Don't know if I'll have time to verify
this post today regarding the resistors for the op amp, because in order to do so, I would like to verify the sensors used for the meter.
Everyone is assuming that Hall Effect sensor(s) are in play, but my initial findings so that AMR/magnetoresistive sensors are actually employed. There are 2, 4-pin, ~1.3 mm x 2.1 mm x 0.55 mm SMDs under the nubs in the fixed jaw with the package marking of 'D'. The leads are on the long sides. Using a ziplock, boiling water, and some ice-cold cold packs, I opened up the jaw to see what was what since Joe Smith doesn't want to share his high bandwidth hack.
I have 2 UT210E's, one being donated to this hacking, both with the DTM0660 controllers. The EEPROMs are stock atm and so are the meters, but hacking in SMA connectors on each and upping their bandwidth is the intent.
I digress though, as AMR/magnetoresistive sensors are Wheatstone-based sensors. Digikey shows 2 parts that are physically close match with similar "resting" resistances of ~260 ohms, the HW105A and the HW108A, with the 105 being the one that matches physical and electrical checks. I'm looking for similar/equivalent parts that are still in production to see if I can get more details specs such as identifying if they have particular qualities that would limit bandwidth. If not, then it is solely up to the OPA4330 and the circuit design that is the bandwidth limitation, yes?
Pictures will arrive when I have time to take them and have looked into the op amp channels and associated gain on all 4. Oh, one more myth to dispel, the ground/guard lead that goes into the fixed jaw, solder point 'A1' is for NCV. It is not a guard.