxygen, which translates to ~350 mV in 3 atm of O2 (comparing apples to apples).

    That is why you need additional conditioning resistors if you intend to use a stock HH controller with R-10D type sensors.

    Kevin.

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    Re: Hammerhead controller vs mV cell readings

    Quote Originally Posted by heyydude  View Original Post

    The only reason to use High Output Sensors on the Mark 15 is if you want to continue to use the Analog Secondary originally found on these systems.
    I dont if I've just been lucky but I've also found the HO cells to be a hell of a lot more reliable than regular cells.

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