For “CURRENT LOOP”
The video is Dynamics Circuit's video about calibrating 454a,From the video, "CURRENT LOOP" is specially prepared for external resistors.But (https://www.ebay.com/itm/3035985129...338722076&customid=&toolid=10050) this seller sells 125OHM external load without "CURRENT LOOP" pin.i don't know why.

For ESU-2050
It seems to me that it is just a host, and there is no built-in load resistor.If you want to achieve the same test load resistance value as 454a or QA-ES ii, iii, it will be very bulky.ESU-2050, ESU-2300 they look more like the continuation of 454a, because they all use current transformers

For DSP
Using DSP technology in the ESU analyzer, I think it's more of a gimmick。The use of DSP technology will definitely improve the accuracy of analyzer measurement and the perfection of waveform.For the accuracy, I think it is good to be able to reach 2%-5%, and I think the accuracy of 1% has no practical significance,Because the load resistance is difficult to achieve 1%, even if the temperature change is achieved, the accuracy will be affected,Reliability and portability are more important than accuracy

For Fluke 8920A
8920A is a very good meter,Its 20M bandwidth has not been surpassed so far.(After the discontinuation of production, many ESU manufacturers use RHODE & SCHWARY URE 3 for calibration),Especially for the analysis of Jianfeng waveform, it uses the same heat conversion principle as 454a, I think this is objective and scientific.Maybe the LT1088 discontinuation is the main reason.I also have an 8920a that I've been using and it's been pretty accurate over the years

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