Re: some proposals for future developments

["atreding" <atreding@xxxxxxxxxx>]

We generally cycle the parts a few times before we test them, so they 
will be in the proper working condition when they are tested - that 
is, the state they will actually be used in. We do sometimes see 
differences in the forces between the first time we ever cycle them 
and subsequent cycles, but it is generally a pretty small contributor 
compared to other factors at work. We have tried this method in the 
past (approaching the target current from both directions) and we do 
see some difference, but not usually enough to be significant. Using 
an ac source to demagnetize the samples might be an interesting thing 
to try - although it won't be representative of the actual usage of 
the unit. Maybe I'll give it a try next time I run into the issue and 
see what happens. Thanks.
Andy


--- In femm@xxxxxxxxxxxxxxx, Keith Gregory <k.gregory@xxxx> wrote:
> I asked about the excitation because I was thinking about 
hysteresis; has 
> it been considered?
> 
> Have you noticed any change in the force at low levels of 
excitation after 
> a solenoid has been driven to saturation?
> 
> You could try demagnetizing a solenoid using a reducing ac 
excitation then 
> measuring the low level force with dc excitation that is only 
increasing. 
> Follow that by driving the solenoid into saturation and then 
measuring the 
> low level force with a deceasing excitation. If there is any 
difference 
> between the two measurements then hysteresis is affecting things.
> 
> Keith.