If you look in the specifications for the AC source you will see that for the VA measurement accuracy. there is a minimum offset term of 1.5VA no matter what the output is. Then there is a second term which is based on output voltage, shown as 1.2mVA/V. You must multiply the output voltage times this term and it gives you a second term. So for an output voltage of 220V with no load for example, the result is 1.2mVA/V * 220V = 0.264VA.
From the specification this would yield a VA reading at zero current from 0 to 1.764 VA as being a valid reading.
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