That’s the same VT I’ve been using in all my stm32 experiments with the emontxshield demo stuff (STM32 Development). So I can add some data, at least for my specimen. My no-load voltage ratio is almost exactly 1:23, i.e. when I put in 230V I get out 10V. And my overall VT+emontxshield voltage ratio is almost exactly 300. When I put in 230V I get out 766mV. The transformer divides by 23 and the shield divides by 13 (nominally), for a total division of 299 (measured at closer to 300).
My phase measurements have all been relative to the SCT013 phase error, not absolute. At 230V, 10A, I found I had a net phase error of ~4.8 degrees. I then calibrated that away using the simple ADC lag technique discussed in the stm32 thread, so now at 230V and 10A I have no phase error at all.
[Section about distortion at higher voltages retracted as I’ve now discovered much of the distortion at the higher voltages is actually coming from the calibrator, which is limited to driving just 20mA on it’s V output].
In theory I should be able to bypass the VT altogether, set the calibrator to ~10V and feed that straight into the AC jack on the shield. Then the phase error will be entirely down to the CT, so I can measure that at 10A (or any other current for that matter) and then turn those relative VT phase errors into actual VT phase errors. I’ll add that to the list of things to try when I get a chance.