Prism Topaz - Analog Secondary & Cell Sensors

ChettL

Prism Topaz - Analog Secondary & Cell Sensors

Most Prism Topaz owners know that the Analog Secondary is delicate, and carry the secondary in some type of protective packing during travel from the home to diving in the water. I carry mine in a small Pelican box with foam around it. I have been told that during transport it’s best to keep the Secondary Dial Knob on a sensor (either 1,2 or 3) so that the needle is reading Air (0.21), so that if the secondary gets banged or knocked hard, the jewels attached to the needle movement would stand a better chance of not getting damaged as opposed to the needle sitting at zero. The question I have is this: during storage, when the rebreather is put away and not being used, is it best to leave the Analog Secondary on sensor 1,2, or 3? It seems to me that this puts a load (current drain) on the Sensor chosen. I would think that it would be better to put the Analog Secondary on “Set Point” during storage so that there is no load on any of the Sensors.

Chett.L

caveseeker7

Should have been covered during class, leave it on #2.
If the knob gets knocked in either direction there'll be another sensor.

Simple math, really:
A sensor costs $75, a new secondary $450 (last I checked, anyway).
Replacing a sensor should take no more than a couple of days, probably next day in MDR.
Replacing a secondary can take weeks, if not months.

So even if there's an appreciable use of the sensor, you rather want to get a new one than a new gauge.

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DaveC

As already stated, the load is very minimal and should be kept on sensor 2. If on either the set point or battery setting and the secondary gets knocked, then it could jar the secondary enough to jump the needle. In the case is a good idea unless you know there won't be any knock where its being stored. I always keep mine in the storage box because one just never knows.

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ChettL

Hi Stephen,

This was totally covered in my class and I know that the Secondary should be on Sensor (2) during transport, however, during storage, if the rig is secure in a Pelican Box, Storm Case or UK case and this case does not get moved, what about putting the Secondary on Set Point so that it does not draw any current off the sensor? If there is a period that I do not use the rig for a month or two it seams like the sensor would last longer?

Chett.L

Lake_Tahoe_Diver

I look at it this way, store it set on senor 2 and then you do not have to worry about it being bumped, moved, etc by someone else. Save you self the cost of the new display and the 3 - 6 month wait to get a replacement.

We are not talking about reducing the cells life by a period of months, it will be some where around a period of weeks. So I do not see why you are concern about shorting the life of the cell, after all you should be planning on getting new cells every 12 months or so just in case.

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Steve

The current should be micro amps, just find out the value of the shunt resister and work it out.*













* Nothing would surprise me with regard to material selection on the PRISM

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DeepBlueInnovation

Did I hear that ISC are making a plastic can for the Meg? Don't worry, I am sure it will be more reliable than the Prism...

Mike

Just want to make sure of something here. While it's in it's small pelican box, it is still connected to the Prism head isn't it? I assume you know this, but if it's not connected, there is no load on it...

SMI short out a couple of pins on the secondary when it's disconnected from the head and transport it that way (not that I can remember which pins off hand)

As for worrying about aging one cell more than the others; don't worry about it. I've tracked voltage on the cells over time and cell 2 hasn't fallen faster than the others. (And if you still wnt to worry about it, just swap cells from position to position every 3 months or so, then they will degrade 'evenly')

Mike

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warjarrett

Leaving the secondary on position 2 was covered on the first day of my training. But on each subsequent day, I was taught to ask questions, think for myself, and continue to grow in my understanding of safety and equipment maintenance. I was NEVER taught to blindly follow rules-of-thumb without understanding why. So, yes, if the secondary gets jostled, its mechanism is better protected from damage in one of the three positions 1, 2 or 3. There is NO REASON to always leave it on 2. Position 1 or 3 is just as good for protection, and changing this position occasionally will allow you to more evenly age the sensors, without having to switch sensors around inside the head. But my slightly greater knowledge now (compared to graduation day), that I have achieved from continuing to think for myself AFTER training AGREES with Chett's suggestion: as long as you are only storing the rebreather, there is no reason to stress an oxygen sensor by leaving one under load from the secondary. There is very good reason to switch the secondary to S, if the unit is to be stored for a while. Just dont forget to switch it to a sensor position before transporting it. Now, does anyone really disagree with this?

DeepBlueInnovation

Walk over to your unit, switch the analogue secondary to set point and switch the electronics on. You will notice that the needle moves from reading zero to whatever setpoint is. Now turn the electronics off and you will notice the needle returns to zero. Now bearing in mind that the needle must not be resting at zero if it is to be protected it must not be at zero so...

why would you put it on set point to protect it?

Up until this point I have thought that others criticizing your posts have been unfairly harsh, but I am starting to think you shouldn't be on CCR. By all means question, but you haven't paid attention to what others have written. It does not appear that you have understood the most basic instructions from your course or that you have the capacity for reasoned thought.

If you cannot grasp this most fundamental of concepts, how are you going to survive in an emergency situation WHEN something goes wrong.

No one wants any more fatalities.

Ben.