MS3 and maf - question

[Yves]

I just wired up my ls1 maf to the ecu. At first I forgot the pull up resistor and connection with Vref. It gave me a frequency reading but no movement when I pulled air through the inlet tube with a vacuum cleaner. When I attached the pull up + Vref to the signal wire, I got it to move with the airstream. So far so good but what makes me wonder is that the gauge in the maf flow curve screen shows voltage...I thought that these mafs didn't output a voltage ? The voltage varies with airflow apparently...