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Circuit 46: Meters for 1.5 V Zener diodes and higher
Setup information
Install the two transistors and the three resistors as shown in Fig. 2.46. The seven jumper wires come next.
Last but not least connect the moving-coil instrument. Check the placement on the board again and only
then connect the battery.
Experiment
The Zener diode meter shows the Zener voltage of a properly functioning Zener diode on the moving-coil
meter.
Please note: Zener diodes are connected in the reverse direction!
Look for Zener diodes in your crafting box. If you find one within the voltage range of 1.5V to 4.3V, you could
test them now. The Zener diode is faulty, if it shows either no or full-scale deflection when operated reverse-
biased as well as forward-biased.
If you cannot find a proper Zener diode, you could get around with the following: Get a green LED and place
this pseudo Zener diode into the meter in forward-bias. The threshold voltage will be displayed.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.46.
Components required:
2 x 2N3904 transistors,
1 x 220 Ω resistor,
1 x 2.2 kΩ resistor,
1 x 4.7 kΩ resistor,
1 x moving-coil instrument,
1 x breadboard, 1 x 9V bat-
tery with clip connector
Fig. 2.46: Meters for 1.5 V Zener
diodes and higher
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