Quote: (Originally Posted by whoizrob)
I may be over thinking this but has anyone fully potted a handset?
I am thinking about possible soultions for DIY PP02 metering on my Rebreather design but most DIY meter designs require a housing and can be bulky when you include a battery compartment. I wanted to place the battery and trim pot along with the sensors in a compartment in my scrubber and just pour potting resin all over the LCD screen and board (using a mould of course).
Is there any reason not to do this? I understand some resins can be reasonably exothermic when curing but that can be avoided depending on which formulation you use.
Thanks,
Rob
If you're talking about just PO2 metering, like the Mark Munroe (PPO2.com) units, it just isn't practicle.
Those particular Datel DPMs can't reference the analog signal to supply voltage negative, so you'd need 2 power (battery) wires, cell wires depending on number of cells, and then there's the trim pot wire issue! .... Another bunch of wires, all of which are low level and wanting to pick up noise and cause error.
You'd be better to build a op-amp circuit that converts the cell millivolts to a higher level, using a 2V range DPM and then 1.000 PO2 would be 1.000V. You could use the 5V supply DPMs, (same power supply for the op amp and display) as you can reference the analog voltage to power negative. (saves a conductor in the cable) You could calibrate the DPM once and then seal it. The op amp board would reside with the battery and the cal pots would finely adjust the gain of the op amp circuit.
The only other way would be more complex and require a microcontroller so you could use software calibration. That would still require "buttons", but they can be magnetically seperate from the potted components.
The HSE PPO2 meter (uses the same case as the HS Explorer) is that type of implimentation readily available.
Good luck,
Darlene