Made another two transformers using that salvaged VAC core. Used bifilar (non-twisted) winding, PTFE isolated.
Results
Next apply a function generator at the input, connect a 10 Ohm resistor across the output and measure voltage across that output. Sweep frequency from 1Hz (or whatever is lowest possible) to 20Mhz at a rather low level (< 1Vpp) and draw the frequency response (bode plot). This should get similar results to the posted plots. This measurement includes the loading of the transformer / 10R to the generators output and differs from the transformers response.
Next apply a function generator at the input, connect a 10 Ohm resistor across the output and measure voltage across that output. Sweep frequency from 1Hz (or whatever is lowest possible) to 20Mhz at a rather low level (< 1Vpp) and draw the frequency response (bode plot). This should get similar results to the posted plots. This measurement includes the loading of the transformer / 10R to the generators output and differs from the transformers response.
Why the 10R? Does that reflect how you most often use them?
Why the 10R? Does that reflect how you most often use them?
10R is the value the Omicron transformer is specified for (recommended 1R ,,, 10R afair). Just to be comparable - e.g. I did the measurements for my home rolled transformer with 50R termination and get different results.
QuoteWhy the 10R? Does that reflect how you most often use them?Quote10R is the value the Omicron transformer is specified for (recommended 1R ,,, 10R afair). Just to be comparable - e.g. I did the measurements for my home rolled transformer with 50R termination and get different results.
Low value load impedance Because of the way injection transformers are used. To inject the signal into the power supply control loop you break the control loop connection and insert a low value resistor in it in series across which you then connect the injection transformer. Resistor values up to 10 Ohm seem to be reasonable to not have effect or have minimal effect on the control loop under test. 50 Ohm may be too high, i'd shoot for and test with 10 Ohm.
Another reason to use a very low termination resistor for an injection transformer is bandwidth. The lower the termination resistor, the higher the bandwidth
Another reason to use a very low termination resistor for an injection transformer is bandwidth. The lower the termination resistor, the higher the bandwidth.