Sensor test Diverite Liberty, which deviation is acceptable?

[Agro]

I have not beeing diving the Liberty for 4 month. Today I made the sensor pressure test, 1 to 3.5 bar pressure. Liberty shows deviation of ideal numbers, I had a max of 8% at 3.5 bar.

My old manual sais 7% is the max allowed deviation. Is this still Divesoft's recommendation? I found no information on Divesoft's website. Am I blind?

As far as I know sensors "go to sleep" if they have not been used for a long time. I must wake them up by exposing to oxygen for some time. I guess a sensor test at 3.5 bar is a perfect wake up. But can I trust this first test or must it be repeated?

I thinks I will keep the sensors at 1 bar of oxygen for 24 hours and then repeat the sensor test. What do you think about it?

Sensors are 8 month old.

 

[makar0n]

Some great reading (attached PDF) here, might be helpful re deviation:

Question Post in thread 'O2 sensor calibration'

Jul 7, 2025

Don't you need to know what MV the cells calibrate to in O2 to do this? Say you have 3 cells and they read 42 mv, 50 mv and 57 mv to start with (at surface) duing o2 calibration.

How do you remember on the dive what the cells started at and which cells had the assigned value? How do you know during the dive that the cells don't drift with temperature change. How can a combination of cell drift and poor memory, make an real sense of the during a dive?

My mental maths level approximates that of a 3 year old, whilst diving at any depth below 6m.

im assuming you check your MV reading...

• lermontov

 

[Agro]

Some great reading (attached PDF) here, might be helpful re deviation:

Question Post in thread 'O2 sensor calibration'

Jul 7, 2025

Don't you need to know what MV the cells calibrate to in O2 to do this? Say you have 3 cells and they read 42 mv, 50 mv and 57 mv to start with (at surface) duing o2 calibration.

How do you remember on the dive what the cells started at and which cells had the assigned value? How do you know during the dive that the cells don't drift with temperature change. How can a combination of cell drift and poor memory, make an real sense of the during a dive?

My mental maths level approximates that of a 3 year old, whilst diving at any depth below 6m.

im assuming you check your MV reading...

• lermontov

Well, some interessting points but unfortunately not the answers to my questions.

 

[piranhaman00]

Im very new to RB but why would you test up to 3.5 bar? Any deviation past approx 2.0 bar is meaningless. If your sensors are linear to 1.6 bar you are good to go.

Keeping them exposed to 1 bar to 'wake them up' will kill the life span also. Mine 'woke up' by air exposure for a few days.

 

[LFMarm]

Liberty shows deviation of ideal numbers, I had a max of 8% at 3.5 bar.

Interesting that the test goes this far out of the working range. Given that the highest you typically dive is 1.6, I would assume that non linearity beyond 2.0 is not so relevant. How are the 3.5 readings used? Just compared to an expected deviation or used to predict deviation in the working range of 0.5-1.6?

 

[Agro]

1 bar pO2=50mV
3 bar pO2 should be 150mV
In reality 3 bar pO2 is 135mV, so deviation is 10%
Reference is always measurement at 1 bar

A new sensor is linear up to 3.5 bar. After for ex. 18 month it is linear up to 2 bar and not linear anymore at 3 bar. After for ex. 20 month it is linear up to 1.5 bar and not linear at 2 bar.

Testing at 3.5 bar gives you a good information about sensor's shape.

 

[rjack321]

Testing at 3.5 bar gives you a good information about sensor's shape.

If the cell is linear at 2 and non-linear at 3 bar that cell is fine. Testing way up at 3.5 bar is not useful information.

 

[Agro]

If the cell is linear at 2 and non-linear at 3 bar that cell is fine. Testing way up at 3.5 bar is not useful information.

No, that's wrong.

 

[rjack321]

No, that's wrong.

Every galvanic cell ever made will lose linearity at 3.5 at some time, some won't even get there new out of the box. That tells you nothing about it's fitness for use below 2.0.