DLA1500I pure sine wave

[pipenik]

I've searched the internet and haven't found anything specific.
I have two UPS
1. APC Smart Ups DLA1500I
2. APC Smart Ups SUA750I
And a Junkers Cerspur Smart gas oven - UPS's were to be maintained in the event of frequent memory failures. With the APC Smart Ups 750I, there is no problem keeping the furnace running after a power outage. However, with APC Smart Ups DLA 1500I, after a power failure, the stove shows an error.
Do both UPSs have a variable sine wave, because such a UPS requires a stove.
From what I can find parameters on the net, yes. But in practice, probably not, because the 1500 behaves as if it did not have it. How to possibly check it?
Maybe someone can help.
I will be grateful.

APC Smart Ups DLA1500I

S/N: AS0625212936

[BillP]

@pipenik 

DLA is the equivalate to a SUA and will have a pure sinewave. To test, an oscilloscope would be the best to verify the sinewave.

[pipenik]

Ok, I will try to check it. But UPS is working properly when it is plugged in. It works not properly when it works on batteries,when there is no eletricity. Maybe you know what could be a problem.