My SDL1020X-E arrived last Thursday. I bought it from Eleshop (
http://www.eleshop.nl), and they promised me I could test it for a while, and return it if I didn't like it. So far I tested the DC performance. The burning question is of course: although it's an X-E, does it actually meet X spec? The X model has better specifications on the accuracy of current setpoint in CC mode, and on voltage readback. The specs I refer to are from the March 2019 datasheet, the interesting bits are:
- CC setpoint: (0.1% of value + 0.1% of range) for the X-E versus (0.05% of value + 0.05% of range) for the X
- Voltage readback: (0.05% of value + 0.02% of range) for the X-E versus (0.025 % of value + 0.025% of range) for the X
Apart from this, the X provides one more digit in the readout of voltage (low range only), and in the readout of current (both low and high range), but I am 99.9% certain that this is only a matter of software and not due to a hardware limitation.
Voltage readback was easy to check. My bench DMM has better DC voltage accuracy spec than the X, so a direct comparison should be sufficient. I can put down a long winded measurement report, but I'll just give you the executive summary. With voltage readback, the largest error I found in low range was 1/6 of the allowable error for the X. In high range, the maximum error was 1/3 of the allowed error (for the X) up to 120 Volts, at 150 Volts it was still 1/2. The measurement at 150 Volts was done with the DMM in 1000V range, so there is a good chance that actual error is smaller than the error I found. Conclusion: the voltage readback accuracy on my unit meets X spec. Yay!
CC setpoint was also easy to check. Although my bench DMM does not provide the required current range and accuracy, the current readback spec on the load itself allows testing. The accuracy spec on current readback is (0.05% of value + 0.05% of range) for both X and X-E models. So if I set a current, and get the exact same value back on readback, I can be sure that the setpoint accuracy is within readback spec. For the X, setpoint and readback spec are identical. That makes sense, because the current setting and current readback share many components (shunt, PGA and whatnot), so actually many error sources are also shared. This means that a current readback that is bang-on the current setpoint proves that the instrument meets X spec, but only a deviation between setpoint and readback value larger than (0.05% of value + 0.05% of range) proves that it does not. The area in between is a grey area. But again, here comes the management summary: in both low and high current ranges, the current readback value and the current setpoint were identical. In low range I tested between 10 mA and 5 A, in high range I tested between 1 A and 30 A. So current setpoint accuracy on my unit meets X spec. Double yay!
I also tested the impedance of the short circuit, which represents the lower limit of usability of the load. For this test, I measured the voltage on the clamps of the load with my DMM using separate leads (i.e. a proper Kelvin connection). From 5 A to 30 A, I found the load presented a practically constant short circuit resistance of 26 milli-Ohms. The spec works out to 30 milli-Ohms, so that's good too.
I ordered some low-value resistors and other hardware so I can test dynamic behavior. I'll keep you updated on my findings.
To wrap things up: my unit appears to meet X specifications in terms of current setpoint and voltage readback, although it is an X-E.
I really wonder what Siglent wants with the X. The accuracy spec for voltage readback is (0.025 % of value + 0.025% of range). With a readout resolution of 0.1 mV for the 36 V range, this becomes (0.025 % of value + 90 digits). For the current ranges (0.05% of value + 0.05% of range) at a resulotion of 0.1 mA becomes (0.05% of value +25 digits) for the low range and (0.05% of value +150 digits) for the high range. With the findings above, does this really mean that they charge you around 160 Euros (excluding VAT), just for the privilege of looking at one or two random digits?