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deanc · 12th November 2007, 12:24

Quote: (Originally Posted by denismc66)

I have noticed something similar on my unit once or twice, i have the temperature set to metric and when i enter this menu the loop temperature can appear as high as 200 degrees. I am only new to the unit so i will watch this in the future. I have apecs 2.5

Thats interesting in version 2.5, a common bug to 2.01 may exist. I wonder if ISC could ever reprogram the computer, say it was more serious, like a fault in random PO2 readings, Steve?

Quote: (Originally Posted by Gadget)

the reason you see the fault is because of the cable length between the hanset and the head. the sensors are annologue and occasionally they read a bit of spurious data. scroll around to the screen again and it will be fine.

Dont agree on the cable length having anything to do with it. I do scroll around 16 times and that hardly affects the cable length, can it. Its a software issue, like you said sporadic *data*.

You may be right on a faulty thermocouple/resistor, but this sequence seems too repeatable for the wiring to be faulty.

Of course its analogue, there would be an analogue-to-digital converter ADC to convert the resistance/voltage/current to binary coded decimal BCD or alike for the display, with signal conditioning or a lookup table or math function to condition the signal into an integer celcius/farhenheit number, and add a false decimal place. This is the likely bug, in the conversion math routine.

I wouldn't know the circuit diagram but guessing its a 2-wire RTD then the cable resistance is negligible compared to say a platinum PT-100 ohm resistance at 0 degrees, and 0.385 ohm/degree. Open circuit goes 0 ohms. 3-4-wire RTDs can go kilometres.

If it was a thermocouple then its a junction which only forms at two dissimilar metals, type K Cr-Al. The cable (twin-core) can be hundreds of metres long, i.e. like in process control industry with no real effect. Open circuit goes 0 uV

Really the cable is just so negligible, unless the insulation has worn through or the junction is loose (i.e. a broken weld/resistor). They work or they dont.

The analogue-to-digital may even occur in the head/computer, not the handset, maybe there's serial communication between the handset and computer?

12th November 2007, 12:24	#5 (permalink)
deanc New Member Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Dec 2006 Location: Perth, WA Posts: 52	Re: Loop temperature code Quote: (Originally Posted by denismc66) I have noticed something similar on my unit once or twice, i have the temperature set to metric and when i enter this menu the loop temperature can appear as high as 200 degrees. I am only new to the unit so i will watch this in the future. I have apecs 2.5 Thats interesting in version 2.5, a common bug to 2.01 may exist. I wonder if ISC could ever reprogram the computer, say it was more serious, like a fault in random PO2 readings, Steve? Quote: (Originally Posted by Gadget) the reason you see the fault is because of the cable length between the hanset and the head. the sensors are annologue and occasionally they read a bit of spurious data. scroll around to the screen again and it will be fine. Dont agree on the cable length having anything to do with it. I do scroll around 16 times and that hardly affects the cable length, can it. Its a software issue, like you said sporadic data. You may be right on a faulty thermocouple/resistor, but this sequence seems too repeatable for the wiring to be faulty. Of course its analogue, there would be an analogue-to-digital converter ADC to convert the resistance/voltage/current to binary coded decimal BCD or alike for the display, with signal conditioning or a lookup table or math function to condition the signal into an integer celcius/farhenheit number, and add a false decimal place. This is the likely bug, in the conversion math routine. I wouldn't know the circuit diagram but guessing its a 2-wire RTD then the cable resistance is negligible compared to say a platinum PT-100 ohm resistance at 0 degrees, and 0.385 ohm/degree. Open circuit goes 0 ohms. 3-4-wire RTDs can go kilometres. If it was a thermocouple then its a junction which only forms at two dissimilar metals, type K Cr-Al. The cable (twin-core) can be hundreds of metres long, i.e. like in process control industry with no real effect. Open circuit goes 0 uV Really the cable is just so negligible, unless the insulation has worn through or the junction is loose (i.e. a broken weld/resistor). They work or they dont. The analogue-to-digital may even occur in the head/computer, not the handset, maybe there's serial communication between the handset and computer? __________________ You dont know what you dont know.
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