I have some handheld LCR meters and a couple of bench models. For what I want to show in this thread, I'll be using the bench models. They are the Hioki IM3570 and the Keysight E4980A. The Hioki covers the range 4 Hz to 5 MHz, with a maximum stimulus voltage of 5 volts. The Keysight covers 20 Hz to 2 MHz, with a maximum stimulus voltage of 20 volts. Both meters can select the stimulus voltage with a resolution of millivolts, and the test frequency with 4 digit resolution. They both display the measured values with 7 digits; the basic accuracy of the meters (.05%) can't justify so many digits, but all those digits allow matching capacitors to much closer than .05% if that is wanted.
For my first post, I'm going to show something that is not earth shaking, but is well known, though not often shown as actual measurements. Tranformers that have iron cores such as OPTs for vacuum tube amplifiers exhibit winding self inductances that vary with measurement voltage. Here are the measured self inductances of the primary (secondary open) of a Softone output transformer: Softone RX-30-8 Push-Pull Audio Output Transformer with 4 different applied measurement voltages. The first 3 measurements are made with the Hioki, which shows 4 parameters at once; this is feature I like.
Here is the measured self inductance of the primary at 20 Hz, with a stimulus voltage of 1/10 volt:
Here is the self inductance with a stimulus voltage of 1 volt:
Here is the self inductance with a stimulus voltage of 5 volts:
Finally, the self inductance with a stimulus voltage of 20 volts. For this one I used the Keysight meter for its higher stimulus voltage capability:
It's late, but I'll have more to say tomorrow.
For my first post, I'm going to show something that is not earth shaking, but is well known, though not often shown as actual measurements. Tranformers that have iron cores such as OPTs for vacuum tube amplifiers exhibit winding self inductances that vary with measurement voltage. Here are the measured self inductances of the primary (secondary open) of a Softone output transformer: Softone RX-30-8 Push-Pull Audio Output Transformer with 4 different applied measurement voltages. The first 3 measurements are made with the Hioki, which shows 4 parameters at once; this is feature I like.
Here is the measured self inductance of the primary at 20 Hz, with a stimulus voltage of 1/10 volt:
Here is the self inductance with a stimulus voltage of 1 volt:
Here is the self inductance with a stimulus voltage of 5 volts:
Finally, the self inductance with a stimulus voltage of 20 volts. For this one I used the Keysight meter for its higher stimulus voltage capability:
It's late, but I'll have more to say tomorrow.
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