i would try dropping a piece of polly pipe down the well leaving both ends open, drop a piece of resistance wire down the center of the polly.
the polly will insulate the resistance wire from anything it might touch on the way down.
Then (presuming that you arent getting distilled water out of...
you could use something like an lm334, current regulator, i dont know what its upper voltage rating is but i doubt it would to 2kv, or you could use a voltage regulator of the biggest value you can lay your hands on, just connect the gnd pin to the output via a resistor, your load then comes off...
can you state:
min and max supply voltages and curents
what relay you intend to use and the specs for that relay
can you get a different supply? as aposed to changing an existing one.
i would splice the output of your headphone jack into a 1:1 audio transformer to overcome any impedance problems and then just turn down the volume on the phone toget a better quality recording
could just use the clasic astable curcuit...couple of transistors couple of resistors couple of capacitors (the product of the resistor and capacitor values gives an approx time constant it cant be dead on because of the variance in transistor trigger voltages) when you want to stop the flashing...
you could just use a paralell to serial converter such as what you can get from tandy few dollars and you can use the 5v power rail in your computer for the supply, reduces curcuitry, you say serial input in the question so i presume you only want to go from the computer to your m/c if you want...
if you are talking about using the display off a set of scales to use as you data in then you will have to trace it back to before it gets multiplexed then take that load of data (most likley BCD) and put it through something like a pic chip to do your conversions then output this if possible in...
i think your problem is that you want to test the cap before it blows up but after you have put power to it, this is not a good idea as after puting a reversed potential accross it you have already done some damage, so it is probably best that you let it blow up then go around with a schematic...