In this thread I will be going over a few methods to find the parameters of a transformer using the Transformer Test Jig and with the software tools I presented in this forum here, http://www.esldiy.com/esldiy/forum/index.php?topic=177.msg325#msg325
I have shown some examples in that thread and here we will be taking a closer look at how to find the parameters that we are looking for.
As well as how they apply when transformers are used as step-up devices in a ESL system.
These same procedures are also used if the transformer is to be used as a step-down device as well for such systems using ribbon drivers.
But this is basically to help explain the mysteries of the almighty step-up transformer for ESL use.
Among the software tools I described in the Transformer Test Jig thread, It is advisable that you have a good standalone signal generator and oscilloscope should you have to encounter any frequency's of about 40Khz or higher.
Also a good frequency counter is almost essentially a must as well for some of these tests to be accurate.
If you have a good sound card that does 24 bit or 16 bit that does do 192Khz sample rate then you may be able to get by quite nicely just using the software tools I presented earlier.
I will be using both in this tutorial as my sound card does run at 192Khz but only reliably in 16bit mode in Visual analyzer and all of the required test functions are built right into the program it self.
I am not going to go over exactly how to operate each of the programs in complete detail and it is up to you to become familiar with them.
But, I will gladly try to answer any questions that you may have to the best of my ability should you have any issues as I did not write these programs.
They are very easy to use and there are plenty of troubleshooting resources on the web where they came from.
What I have done was taken the time to fully test them to make sure that they work for what we are trying to do here.
Our main goal is to is to find out what kind of load our ESL system is presenting to the amplifier.
This is called an Impedance Curve and by using the methods I am about to describe you can plot your curve manually and I will also show how to do this automatically using a few different programs.
Then, I will take our newly found data and apply it to a spice model in a simulation program such as LTspice or Cicuitmaker to check our results.
I will be using Circuitmaker2000 of course as I am most familiar with it and it is extremely easy to use.
This program can still be found on the web if you search hard enough but LTspice is the latest greatest program for electronic circuit simulations and it is free.
LTSpice can be found here,http://www.linear.com/designtools/software/
One last note If you are using a typical digital volt/ohm meter chances are that any voltage measurements that you do at frequency's above about 50hz to 120hz can/will be inaccurate.
I have this problem and it has plagued me to no end, and, is why I have had to revert to using software tools and a good sound card for some of the measurements.
The sound card method is very accurate but it is only good for A.C. voltage measurements and luckily Transformers are A.C. devices.
This won't be an issue if you happen to have a good Meter designed to measure voltages over a very wide frequency range.
Being able measure resistances accurately is a must as well as my meter is off by as much as 10% to 15% or so when switching between ranges and this is very sad.
I sometimes have to use a regulated voltage source such as a LM7805 and measure the current flowing through the resistor and use ohms law to find an exact resistance for my reference resistors.
The ma. current measuring function seems to be fairly accurate on my meter but I still don't have a 100% refference to be completely sure of its errors.
I do use some bridge measurement techniques to assure the accuracy by comparison and good ole' long hand ohms law.
With a calculator of course!!! He,he,he
I can also use VA to do this as well.
I mentioned how I did this in the TTJ thread to measure my home made 1 ohm power resister out of some twisted pair cable to find it is actual value of resistance of about 1.134 ohms or so.
This is the very first meter I have ever owned that I have had this problem with.
It is a Cen-Tec P37772 so if you should ever see this meter and think it is a good deal don't waste your money on it even if it is on sale.
When I got it I had no meter and it has gotten me by with my Variable HV supply project.
As it was during that time that I had discovered its great inaccuracies.
Because of this it has made everything much much more difficult than it really is.
It was however the main reason I had to build the transformer test jig in the first place as I had mentioned in that thread.
More to come soon !!!
Are you ready?