How do I measure the efficiency of a Joule Thief?

[Dark Alchemist]

I'm new to all this.

So, if you would kindly explain the "1 ohm" method and give me an idea of what the setup would look like for the two meters, I would be very grateful.

Thank you for your patience with a neewbie.

Carlos

The one ohm method is in that video I linked and he shows you on his scope but you could use a DMM as well but that is for LEDs which I can't even attach a probe to in my Multisim simulator when running DC Sweep Analysis.

[carlprad]

is it as simple as attaching an ammeter at the input and an ammeter at the output and measuring the difference?

[Dark Alchemist]

is it as simple as attaching an ammeter at the input and an ammeter at the output and measuring the difference?

For an LED no but for a battery that has a resistance I am not sure.  What I am thinking is that if you simply hooked up a meter at the outgoing battery it would be skewed due to that battery having a voltage.

Maybe adding a fast switching diode before the battery and measuring the opposite side that is away from the battery?  At least that would prevent the battery from injecting its voltage/current into the meter since the diode would stop that.

[MileHigh]

A real Joule Thief operates off a single 1.5-volt battery and has one or more LEDs as the load.  Because of it's somewhat unusual operating characteristics and the fact that LEDs complicate the output power measurement because they are what is called non-linear electrical devices it's actually much more complicated and difficult than you think.

The real way to do it would be with a digital storage oscilloscope.  Preferably you would have one with a built-in math function.  You have to measure the instantaneous voltage and current output by the battery, as well as measuring the instantaneous voltage and current across the LED.

It just happens to be a circuit where multimeters and a basic scope will not cut it and you can't really make the power measurement unless you have the right equipment and you really know what you are doing.

MileHigh

[Dark Alchemist]

A real Joule Thief operates off a single 1.5-volt battery and has one or more LEDs as the load.  Because of it's somewhat unusual operating characteristics and the fact that LEDs complicate the output power measurement because they are what is called non-linear electrical devices it's actually much more complicated and difficult than you think.

The real way to do it would be with a digital storage oscilloscope.  Preferably you would have one with a built-in math function.  You have to measure the instantaneous voltage and current output by the battery, as well as measuring the instantaneous voltage and current across the LED.

It just happens to be a circuit where multimeters and a basic scope will not cut it and you can't really make the power measurement unless you have the right equipment and you really know what you are doing.

MileHigh

Does that go for his battery to JT to battery setup as well?