(a) Control Settings
(b) Result
Figure 15: 2N7000 N-Channel MOSFET
•
Indicator LEDs. From left to right these are:
Green
USB Power ON.
Red
48V Power ON
Flashing Red
Communications traffic.
Amber
Status. Illuminates when a measurement is in progress. Flashes to indicate over-temperature con-
dition.
The hardware microprocessor accepts commands from the host to set the various D/A converters and acquire
various measurements. It then sends the acquired data to the host, for display and storage.
Commands are in the form of ASCII strings, so it is quite straightforward for some other software to control
the CTR-201 hardware.
Example: Diode Measurement
A diode is connected with the anode connected to the
Base
terminal and the cathode to
Collector
terminal.
The base current source forces current through the diode. The ammeter in the Collector circuit measures this
current
4
. The voltage across the diode is equal to the base voltage reading minus the collector voltage reading.
Example: PNP Transistor Measurement
The PNP transistor is connected to the like-named terminals on the curve tracer. The emitter and collector voltage
sources are raised to some positive voltage. The base current generator is configured to sink the first value of base
current. The collector voltage is then swept downward so that the emitter is more positive than the collector and the
4
The diode current is known from the current source setting, which is quite accurate, so the collector current measurement is redundant.
However, the collector current measurement is very precise, with high resolution, so we use that.
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