Micrologix 1400 PWM behavior

I have a couple of questions regarding the PWM output on a Micrologix 1400 BXBA. The 20 KHz output shown in the attached photo is being fed to a high speed counter input. The low level is roughly 12 volts which is not low enough (1.5 volts) for the input to recogize it as "off". Is there a way to configure the PWM output to be used with a high speed counter input?

The other question to reveal my ignorance, is that if I instead route the output accross a resistor of any value, my scope does not see the square wave but a constant 24 volts.

Any insight would be most helpful.

Walt

I can't really help you without knowing how you have it wired. Draw out the entire circuit and show precisely where you are measuring from.

PWM on the 1400 should be able oscillate from +24V to near 0V if it is wired correctly.

■ COM 0 ------------- -24 ----- scope
■ IN 0 ------------------------- connection
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■ OUT 2
■ VDC 2 ------------- +24

Thanks

Your scope should be on the negative supply of the 24 volts (COM2) and OUT2 (assuming you are using OUT2). But you aren't showing a COM2 connection in your diagram.

Attached is a more definitive wiring diagram. A bit confused by your reference to COM2.

Walt

COM 2 on the output terminal block needs to be tied to 24VDC common, just like COM 0 is in your diagram.

Yes, that fixes everything. Thank you very much.

Walt