The HackingPhysics Journal Vol.1, no 3 (July 2020): Low-Cost Precision Voltage and Temperature Measurements by Bogatin Eric

The HackingPhysics Journal Vol.1, no 3 (July 2020): Low-Cost Precision Voltage and Temperature Measurements by Bogatin Eric

Author:Bogatin, Eric [Bogatin, Eric]
Language: eng
Format: epub
Publisher: Addie Rose Press
Published: 2020-05-13T00:00:00+00:00


Figure 3.20 Measured voltage across the lower resistor in the voltage divider when I touched it. The voltage dropped by 0.2 mV out of 1246 mV, or 0.016%.

We measured a change of 160 ppm. If the resistor’s coefficient is the same as pure carbon, this would have been a fraction of a degree change in temperature.

3.9

Experiment: voltage across a 2.2 V Zener diode with 2 mA forward current

In this example, a very old Zener diode was used, in reverse bias mode, that was rated at 2.16 V. A 1k resistor connected to the 5 V supply. This means the reverse current was about 3 mA.

The reverse voltage on the Zener fluctuated about 600 uV out of about 2.2 V, over a period of about 15 minutes. This is still very stable, to within 0.03%, but easily measured with this system. Figure 3.21 shows the measured voltage on the Zener diode in this experiment.



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