I have a ML1400 BXBA. I wire the 24V to th VDC2 and 0V to the Com2. And I tried to produce a square wave of 50% duty cycle with frequence 100Hz. My DC drive cannot read the signal. So I checked with the meter, the waveform is not sqaure and the Vrms is almost 0. When it is like 5Hz, the voltage is higher. The Vrms should not affected by Freq. So do I have a faulty PLC?