Greetings,
I was looking for research papers, sites and books that dealt with impedance/LCR measurements. When the first patent on the list popped up.
https://patents.google.com/patent/US20150028892 "Digital multi-meter with LCR function"
Yes the patent is for a handheld that can measure voltage, current, resistance, capacitance and inductance. Filed for in 2012 based on a priority to a Taiwanese patent and issued in 2015.
The only thing I see as a disclaimer is that the LCR meter has to have a impedance measuring circuit that has a auto-zero amplifier selectively coupled; But it looks like some of the dependent clauses do not require the auto-zero amp. They then proceed to basically cover just about every know method of measuring voltage, current, and impedance.
Depending on how it does it measurements for capacitance and inductance, it looks the Elenco LCM-1950 is prior art going back to at least 2006. It is a DMM that can also measure capacitance and inductance. I can see how simply adding a "auto-zero" amplifier to an impedance meter is earth shattering. I would most likely prefer a IN Amp(which may give me a bonus auto-zero for free) or Diff Amp in the chain.
Next up
https://patents.google.com/patent/US20170292988A1/en " Signal testing apparatus for printed circuit board"
Filed 2015 granted 2018. This sounds like a ATE bed of nails system.
Here is one from Japan,
https://patents.google.com/patent/JP2008516508A/en " Impedance detector "
Files 2004, granted 2011. To be truthful this sounds like a auto tuner with a fancy SWR meter for a display.
And what I think takes the cake,
https://patents.google.com/patent/US20100244868A1/en "Wireless Clamp-on Current Probe"
Filed 2009 Published 2010 Abandoned 2019
Get a DMM with current clamp probe and hook it up to a wireless bridge. I wonder if wireless telemetery would have counted as prior art? Like the status of satellite power systems?
Am I being brain dead or are these things obvious to anyone in the field at the time of filing?