Accuracy of data presented in mV or PO2

Meng_Tze · 4th April 2008, 14:19

Quote: (Originally Posted by David Pye)

That's not particularly helpful, is it? Admittedly I was a bit unclear but I think we're using the word accuracy differently.

When I say I don't care about accuracy, I mean that I don't care about say +/- 0.1bar error in PPO2 for example. I do care if the data displayed on the screen is from 10 minutes ago, or bears absolutely no relation to the voltage output from the cells. That (to my mind) isn't accuracy in the terms of error margin.

If that makes sense.

David

That explains it yes.

bgpartri · 4th April 2008, 15:40

Quote: (Originally Posted by silent running)

But would the surface mv values be affected by a bad cal and not quite as accurate as using a muti-meter directly on the sensors if you have reason to believe the sensor is faulty?-Andy

No. The mV muliplication factor is determined at hardware design time. It is a calculation of gain and refererence voltage. It the same on every Pursuit shipped.

Would the Pursuit be as good a measuring device as a Fluke multimeter. Absolutely not.

On the other hand, the mV in air doesn't tell me much except that there is a cell connected. Just because a cell is 9 mV in air doesn't mean that it's not current limited. The check I am most interested in is comparing the mV in air to the mV in O2, and a multimeter isn't much use for that.

Of course the only test that really matters is getting the PPO2 up above 1.3 underwater.

Bruce

4th April 2008, 14:19	#21 (permalink)
Meng_Tze 246 Bubbleless Cove Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Jan 2007 Location: FL, USA Posts: 111	Re: Accuracy of data presented in mV or PO2 Quote: (Originally Posted by David Pye) That's not particularly helpful, is it? Admittedly I was a bit unclear but I think we're using the word accuracy differently. When I say I don't care about accuracy, I mean that I don't care about say +/- 0.1bar error in PPO2 for example. I do care if the data displayed on the screen is from 10 minutes ago, or bears absolutely no relation to the voltage output from the cells. That (to my mind) isn't accuracy in the terms of error margin. If that makes sense. David That explains it yes. __________________ Homo Bonae Voluntatis
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4th April 2008, 15:40	#22 (permalink)
bgpartri Rebreather Zealot Current Rebreather/s: Megalodon Other Rebreather/s: Inspiration Classic Sport Kiss Classic Kiss Titan Join Date: Apr 2005 Location: Vancouver, Canada Posts: 412	Re: Accuracy of data presented in mV or PO2 Quote: (Originally Posted by silent running) But would the surface mv values be affected by a bad cal and not quite as accurate as using a muti-meter directly on the sensors if you have reason to believe the sensor is faulty?-Andy No. The mV muliplication factor is determined at hardware design time. It is a calculation of gain and refererence voltage. It the same on every Pursuit shipped. Would the Pursuit be as good a measuring device as a Fluke multimeter. Absolutely not. On the other hand, the mV in air doesn't tell me much except that there is a cell connected. Just because a cell is 9 mV in air doesn't mean that it's not current limited. The check I am most interested in is comparing the mV in air to the mV in O2, and a multimeter isn't much use for that. Of course the only test that really matters is getting the PPO2 up above 1.3 underwater. Bruce __________________ http://www.shearwaterresearch.com Good judgment comes from experience. Experience comes from bad judgment.
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