Products > Test Equipment
XJW01 Auto LCR meter review ($120 bench top LCR meter)
nctnico:
You can calculate the capacitance and resistance (ESR) from the complex impedance. Google 'lcr meter formula' and you'll find a document from HP.
happydad:
OK, so I am assuming that the generator is putting out sine wave so we can get phase information from reading back V & I? A lot is hidden in the software, and I'm still trying to figure out how you extract phase information.
happydad:
From what I've read, in order to separate out the real and imaginary components from what was measured, we have to multiply the V and I by the signal generator, at both 0deg and 90deg. For education purposes, where is that implemented in the attached schematic? If I were to do a brief walk through, we have 6th-order LC filtered DDS sine wave ac coupled and buffered generator driving the DUT. We then measure the differential complex voltage (and current) through TL084 opamps, gained up by 2 and rc filtered through 1kohm and 470pF, and then running it through a programmable gain stage, then another 3x buffered stage to another differential TL082 with PA0 and PA1 ports. Here is where I am not sure what is going on. Are we trying to flip the sign here? If so, it's 180deg and not 90. Maybe the 180deg flip is to get rid of the reactive component? Very confused. Please help. Thanks.
nctnico:
That schematic isn't from the XJW01 !
This thread has some info on how an LCR meter works (an LCR meter actually has a lot of similarities with an impedance analyser):
https://www.eevblog.com/forum/projects/impedance-analyzer-build-and-experiments/
timofonic:
I wonder why aren't there a DIY high end bench DMM. Are they so difficult beasts.
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