Boston Breakwater
"Outlaw." Solo Diver
Hello, Everyone. I'm in the market for an O2 analyzer. I have been scouring the Internet looking at different companies. Admittedly, I don't know if one company is more reputable than another, or anything about their customer service?
I will use it for "Nitrox." mixes Typically 24% and 26% ranging up to 50% (Sometimes 80%)
I am generally alone, and sometimes in remote locations, so, I would also like to double check, and verify my Oxygen bottles. (Preferably one that would screw right into the D.I.N. valve.)
I was leaning towards this.
OxyCheq Expedition O2 Analyzer
I would greatly appreciate your feedback..........Personal experience, and recommendations.
Edit. When. I typed "The Best."........I realized there may be models way beyond my necessity. I would like to stay in the $300 - $500.00 range. (If, possible.)
Edit. I would almost expect the reading to go from 0% to 100% (Is that not the case?)
Cheers.
How to Find the Best Scuba Oxygen Analyzer - Scuba Diving Gear
A Must Have for Nitrox Divers: Undercurrent 02/2009
Excerpt.
Analyzer Calibration
A Nitrox analyser has an oxygen sensor that generates a voltage that varies according to the percentage of oxygen present, and gives a readout on a voltmeter calibrated in percentages. An analyzer reading is affected by air pressure (weather) and the aging of the sensor cell, so before each dive, it needs to be calibrated at 20.9 percent O2 with clean air passing around it. If you calibrate using pure oxygen instead of air, the sensor readings will be three times more accurate.
Recently, I was on a liveaboard with a diver who was a gas analyst from Siemens. He merely checked his tank each time to see that he didn’t have air. He told me that the analyzer on board was so inaccurate, it was only good for telling whether you got air or something else, but nothing more. He just checked to see if it went over 21 percent but didn’t bother with a final reading. Furthermore, he said, the little oxygen analyzer that I had held so much faith in was almost totally inaccurate. I was shocked. So what was wrong with the simple equipment that was available to us?
The problem stems from gas flowing over the sensor. He pointed out that the gas had to be stationary or controlled to a known rate. By simply increasing the flow, the apparent oxygen content increased. Cracking open a tank valve “just a little’” and holding the cell over it is evidently not accurate enough for him. Temperature also makes a difference, and gas depressurizing from a tank can be very cold.
Some analyzers use the direct-feed hose to the BC, using the regulator first-stage as a flow control. It takes time to get a reading and this seems unpopular with divers impatient to get in the water. Divers will always look for the most convenient method. I have witnessed Nitrox being analyzed by holding the sensor in the mouthpiece of a regulator while the purge button was pressed.
But manufacturers have come up with designs to get a stationary sample of gas at the same ambient temperature and pressure with which the analyzer was calibrated. Some restrict the flow of gas over the cell while others attempt to capture a stationary sample. It seems that the bit of plastic tube that interfaces between the tank valve and the sensor is very important.
If your Nitrox is made by the older partial pressure blending system, you need to know your analyzer is exact, because there you may inadvertently get very high percentages of oxygen, if by mistake.
I will use it for "Nitrox." mixes Typically 24% and 26% ranging up to 50% (Sometimes 80%)
I am generally alone, and sometimes in remote locations, so, I would also like to double check, and verify my Oxygen bottles. (Preferably one that would screw right into the D.I.N. valve.)
I was leaning towards this.
OxyCheq Expedition O2 Analyzer
I would greatly appreciate your feedback..........Personal experience, and recommendations.
Edit. When. I typed "The Best."........I realized there may be models way beyond my necessity. I would like to stay in the $300 - $500.00 range. (If, possible.)
Edit. I would almost expect the reading to go from 0% to 100% (Is that not the case?)
Cheers.
How to Find the Best Scuba Oxygen Analyzer - Scuba Diving Gear
A Must Have for Nitrox Divers: Undercurrent 02/2009
Excerpt.
Analyzer Calibration
A Nitrox analyser has an oxygen sensor that generates a voltage that varies according to the percentage of oxygen present, and gives a readout on a voltmeter calibrated in percentages. An analyzer reading is affected by air pressure (weather) and the aging of the sensor cell, so before each dive, it needs to be calibrated at 20.9 percent O2 with clean air passing around it. If you calibrate using pure oxygen instead of air, the sensor readings will be three times more accurate.
Recently, I was on a liveaboard with a diver who was a gas analyst from Siemens. He merely checked his tank each time to see that he didn’t have air. He told me that the analyzer on board was so inaccurate, it was only good for telling whether you got air or something else, but nothing more. He just checked to see if it went over 21 percent but didn’t bother with a final reading. Furthermore, he said, the little oxygen analyzer that I had held so much faith in was almost totally inaccurate. I was shocked. So what was wrong with the simple equipment that was available to us?
The problem stems from gas flowing over the sensor. He pointed out that the gas had to be stationary or controlled to a known rate. By simply increasing the flow, the apparent oxygen content increased. Cracking open a tank valve “just a little’” and holding the cell over it is evidently not accurate enough for him. Temperature also makes a difference, and gas depressurizing from a tank can be very cold.
Some analyzers use the direct-feed hose to the BC, using the regulator first-stage as a flow control. It takes time to get a reading and this seems unpopular with divers impatient to get in the water. Divers will always look for the most convenient method. I have witnessed Nitrox being analyzed by holding the sensor in the mouthpiece of a regulator while the purge button was pressed.
But manufacturers have come up with designs to get a stationary sample of gas at the same ambient temperature and pressure with which the analyzer was calibrated. Some restrict the flow of gas over the cell while others attempt to capture a stationary sample. It seems that the bit of plastic tube that interfaces between the tank valve and the sensor is very important.
If your Nitrox is made by the older partial pressure blending system, you need to know your analyzer is exact, because there you may inadvertently get very high percentages of oxygen, if by mistake.
