Science Buddies: "Ask an Expert"

I am doing the second part of my experiment "how long does it take to fry a diode?"
I keep the same setup except outside of the oven.
And when I am soldering the diode lead the voltage reading flies all over the place.
For example 5 seconds = 8.31 volts, 15 seconds = 7.98 volts, 25 seconds = 7.56 volts, 35 seconds = 7.33 volts, 45 seconds = 7.67 volts, and at 55 seconds = 8.05 volts.
And after a while , as shown in my example, the voltage reading goes back up.
Is this ok and if so am I in the right voltage reading range.

tylerkaz - This experiment uses a very low level of current, approximately 9 microamperes for the test. The data suggests that the Forward voltage drop, over a wide temperature range of 25-75 degrees C, to be between 380 and 260 millivolts. The curves of the three diodes shown shows the one device, NTE-125 to be way out of range that I would expect for a 1 amp diode, similar to a 1N400x series device. It should read similar to the other two devices. In any case, your readings of voltages in the range of 7-8 volts seems very incorrect, unless the diode has in fact been compromised and is now destroyed. You should see voltages in the several hundred millivolt range, even with the soldering iron in contact with the leads. A possible error could also occur if your soldering iron is not grounded to the device. At these very low currents, leakage currents could cause inconsistent readings. Are you measuring forward voltage drop across the diode, not the battery? What if you use a 10K or 100K ohm resistor to provide your 'constant current' loop. That would increase the forward current through the diode and make your reading more typical.

Rick Marz