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RE: RE measuring inductance
Subject: RE: RE measuring inductance
Date: Mon, 5 May 97 15:36:12 UT
From: "William Noble" <William_B_Noble-at-msn-dot-com>
To: "Tesla List" <tesla-at-pupman-dot-com>
Your comment about 2 volts is suspicious - LED's are diodes which emit
when
forward biased - depending on the LED, there will be one or more
"standard"
diode drops in the forward direction - most red LEDs are a single diode,
so
0.7 volts will cause them to turn on. I have some green LEDs here that
take
1.4 volts (e.g. they have 2 diodes in series). You can easily determine
what
you have by putting some current through the LED (with a suitable
dropping
resistor) and then measuring the voltage across the LED.
I would recommend using low power LEDs not the new super bright ones for
your
kind of work - you could use an OP amp circuit and a meter or just a DVM
too,
of course, but the LED is pretty simple.
[Bill] snip
The LED requires a bit more than 2 volts to become forward biased,
and only then will current *begin* to flow through it. I have one RF
Generator that only puts out a measley 2 volts. And it has a
disgustingly high output impedance. The LED will give decent visible
indication beginning at about 1/10th of a milliamp. The series
resonant circuit has maximum current flow through it at resonance,
but the LED will only light if the VOLTAGE across the LED exceeds the
forward bias point.
[Bill] snip