My ET5410A+ arrived on September 2nd, 2024.
The device without cable weighs 2923 g.
First I checked the accuracy of the voltage measurement.
When the inputs are open or short-circuited, 0.012 to 0.019 V are displayed. It changes slightly when switched off and on again.
With a connected battery, an exactly the same voltage of 13.755 V is displayed compared to the OWON XDM1241 (accuracy 0.05%). A 10V reference voltage is measured once at 10.006 V and a little later at exactly 10,000 V.
This was followed by a check of the current measurement in the range up to 11 A, the XDM1241 cannot do more than that. It was noticeable that the load does not always regulate the setpoint exactly. The largest deviation of 0.23% between the two displays was at 7 A. However, the OWON is only specified with an accuracy of 0.5% in this range.
The next test was the contact resistance up to the circuit board. To do this, I connected the terminals with a solid copper wire and measured the resistance between the circuit board points with the DE-5000 from DER EE; it was 3 mOhm.
Now for the modification with sense inputs. I don't like the solution with a switch because I expect contact resistance in the long term. You also have to pay attention to the switch position.
I prefer the solution with two low-resistance resistors and have calculated their measurement error. As a result, I decided on 10 Ohm resistors.

This results in a small additional error of only -0.005% for 2-wire measurements (e.g. -0.6 mV at 12 V or -2.4 mV at 48 V). This is negligible compared to the error that typically occurs due to the resistance of the wiring.
When measuring with 4 wires, you should also pay attention to low-resistance measuring cables, otherwise the voltage drops in the load cables will affect the measured value via the 10 ohm resistors. If you have to deal with longer cable lengths, you should choose the 22 ohm variant, as this will result in an additional error of -0.011% in 2-wire operation.
I am attaching the calculation with both variants here and hope that it is presented in an understandable way. Please see the attached "
error-calculation.pdf".
In a 30 A load test with very good load lines (2x 10 AWG parallel, approx. 10.5 mm² Cu, only 0.27 m long), the additional sense lines produced voltage values about 50 mV higher.