I was doing an experiment to plot the IV characteristics of a diode. I connected a resistor, diode and milli ammeter in series. I connected a voltmeter across the diode. I measured the diode voltage and diode current. When i changed the resistor, I got a different set of diode voltage readings for the corresponding diode current. Why are the readings different? Before I changed the resistor, i waited for 15 mins to allow the diode to cool back to normal temperature. The ammeter resistance is 0 and voltmeter resistance is infinite.