TPS question

Just checked my TPS and the inital voltage reading was 4.70 while in the "on" ignition position(engine off), is this too low? I tested the TPS by checking this voltage(terminal a&d), then adjusted my voltage between b&d so it was 82% of this initial reading. The adjustment was only out by .02 volts, but it's spot on now.
I'm just wondering if the initial reading of 4.70v is too low to properly operate? Everything that I have read said it should be "close to 5.0v" How close is close enough? Is there any way I can adjust this so it is closer to 5.0v or is it a non adjustable figure?
thanks!

That is not a problem. I have found that when you see the voltage too low, check the ground between the head and the firewall. Actually all readings are scaled to the power supply level within the computer anyway so you will be fine. That power supply voltage is actually derrived within the computer and distributed to the sensors.

How and where do you adjust the voltage once you decide it is too low or too high?

The ground connections looked okay--not rotted off in any way, just kinda rusty. Should i try cleaning the two connections between firewall and head or is that getting excessive? Just how good does the ground have to be?