EMRFD Message Archive 4966
Message Date From Subject 4966 2010-08-31 09:08:55 WA0ITP Toroid Windings and Inductance values For a current project I'd like to wind inductors that are as
close as I can get them to the required values. Is it
worthwhile to adjust the windings, using the AADE LC Meter,
to hit the target value?
I think the meter uses about 1kc to make its measurements
and it seems that to be accurate the measurements need to
be made at the frequency of use. Perhaps the signal
generator/series resistor/impedance calculation setup is
TIA for any opinions.
I love this radio stuff !
72, 73 Terry, WAØITP
4967 2010-08-31 09:48:18 Dan Rae Re: Toroid Windings and Inductance values 4968 2010-08-31 10:48:31 Garey Barrell Re: Toroid Windings and Inductance values Terry -
Maybe, maybe not!
The AADE measures at ~100 kHz, I think. Very low frequency anyway. All
you have to do is look at the permeability curves for the toroids you
are using to see how they vary with frequency. Some vary MUCH more than
others. You'll notice that all the coils that Neil did calibration
comparisons on are all air wound.
Air wound coils will correspond pretty much regardless of measurement
frequency. Coils wound on frequency sensitive toroids MAY not correspond.
Simple enough to measure a sample coil both with the AADE and with the
generator/capacitor/scope method and compare the results.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B, C-Line& TR-4/C Service Supplement CDs
> For a current project I'd like to wind inductors that are as
> close as I can get them to the required values. Is it
> worthwhile to adjust the windings, using the AADE LC Meter,
> to hit the target value?
> I think the meter uses about 1kc to make its measurements
> and it seems that to be accurate the measurements need to
> be made at the frequency of use. Perhaps the signal
> generator/series resistor/impedance calculation setup is
4969 2010-08-31 10:55:16 Nick Kennedy Re: Toroid Windings and Inductance values I think with powdered iron toroids, the inductance reading is OK at the low
frequency, but for ferrites, it might be a lot different at HF than at the
measurement frequency. Fortunately, it's usually circuits with powdered
iron toroids where the exact value of inductance is important (tuned
circuits, filters). My AADE meter is one of my most used instruments.
Still, I've been thinking of taking a crack at this meter by N5ESE -
>[Non-text portions of this message have been removed]
4970 2010-08-31 11:08:27 Ashhar Farhan Re: Toroid Windings and Inductance values there is no substitute really for an in-situ measurements at the frequency
i would gather that most probably you are going to use this either in a
filter or in an oscillator.
in both cases, the final tweaking is well worth doing with a signal
generator (for a filter) or a frequency counter (for an oscillator).
however, the final tweak is always by the ear unless you can have access to
something like the VNA or a spectrum analyzer.
4971 2010-08-31 11:31:53 w4zcb Re: Toroid Windings and Inductance values >I think with powdered iron toroids, the inductance reading is OK atDo NOT have a AADE, but do have a W7AAZ (K6OLG) LC meter that works
> frequency, but for ferrites, it might be a lot different at HF than
> at the
> measurement frequency. Fortunately, it's usually circuits with
> iron toroids where the exact value of inductance is important (tuned
> circuits, filters). My AADE meter is one of my most used
the same way but measures the inductor at around a MHz. Quite often, a
toroidal powdered iron inductor wound for a filter at 28 MHz will be
about 1 turn too many which has to be removed for proper inductance as
measured by either my N2PK VNA or the end filter results.
A toroid at 1 MHz isn't the same thing as one at 28 MHz, and a wider
spread between measured frequency and application frequency is NOT
on the side of the angels.
4973 2010-08-31 14:11:59 Andy Re: Toroid Windings and Inductance values The other thing that affects the inductance vs. frequency, is
inter-winding capacitance. As it approaches self resonance, the
apparent inductance of the coil starts going up, approaching infinite
Henries at resonance. So watch for that too if you might be using it
somewhat near its resonance.
4974 2010-08-31 14:42:33 w7zoi Re: Toroid Windings and Inductance values Hi Terry and group,
No, the AADE operates at a higher frequency, well above 1 kHz. Audio frequency measurements are common with some traditional instruments though.
I recently wanted to use my AADE meter to evaluate a piece of transmission line to determine Z0. This was done by measuring a short length of the line. The C with the far end open and the L with the far end shorted gave me C and L per unit length for the cable. The square root of the ratio then provided Z0. But there is a flaw in the method: The measurement should be done on a length of cable that was short compared with a quarter wavelength. To determine this, I needed to measure physical length and the frequency where L and C were determined. A simple ratio works if the cable is really short. If not, one can infer details with more detailed transmission line calculations. In either case, one must know frequency.
Hence, I did a modification to my AADE LC Meter. A series 120K R and .01 uF capacitor were attached between the output of the LM311 oscillator and a tip jack that was added to the side of the plastic box. A floating solder lug was also placed on a bolt in the plastic. The lug was attached to an internal ground with a 100K resistor. A frequency counter could then be attached to this port. I usually did this with an oscilloscope probe. Even with the "floating ground", there was a slight frequency shift when the counter was attached. The AADE circuit reverts to the original topology when nothing is attached to the added port, with the exception of a couple of pF of stray. I measure F=0.784 MHz when the AADE meter is in the L position and the terminals are shorted for calibration. Perhaps F gets down to very low values with large valued capacitors, but it is otherwise in the almost 1 MHz area.
It is certainly great to have a battery operated instrument with digital readout for L and C measurements. I really love my AADE meter. A similar uP based instrument designed by W7AAZ was mentioned in a related post by W4ZCB. Others pointed out that there were other ways to do the measurement. But if you have a frequency counter, but don't have one of the commercial boxes, the measurement can still be done with bench sweepings parts. Recall that this was
4976 2010-08-31 17:55:48 jmsheph Re: Toroid Windings and Inductance values If you have acess to one, you should perhaps use a vector network analyzer at the frequency, or range of frequencies, to which you plan to subject the toroid. Then adjust the windings acordingly.
There is an incredible kit that you can buy to build one of these, that operates off the USB port of a computer and is based
4979 2010-08-31 19:59:02 WA0ITP Toroid Windings and Inductance values Thanks to all who repsonded to my post, I appreciate it.
Looks like the LC meter is adequate for my needs, filter
I love this radio stuff !
72, 73 Terry, WAØITP