Prism Scrubber etc

**Steve** · 26th January 2007, 13:01

Quote: (Originally Posted by Dave Sutton)

With all due respect to a prior respondant, there is *no* value in watching the needle "jump rate" as the sensor is selected, again with all due respect that shows a lack of understanding of how a jeweled meter movement functions. All you are seeing is the mechanical aspect of the meter movement *itself*, IE the strength of the spring that returns the needle to zero when voltage is removed. The rate of the needle moving back to the measured position is again simply a mechanical spring function of the meter movement and has no bearing on cell viability. None, zero, zippo, nada, got it? If anyone was told otherwise by the OEM, it's a matter of simple salesmanship. Just ain't so. Not the first time that people promote what they happen to have on hand as a "design feature".....
Dave Sutton

Indeed. The manufacturer and users of jewelled meters really need to drop the whole ' I can see the quality of a cell by the speed the needle responds' line. It is just plain wrong.

Ken West · 26th January 2007, 14:42

Quote: (Originally Posted by Dave Sutton)

Teledyne sensors will work just fine. Nothing special about the SM stuff other than the fact that SM would like you to buy them.

The analog secondary WILL fail after you drop it. They work *just fine* and are well proven (being a copy of the Mark-15/CCR-1000 scheme) but they *will* break when dropped at their own cable length to the deck. Trust me on this. There are digital alternatives available from SARTEK and COLKAN. Either would be preferable. Change the battery once a year and forget about them. Analog needles are obsolete.

With all due respect to a prior respondant, there is *no* value in watching the needle "jump rate" as the sensor is selected, again with all due respect that shows a lack of understanding of how a jeweled meter movement functions. All you are seeing is the mechanical aspect of the meter movement *itself*, IE the strength of the spring that returns the needle to zero when voltage is removed. The rate of the needle moving back to the measured position is again simply a mechanical spring function of the meter movement and has no bearing on cell viability. None, zero, zippo, nada, got it? If anyone was told otherwise by the OEM, it's a matter of simple salesmanship. Just ain't so. Not the first time that people promote what they happen to have on hand as a "design feature".....

Opinion? The Prism is little more than a "serial manufactured homebuilt" with construction material selection and methods that are, err..... well let's say that I would be able to make a more robust rig in my garage. Electronics are simple and reliable, but there are other choices out there......

Dave Sutton

If thats the case then why is the response time variable. Why is it not exactly the same response time everytime?

Shas · 26th January 2007, 17:56

As the manufacturer I can assure you that the SMI sensors are proprietary and built under license for us and sold exclusively through us and our agents. The electronics were designed to match the sensors.

The secondary is also matched and the comment on watching the needle movement refers to when the meter is connected and reading a specific sensor - what you see is the needle movement matching the rise in mV output from the sensor and showing that reading - as sensors age the time to reach its output increases (especially for high PO2s as in calibration) and the lag between sensor response is evident to trained users.

The decision to use plastics was made as discussed in the scrubber article here - http://www.rebreatherworld.com/closed-circuit-rebreather-articles/6486-smi-scrubber.html.

WOB, weight and duration, along with tight and accurate electronic setpoint control was the overriding goal. The analog secondary gives us a completely power free option to verify function - the trade off is that you need to treat it like a camera or video - most customers try not to drop or throw their units around and for every one of the vocal individuals who were unable to work with that we have three who would have it no other way.

Bottom line - you do your research as the user and you chose based on what's important for you. Please bear in mind some of the people who post have vested interests - I do, and I'm tired of seeing people who have an axe to grind or grudge against us posting snide digs and BS which they can't substantiate or half truths which gloss over their part in it.

Best Wishes,
Shas

silent running · 26th January 2007, 18:47

Quote: (Originally Posted by Ken West)

If thats the case then why is the response time variable. Why is it not exactly the same response time everytime?

Well put, thanks Ken. If there's some other explanation for the fact that older sensors which have lower outputs always come up slower, I'd love to hear it. -Andy

silent running · 26th January 2007, 19:16

Quote: (Originally Posted by Dave Sutton)

The analog secondary WILL fail after you drop it. They work *just fine* and are well proven (being a copy of the Mark-15/CCR-1000 scheme) but they *will* break when dropped at their own cable length to the deck. Trust me on this.

Dave, my 2dry is 6 years old and still doing just fine and has been dropped plenty of times. Would it break if I dropped it a lot, sure. So would a VR3. Treat your gear nice and it will be nice to you. Also, it is well known that the older single jeweled movements were more fragile, just like the MK 2dry, also single movement, but in a metal housing. The new Prism 2dry is double movment and lighter than the MK 2dry and so more durable, they are an improvement. The digi ones are nice, but they are more expensive, need a battery, have a batery compartment/another seal, need to be turned on...

Quote: (Originally Posted by Dave Sutton)

With all due respect to a prior respondant, there is *no* value in watching the needle "jump rate" as the sensor is selected, again with all due respect that shows a lack of understanding of how a jeweled meter movement functions. All you are seeing is the mechanical aspect of the meter movement *itself*, IE the strength of the spring that returns the needle to zero when voltage is removed. The rate of the needle moving back to the measured position is again simply a mechanical spring function of the meter movement and has no bearing on cell viability.

I'm well aware that there's a spring on the needle and a weight. And the needle always drops back to 0 at the same rate because it's no longer under load. So I think you're half right. But it's the current coming off the cell that drives the needle up to the PO2 when the circuit is completed, which is why it does not rise from 0 at the same rate everytime and will give an indication of sensor output by the speed at which it climbs to the PO2. The sensor is additonally loaded by driving the needle and reflects this. And all this happens without having to wait for the solenoid to inject or having to do a dil flush. As I said, if there's some other explanation for what I'm seeing, everytime I watch the needle climb at a slower rate for the older sensors, I'd be glad to entertain the notion.

Drmike · 27th January 2007, 03:00

personally during a real dive with say a 30m EAD I cant differentiate (or far too busy diving to be able to check) the small relative differences in needle rising speed anyway. And who needs to? Who cares? You validate your sensors at 6m/1.6bar I dont care how fast or slow the needle rises or fails - thats indiactive sure but its not a direct measurement. What I care about is are they current limited to 1.6 - and relative (to the other cells) needle rising speed doesnt tell you that. O2 flush at 6m - forget about needle rising speed.

dive2dive2000 · 27th January 2007, 03:11

Quote: (Originally Posted by silent running)

Dave, my 2dry is 6 years old and still doing just fine and has been dropped plenty of times. Would it break if I dropped it a lot, sure. So would a VR3. Treat your gear nice and it will be nice to you. Also, it is well known that the older single jeweled movements were more fragile, just like the MK 2dry, also single movement, but in a metal housing. The new Prism 2dry is double movment and lighter than the MK 2dry and so more durable, they are an improvement. The digi ones are nice, but they are more expensive, need a battery, have a batery compartment/another seal, need to be turned on...

I'm well aware that there's a spring on the needle and a weight. And the needle always drops back to 0 at the same rate because it's no longer under load. So I think you're half right. But it's the current coming off the cell that drives the needle up to the PO2 when the circuit is completed, which is why it does not rise from 0 at the same rate everytime and will give an indication of sensor output by the speed at which it climbs to the PO2. The sensor is additonally loaded by driving the needle and reflects this. And all this happens without having to wait for the solenoid to inject or having to do a dil flush. As I said, if there's some other explanation for what I'm seeing, everytime I watch the needle climb at a slower rate for the older sensors, I'd be glad to entertain the notion.

Hi Andy,

There are Pros and Cons to everything, and when your diving in deep dark water sometimes the Pro and Con list can change sides

silent running · 27th January 2007, 09:57

Quote: (Originally Posted by Drmike)

personally during a real dive with say a 30m EAD I cant differentiate (or far too busy diving to be able to check) the small relative differences in needle rising speed anyway. And who needs to? Who cares? You validate your sensors at 6m/1.6bar I dont care how fast or slow the needle rises or fails - thats indiactive sure but its not a direct measurement. What I care about is are they current limited to 1.6 - and relative (to the other cells) needle rising speed doesnt tell you that. O2 flush at 6m - forget about needle rising speed.

Yes Mike, you're right the needle movement is indicative, but no substitute for the 6M test. Never said it was, I was mostly responding to those who insist that needle behavior doesn't tell you anything at all-not true. My point was always that it's good to have any additional info about sensor performance, no matter how minor. On the rare occaision that excess water has got on a sensor face, it may be voted out. If I check it on the 2dry and see that it's falling short of the other 2, knowing that it should be healthy and has passed high/low cal, I can reasonably guess that it might be water on the face. I aborted a dive because of this the first time, not knowing what it was. The next time it happened, I saw the sensor was reading low/came up slow, gave a good shake to the unit, water drops moved and the sensor came back on line. So the needle movement can be helpful, that's all.

Dave Sutton · 27th January 2007, 21:41

Quote: (Originally Posted by Drmike)

personally during a real dive with say a 30m EAD I cant differentiate (or far too busy diving to be able to check) the small relative differences in needle rising speed anyway. And who needs to? Who cares? You validate your sensors at 6m/1.6bar I dont care how fast or slow the needle rises or fails - thats indiactive sure but its not a direct measurement. What I care about is are they current limited to 1.6 - and relative (to the other cells) needle rising speed doesnt tell you that. O2 flush at 6m - forget about needle rising speed.

Well said.

Needles do work fine, *until dropped at the end of their cable to a steel ships deck* because a diver did not clip it off before sliding his rig off the dressing bench. Having broken several *exactly that way* in commercial use, I'd never use one again if I had a digital substitute. I'd drop any of the digitals the same distance and never worry about it.

Dave

jasonvds · 27th January 2007, 21:58

why use a needle display when you can use a digital one? why use an SMI cell when you can use a teledyne or an AII cell? Quite simple, as Dave said - salesmanship! Having been lucky enough to read Alex Deas' O2 cell study, my eyes have been opened greatly into alternatives and it's something that I've taken onboard in the new sets we're building...

There are loads of cells out there that give all sorts of performance from mV output to response time, explore alternatives and don't accept manufacturers words as gospel.

right that's enough

for me.

26th January 2007, 13:01	#11 (permalink)
Steve Ladies bring a plate Current Rebreather/s: Megalodon Home Build Other Rebreather/s: Not Bought Yet Inspiration Classic Sport Kiss Classic Kiss MK 15.X Home Build Join Date: Feb 2005 Location: Perth - Australia Posts: 1,100	Re: Prism Scrubber etc Quote: (Originally Posted by Dave Sutton) With all due respect to a prior respondant, there is no value in watching the needle "jump rate" as the sensor is selected, again with all due respect that shows a lack of understanding of how a jeweled meter movement functions. All you are seeing is the mechanical aspect of the meter movement itself, IE the strength of the spring that returns the needle to zero when voltage is removed. The rate of the needle moving back to the measured position is again simply a mechanical spring function of the meter movement and has no bearing on cell viability. None, zero, zippo, nada, got it? If anyone was told otherwise by the OEM, it's a matter of simple salesmanship. Just ain't so. Not the first time that people promote what they happen to have on hand as a "design feature"..... Dave Sutton Indeed. The manufacturer and users of jewelled meters really need to drop the whole ' I can see the quality of a cell by the speed the needle responds' line. It is just plain wrong. __________________ WARNING: I contain occasional coarse language, extreme sexual references, nudity, and adult themes, which may offend some people - Usually churchy types.
(Offline)

26th January 2007, 14:42	#12 (permalink)
Ken West New Member Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: Feb 2006 Posts: 23	Re: Prism Scrubber etc Quote: (Originally Posted by Dave Sutton) Teledyne sensors will work just fine. Nothing special about the SM stuff other than the fact that SM would like you to buy them. The analog secondary WILL fail after you drop it. They work just fine and are well proven (being a copy of the Mark-15/CCR-1000 scheme) but they will break when dropped at their own cable length to the deck. Trust me on this. There are digital alternatives available from SARTEK and COLKAN. Either would be preferable. Change the battery once a year and forget about them. Analog needles are obsolete. With all due respect to a prior respondant, there is no value in watching the needle "jump rate" as the sensor is selected, again with all due respect that shows a lack of understanding of how a jeweled meter movement functions. All you are seeing is the mechanical aspect of the meter movement itself, IE the strength of the spring that returns the needle to zero when voltage is removed. The rate of the needle moving back to the measured position is again simply a mechanical spring function of the meter movement and has no bearing on cell viability. None, zero, zippo, nada, got it? If anyone was told otherwise by the OEM, it's a matter of simple salesmanship. Just ain't so. Not the first time that people promote what they happen to have on hand as a "design feature"..... Opinion? The Prism is little more than a "serial manufactured homebuilt" with construction material selection and methods that are, err..... well let's say that I would be able to make a more robust rig in my garage. Electronics are simple and reliable, but there are other choices out there...... Dave Sutton If thats the case then why is the response time variable. Why is it not exactly the same response time everytime?
(Offline)

26th January 2007, 17:56	#13 (permalink)
Shas New Member Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: Mar 2005 Location: Lebanon, TN Posts: 12	Re: Prism Scrubber etc As the manufacturer I can assure you that the SMI sensors are proprietary and built under license for us and sold exclusively through us and our agents. The electronics were designed to match the sensors. The secondary is also matched and the comment on watching the needle movement refers to when the meter is connected and reading a specific sensor - what you see is the needle movement matching the rise in mV output from the sensor and showing that reading - as sensors age the time to reach its output increases (especially for high PO2s as in calibration) and the lag between sensor response is evident to trained users. The decision to use plastics was made as discussed in the scrubber article here - http://www.rebreatherworld.com/closed-circuit-rebreather-articles/6486-smi-scrubber.html. WOB, weight and duration, along with tight and accurate electronic setpoint control was the overriding goal. The analog secondary gives us a completely power free option to verify function - the trade off is that you need to treat it like a camera or video - most customers try not to drop or throw their units around and for every one of the vocal individuals who were unable to work with that we have three who would have it no other way. Bottom line - you do your research as the user and you chose based on what's important for you. Please bear in mind some of the people who post have vested interests - I do, and I'm tired of seeing people who have an axe to grind or grudge against us posting snide digs and BS which they can't substantiate or half truths which gloss over their part in it. Best Wishes, Shas
(Offline)

26th January 2007, 18:47	#14 (permalink)
silent running Mature mouth breather Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: Jun 2005 Location: U.S.A. Brooklyn, New York Posts: 1,813	Re: Prism Scrubber etc Quote: (Originally Posted by Ken West) If thats the case then why is the response time variable. Why is it not exactly the same response time everytime? Well put, thanks Ken. If there's some other explanation for the fact that older sensors which have lower outputs always come up slower, I'd love to hear it. -Andy
(Offline)

26th January 2007, 19:16	#15 (permalink)
silent running Mature mouth breather Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: Jun 2005 Location: U.S.A. Brooklyn, New York Posts: 1,813	Re: Prism Scrubber etc Quote: (Originally Posted by Dave Sutton) The analog secondary WILL fail after you drop it. They work just fine and are well proven (being a copy of the Mark-15/CCR-1000 scheme) but they will break when dropped at their own cable length to the deck. Trust me on this. Dave, my 2dry is 6 years old and still doing just fine and has been dropped plenty of times. Would it break if I dropped it a lot, sure. So would a VR3. Treat your gear nice and it will be nice to you. Also, it is well known that the older single jeweled movements were more fragile, just like the MK 2dry, also single movement, but in a metal housing. The new Prism 2dry is double movment and lighter than the MK 2dry and so more durable, they are an improvement. The digi ones are nice, but they are more expensive, need a battery, have a batery compartment/another seal, need to be turned on... Quote: (Originally Posted by Dave Sutton) With all due respect to a prior respondant, there is no value in watching the needle "jump rate" as the sensor is selected, again with all due respect that shows a lack of understanding of how a jeweled meter movement functions. All you are seeing is the mechanical aspect of the meter movement itself, IE the strength of the spring that returns the needle to zero when voltage is removed. The rate of the needle moving back to the measured position is again simply a mechanical spring function of the meter movement and has no bearing on cell viability. I'm well aware that there's a spring on the needle and a weight. And the needle always drops back to 0 at the same rate because it's no longer under load. So I think you're half right. But it's the current coming off the cell that drives the needle up to the PO2 when the circuit is completed, which is why it does not rise from 0 at the same rate everytime and will give an indication of sensor output by the speed at which it climbs to the PO2. The sensor is additonally loaded by driving the needle and reflects this. And all this happens without having to wait for the solenoid to inject or having to do a dil flush. As I said, if there's some other explanation for what I'm seeing, everytime I watch the needle climb at a slower rate for the older sensors, I'd be glad to entertain the notion.
(Offline)

27th January 2007, 03:00	#16 (permalink)
Drmike Custom Title Allowed! Current Rebreather/s: MK 15.X Ouroboros Other CCR Home Build Other Rebreather/s: Inspiration Classic Other CCR Home Build Join Date: Feb 2005 Posts: 3,157	Re: Prism Scrubber etc personally during a real dive with say a 30m EAD I cant differentiate (or far too busy diving to be able to check) the small relative differences in needle rising speed anyway. And who needs to? Who cares? You validate your sensors at 6m/1.6bar I dont care how fast or slow the needle rises or fails - thats indiactive sure but its not a direct measurement. What I care about is are they current limited to 1.6 - and relative (to the other cells) needle rising speed doesnt tell you that. O2 flush at 6m - forget about needle rising speed. __________________ Cave diving is a sport Wreck diving is a sport Diving in general is a sport 'Rebreather diving' is not a sport its the delusional obsession with a highly dangerous and often inappropriate piece of equipment
(Offline)

27th January 2007, 03:11	#17 (permalink)
dive2dive2000 PRISM DIVER & LUVIN IT! Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: Feb 2005 Location: Long Island, NY Posts: 788	Re: Prism Scrubber etc Quote: (Originally Posted by silent running) Dave, my 2dry is 6 years old and still doing just fine and has been dropped plenty of times. Would it break if I dropped it a lot, sure. So would a VR3. Treat your gear nice and it will be nice to you. Also, it is well known that the older single jeweled movements were more fragile, just like the MK 2dry, also single movement, but in a metal housing. The new Prism 2dry is double movment and lighter than the MK 2dry and so more durable, they are an improvement. The digi ones are nice, but they are more expensive, need a battery, have a batery compartment/another seal, need to be turned on... I'm well aware that there's a spring on the needle and a weight. And the needle always drops back to 0 at the same rate because it's no longer under load. So I think you're half right. But it's the current coming off the cell that drives the needle up to the PO2 when the circuit is completed, which is why it does not rise from 0 at the same rate everytime and will give an indication of sensor output by the speed at which it climbs to the PO2. The sensor is additonally loaded by driving the needle and reflects this. And all this happens without having to wait for the solenoid to inject or having to do a dil flush. As I said, if there's some other explanation for what I'm seeing, everytime I watch the needle climb at a slower rate for the older sensors, I'd be glad to entertain the notion. Hi Andy, There are Pros and Cons to everything, and when your diving in deep dark water sometimes the Pro and Con list can change sides __________________ Safe Diving, Martin "but what's the fun of getting what you need, instead of what you want?"
(Offline)

27th January 2007, 09:57	#18 (permalink)
silent running Mature mouth breather Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: Jun 2005 Location: U.S.A. Brooklyn, New York Posts: 1,813	Re: Prism Scrubber etc Quote: (Originally Posted by Drmike) personally during a real dive with say a 30m EAD I cant differentiate (or far too busy diving to be able to check) the small relative differences in needle rising speed anyway. And who needs to? Who cares? You validate your sensors at 6m/1.6bar I dont care how fast or slow the needle rises or fails - thats indiactive sure but its not a direct measurement. What I care about is are they current limited to 1.6 - and relative (to the other cells) needle rising speed doesnt tell you that. O2 flush at 6m - forget about needle rising speed. Yes Mike, you're right the needle movement is indicative, but no substitute for the 6M test. Never said it was, I was mostly responding to those who insist that needle behavior doesn't tell you anything at all-not true. My point was always that it's good to have any additional info about sensor performance, no matter how minor. On the rare occaision that excess water has got on a sensor face, it may be voted out. If I check it on the 2dry and see that it's falling short of the other 2, knowing that it should be healthy and has passed high/low cal, I can reasonably guess that it might be water on the face. I aborted a dive because of this the first time, not knowing what it was. The next time it happened, I saw the sensor was reading low/came up slow, gave a good shake to the unit, water drops moved and the sensor came back on line. So the needle movement can be helpful, that's all.
(Offline)

27th January 2007, 21:41	#19 (permalink)
Dave Sutton Membership Cancelled Current Rebreather/s: Sport Kiss MK 15.X rEvo Other CCR Azimuth Home Build Other Rebreather/s: Classic Kiss rEvo Other CCR Azimuth Home Build Join Date: Jun 2006 Location: Narragansett, Rhode Island and Hackettstown, New Jersey Posts: 2,637	Re: Prism Scrubber etc Quote: (Originally Posted by Drmike) personally during a real dive with say a 30m EAD I cant differentiate (or far too busy diving to be able to check) the small relative differences in needle rising speed anyway. And who needs to? Who cares? You validate your sensors at 6m/1.6bar I dont care how fast or slow the needle rises or fails - thats indiactive sure but its not a direct measurement. What I care about is are they current limited to 1.6 - and relative (to the other cells) needle rising speed doesnt tell you that. O2 flush at 6m - forget about needle rising speed. Well said. Needles do work fine, until dropped at the end of their cable to a steel ships deck because a diver did not clip it off before sliding his rig off the dressing bench. Having broken several exactly that way in commercial use, I'd never use one again if I had a digital substitute. I'd drop any of the digitals the same distance and never worry about it. Dave
(Offline)

27th January 2007, 21:58	#20 (permalink)
jasonvds New Member Current Rebreather/s: Other CCR Dolphin Ray Other SCR Other Rebreather/s: Other CCR Dolphin Ray Other SCR Join Date: Jan 2006 Location: Sydney, Australia Posts: 88	Re: Prism Scrubber etc why use a needle display when you can use a digital one? why use an SMI cell when you can use a teledyne or an AII cell? Quite simple, as Dave said - salesmanship! Having been lucky enough to read Alex Deas' O2 cell study, my eyes have been opened greatly into alternatives and it's something that I've taken onboard in the new sets we're building... There are loads of cells out there that give all sorts of performance from mV output to response time, explore alternatives and don't accept manufacturers words as gospel. right that's enough for me.
(Offline)

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode