Linear Technology is great for understanding the advancements in digital filtering... Nyquist limit and aliasing are so very important.
I would say filtering is 90% of the equation and sample-n-hold is the other 10%
Speaking of which (work) the cost-benefit analysis of doing both HV measurement and isolation tests came up with the following:
1) USE a COTS PCB from a low cost auto-ranging DMM ($10)
2) Power it from Isolated DC-DC and communicate with it via digital isolator ($10)
3) Multiplex it with SPST 1KV rated reeds @ $3 each, 6 needed minimum $20
4) HV considerations so a larger PCB - piggybacked
Engineering of a reliable HV measurement is not on the table... so...
Combined with CAN communciation, isolation mesurement, precharge, and contactor drive
Available signals required are B-, Chassis, P+ (B+ AFTER contactor), AUX power/ground (12V or any other isolated signal)... B+ required for Precharge
All signals avaialble
Matrix is
B- to Chassis
B- to any AUX
P+ to Chassis
P+ to any AUX
Where dual failure (both B+ and B- to Chassis or AUX) is detected as a voltage divider
Where 100Mohms is way more insulation that we can reasonably expect when counting all the datasheets up in the system
Where the measurement is diode isolated (for the Linear ADC approach) and bi-polar for the DMM approach (eliminating measurements)
Where no induced voltage is required (HiPot by nature) and no current or resistance measurements are to be trusted (but could be used)
where... wait... why am I writing my engineering notes online?
Oh yea... because I am not being paid... and when I am not being paid I work open source.
Speaking of being paid - I have 4 contracts now
One OEM Startup in Fremont
One Robotics in Palo Alto
One Sevcon related in La Selva Beach
One LabVIEW (by far my favorite at the moment)
So... as soon as I can make the BMS contract pay... we are off and running with a full schedule of 40hrs a week.
Currently the BMS project pays only in parts, support, design review, production help, and outlet
Its a HORRIFIC effort to get right in the face of multiple OEM examples and a few COTS examples...
Where looking to make Lego parts which can play nice with others, impede no one, possibly make it into an OEM lineup, and not cause us to go broke.
thanks,
-methods