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10.
Measuring Resistance
When measuring resistance both the external load resistor as well as the 1 ohm sense resistor
built into the circuit board must be taken into consideration.
Example 1:
The illustration below shows a 10 ohm load resistor placed across one set of the OUTPUT
terminals. The total resistance is really 11 ohms (10 ohm load resistance + 1 ohm sense
resistance). While the fuel cell is shown as the power source, a battery, solar panel or wind
turbine can also be substituted.
USB
Connector
The equivalent circuit is shown below:
+5V
Microprocessor
GND
1 ohm
sense
resistor
= 11 ohms total
10 ohm
Load
resistor
16
Voltage
LED
Current
LED
INPUT
1 ohm
sense
resistor
OUTPUT
O
H
ME
A
10 ohm
Load
resistor
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