I will be thoroughly impressed if I get a response to this thread. This topic has been found to be rather obscure as far as google searches and the like.
Here at work, we have a measuring instrument called a current-comparator bridge. The instrument allows the comparison (down to sub- part per million levels) of resistance standards.
This is achieved by comparing the differences in magnetic flux in specially-wound, identical (nearly), high-"mu" magnetic cores. The only difference between the cores is that the turns ratio on one core is adjustable via dials on the front of the instrument. In this way, the operator can run two currents through two resistors (and two cores), and adjust the dials so as to determine the precise ratio between the currents, and thereby, the resistors.
I have a book that describes the operation of these instruments in a fair amount of detail, but I am still unclear about a few things.
"Sensitivity to direct current ampere-turns or flux is achieved by modulating the magnetic core with superimposed alternating current ampere-turns, with the result that, when a direct current magnetizing force is present, even-harmonic components of the modulation are generated."
What on earth is this book excerpt talking about? Also:
"Two identical magnetic cores are normally used so that by suitable interconnection of the windings on each core the odd harmonic components tend to cancel one another and only the even harmonics remain"
Again, big question mark.
Since this is a magnetic device/magnetic amplifier of sorts, there is a modulation source that is constantly flip-flopping the orientation of the magnetic field to prevent permanent flux offset in the cores themselves. The oscillator frequency is usually just under 1,000 Hz; 700-800 Hz, typical.
My questions are as follows:
-How does a direct current comparator utilize a modulation source, highly magnetically permeable core, and two identically wound cores (and flux sensing turns), to determine the ratio of currents?
-What is meant by "even harmonic components are generated under the influence of DC magnetizing force being present"?
The circuitry that runs this instrument is equally daunting to look at. There are various sections; the oscillator, toroid diagram, peak detection/demodulator, flux amplifier, master and slave current supplies, nanovolt amplifier, turn balance, and a few other circuit boards.
If anyone can shed some light on magnetic amplifier theory, or anything in the above few paragraphs, I'd really appreciate some guidance.
I am fluent with electromagnetics and electrical engineering, but am not so fluent in specifically magnetic devices. I do understand BH curves and I do know that some are more square, while others have rounded edges.
Thanks in advance.
Here at work, we have a measuring instrument called a current-comparator bridge. The instrument allows the comparison (down to sub- part per million levels) of resistance standards.
This is achieved by comparing the differences in magnetic flux in specially-wound, identical (nearly), high-"mu" magnetic cores. The only difference between the cores is that the turns ratio on one core is adjustable via dials on the front of the instrument. In this way, the operator can run two currents through two resistors (and two cores), and adjust the dials so as to determine the precise ratio between the currents, and thereby, the resistors.
I have a book that describes the operation of these instruments in a fair amount of detail, but I am still unclear about a few things.
"Sensitivity to direct current ampere-turns or flux is achieved by modulating the magnetic core with superimposed alternating current ampere-turns, with the result that, when a direct current magnetizing force is present, even-harmonic components of the modulation are generated."
What on earth is this book excerpt talking about? Also:
"Two identical magnetic cores are normally used so that by suitable interconnection of the windings on each core the odd harmonic components tend to cancel one another and only the even harmonics remain"
Again, big question mark.
Since this is a magnetic device/magnetic amplifier of sorts, there is a modulation source that is constantly flip-flopping the orientation of the magnetic field to prevent permanent flux offset in the cores themselves. The oscillator frequency is usually just under 1,000 Hz; 700-800 Hz, typical.
My questions are as follows:
-How does a direct current comparator utilize a modulation source, highly magnetically permeable core, and two identically wound cores (and flux sensing turns), to determine the ratio of currents?
-What is meant by "even harmonic components are generated under the influence of DC magnetizing force being present"?
The circuitry that runs this instrument is equally daunting to look at. There are various sections; the oscillator, toroid diagram, peak detection/demodulator, flux amplifier, master and slave current supplies, nanovolt amplifier, turn balance, and a few other circuit boards.
If anyone can shed some light on magnetic amplifier theory, or anything in the above few paragraphs, I'd really appreciate some guidance.
I am fluent with electromagnetics and electrical engineering, but am not so fluent in specifically magnetic devices. I do understand BH curves and I do know that some are more square, while others have rounded edges.
Thanks in advance.