by dave slagle » Fri Jul 13, 2007 12:57 am
Lets start with the concept of mixing lams. I have no doubt that the proper mixture of core materials in discrete lams can yield very linear behavior under simple conditions. Both Steve bench and the person who supplied the small stash of lams have noted this. When signals become more complex, the situation becomes less clear to me.
Lets start with a mixture of 80% nickel and cobalt (hiperco50) lams. Steve noted that this mixture gave him very linear results in measured inductance over varying DC current. This suggests that the net perm remains very constant with excitation and it just so happens that the most linear of core materials is perminvar (PERMeability IN VARiable) which happens to be a cobalt nickel mixture with a special anneal.
Next up came the concept of some nickel in the middle of some steel and that is a concept i have wrestled with for some time. The claim is the nickel gives low level detail and the steel gives high level power, but I just don't see how the lams could discriminate like that. Sure, if the only thing present is low level info then the nickel would dominate, but as power comes along, then the nickel would also accept the power and saturate leaving the low level remains for the steel still left in the picture.
when you consider that the original mixed core samples were nickel steel and used for PP applications, unless there were provisions for a perfect DC null in the circuit, any DC offset would follow the path of least reluctance. (through the path with the highest perm.) Even in the case of a perfect null, I still say the larger flux levels would dominate the higher perm material which on the surface flies in the face of the "simple" argument that the nickel would handle the low signals and the cobalt the power. Sure it makes for good marketing speak, but i',m more interested in a discussion in what is really happening and we have a situation where some ears on data can be added into the mix to confirm or deny in a statistically insignificant sample of one.
more to come
dave
Lets start with the concept of mixing lams. I have no doubt that the proper mixture of core materials in discrete lams can yield very linear behavior under simple conditions. Both Steve bench and the person who supplied the small stash of lams have noted this. When signals become more complex, the situation becomes less clear to me.
Lets start with a mixture of 80% nickel and cobalt (hiperco50) lams. Steve noted that this mixture gave him very linear results in measured inductance over varying DC current. This suggests that the net perm remains very constant with excitation and it just so happens that the most linear of core materials is perminvar (PERMeability IN VARiable) which happens to be a cobalt nickel mixture with a special anneal.
Next up came the concept of some nickel in the middle of some steel and that is a concept i have wrestled with for some time. The claim is the nickel gives low level detail and the steel gives high level power, but I just don't see how the lams could discriminate like that. Sure, if the only thing present is low level info then the nickel would dominate, but as power comes along, then the nickel would also accept the power and saturate leaving the low level remains for the steel still left in the picture.
when you consider that the original mixed core samples were nickel steel and used for PP applications, unless there were provisions for a perfect DC null in the circuit, any DC offset would follow the path of least reluctance. (through the path with the highest perm.) Even in the case of a perfect null, I still say the larger flux levels would dominate the higher perm material which on the surface flies in the face of the "simple" argument that the nickel would handle the low signals and the cobalt the power. Sure it makes for good marketing speak, but i',m more interested in a discussion in what is really happening and we have a situation where some ears on data can be added into the mix to confirm or deny in a statistically insignificant sample of one.
more to come :-)
dave