calibration problems

silkyshark

silkyshark

Member
hi all , any ideas as to why , when i calibrate in o2 that the shearwater reads .98 which is normal , but the shearwater hud once calibrated in the same gas content, blinks two reds?
cheers
gordy,,
 
the calibration gas is o2 , both the computer and hud are calibrated in o2 , after which the computer displays .98 and the hud flashes red twice which is an incorrect reading for pure o2 ,,
cheers
 
I am not sure of the problem with the HUD. 2 red blinks would indicate a po2 of .8 if it is a SW HUD.

there is a place in the "system setup" on the shearwater computers where you can set the fo2 of calibration gas. IIRC it can be anywhere from .98 - 1.00

this can make a difference in the calibrated readings.

Void all my ramblings, I missed the part where you said .98 on the SW was normal. As for the HUD, I would suspect splitter or connection problems
 
On the HUD. Are all three cells showing .8? If so, I would suspect the common ground to be the fault.
 
If the calibration gas setting on the SW is set to 0.98 then it will show 0.98.
I suggest trying another calibration O2 flushing to check again.

Cheers!
 
all 3 cells reading .8 in pure o2 , battery is good , and i have flushed o2 through the unit 4 times ,
i suspect a fault here somewhere but not sure where to start from ,
ideas on a postcard
 
Did you definetly calibrate the HUD as the cells were reading as close to 0.98 as possible, or could you have calibrated the HUD before they reached 0.98, or well after the solenoid stopped firing?

Silly question, but sometimes...
 
Wait...

So I'm reading that you calibrate against a gas (which to my understanding just tells the HUD brain "You're now looking at 100%, sort yourself out"), then run it against the same gas and it's telling you 80%.

Correct?

If so, bizarre. Worth maybe having a look at the raw mV readings on the cells if possible, although that amount of rounding error would indicate the kind of very dead cell that a setpoint controller could/should be complaining about...
 
Given this is a rEvo thread can I check you actually have a shearwater HUD rather than a dream HUD?

If so does the shearwater HUD have pressure compensation to allow for calibration at elevation?
 
MeRodent said:
Given this is a rEvo thread can I check you actually have a shearwater HUD rather than a dream HUD?

If so does the shearwater HUD have pressure compensation to allow for calibration at elevation?
Click to expand...

The original shearwater HUD does not. The newer one supposedly can be plugged in to a petrel and use its pressure sensor. The NERD display is a petrel and has a pressure sensor.


Sent from my iPhone using Tapatalk - now Free
 
yes its a shearwater hud and predator comp ,,
something is amiss for sure , i have checked and rechecked , the gas is pure o2 , i have flooded the loop 4 times with pure o2 then calibrated both the hud and computer , both systems pass calibration as per manual, then as soon as the hud calibrates it begins flashing twice red which means below .9 ie .8 something or other .. while the comp remains at .98 ,,
then all through the dive the hud reads below the comp by at least one point ,,
strange brew indeed !!
silkyshark ,,,
 
silkyshark said:
yes its a shearwater hud and predator comp ,,
something is amiss for sure , i have checked and rechecked , the gas is pure o2 , i have flooded the loop 4 times with pure o2 then calibrated both the hud and computer , both systems pass calibration as per manual, then as soon as the hud calibrates it begins flashing twice red which means below .9 ie .8 something or other .. while the comp remains at .98 ,,
then all through the dive the hud reads below the comp by at least one point ,,
strange brew indeed !!
silkyshark ,,,
Click to expand...

Who wired the Shearwater HUD into your rEvo for you?
 
the comp and hud run on two separate wiring paths which converge at the cells via a set of splitters , since all the leds on the hud are reading the same it stands that the splitters are fine , since it would take all three to fail at the same time , the condition of the splitters is good ,
silkyshark
 
silkyshark said:
the comp and hud run on two separate wiring paths which converge at the cells via a set of splitters , since all the leds on the hud are reading the same it stands that the splitters are fine , since it would take all three to fail at the same time , the condition of the splitters is good ,
silkyshark
Click to expand...

Have you tried calibrating the HUD by itself, eliminating the splitters?
 
The only common for all three LED's on the SW HUD is the ground wire. It is possible that there is a connection issue where it splits into 3 separate wires to run to the cells.

If that is not the problem, i would guess that the HUD needs to go back to SW for a check, as it might be in the circuit board.
 
silkyshark said:
the comp and hud run on two separate wiring paths which converge at the cells via a set of splitters , since all the leds on the hud are reading the same it stands that the splitters are fine , since it would take all three to fail at the same time , the condition of the splitters is good ,
silkyshark
Click to expand...

Are you using the splitter wires provided by rEvo?
Those splitters are used for the Predator and the Dream and has a 10K resistor for the Predator side which reduce about 10% of cell millivolts. Could you have wired that to your HUD?

Cheers!
 
Even if he did, it would calibrate against 10% less too.

If you're calibrating against a gas and re-present that same gas it should show the same output to the HUD electronics.

So either the HUD electronics are being weird (ie return to SW) or something is different between when you calibrate and when you O2 flush the loop.

If, as soon as you triple-tap the HUD stud and calibrate, it locks red for five seconds and then immediately starts displaying two red flashes and you've done nothing to change the gas presented to the sensors? Then you've gone immediately from telling it "this is 100%" to it telling you "Nah, it's not": that's a problem in the HUD.

Simple things first though, can you swap a spare sensor into the rig and see if it continues to misbehave like this? And swap a spare SAFT battery into the HUD? Just to eliminate the dumb stuff before you go through the pain of shipping off the HUD...
 
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