On 10/18/21 6:04 PM, Roger Need via groups.io wrote:
On Mon, Oct 18, 2021 at 11:59 AM, Gary O'Neil wrote:
Some may find this does-it-all calculator useful also. It is my go to site for
all things toroid.
¡. and even obvious and easy to remember and get to.
Just type the following in the address bar of your browser and hit enter.
Toroids.info
Gary,
There are several calculators online like the one at toroids.info that have a common error. They assume that the initial permeability is the same with frequency. This is not true with ferrite toroids. So if you wanted a ferrite toroid for operation at 3.6 MHz. and you calculated the number of turns required using this calculator you would find the inductance to be lower than expected at 3.6 MHz.
Here is an example. I wound a FT50-43 toroid with 4 turns of 28 AWG wire. Toroids.info gives and inductance of 7.04 uH (see attached graphic). Using a one port VNA (Rig Expert AA-55 Zoom) I measured 4 uh - a considerable difference. A better toroid calculator is needed.
Owen Duffy has covered ferrites extensively on his blog and publishes calculators which take "complex permeability" into account. Here is a link:
The first step using his calculators is to get the manufacturers data sheet and get Al and the initial permeability ?i for the toroid size and mix. For a FT50-43 it is 440 and 800 respectively. The next step is to calculate the complex permeability ?¡¯ and ?¡± at the frequency of operation. Duffy provides a calculator to determine these values. At 3.6 Mhz. for Mix 43 we get ?¡¯ = 470.2 and ?¡±. If we enter this into his inductance calculator we get 4.14 uH which is pretty close to the experimental results. Screenshots of the calculated inductance and measured data are attached.
That's the cool thing about Miguel Vaca's program - it takes the data from Fair-rite which gives mu' and mu'' vs frequency and does the calculations.
