Missing pulse detector

Hi to the forum.
I have an AC inverter with current speed as a pulse or analog output - standard on most drives. I have a sensor on a turntable. I need to make sure the table is rotating no mechanical slippage. I was going to use a siemens logo. The input resets a timer if the timer ever times out then the turntable is not turning. I was going to use the analog speed reference as the timer setpoint as they can vary the speed of the drive.

I was wondering is there a timer out there that has a pulse train input or analog setpoint as this would be so much easier or can anyone think of a easier or more cost effective way.

How fast are the pulses? If they're slow enough for the PLC to catch all the transitions, then your theory of operation will work fine.

You can get fancy and calculate the timer preset for the maximum pulse delay if the same PLC controls the speed and it varies alot, then I would definitely do that. But, if you are only monitoring and you need something lightning quick and that will handle a wide variety of circumstances, then you might want to go about it differently.

Some drives offer a shear pin fault which can detect a pretty short duration spike in the load and shut down. This would probably only be useful if the load (as seen by the drive) is pretty smooth and repeatable.

If the pulse on and off cycles are uniform, then a single timer will suffice. If they're not, then you may want a timer for the on dwell and a timer for the off dwell.

I have done this in a PLC by having the timer run whenever motion is commanded or expected.

Then, every transition of the input pulse resets the timer (oneshot rising and oneshot falling).

If the timer times out a fault has occured.

Thanks OkiePC looks like I'll need a smart relay or small PLC. To be honest I was going to use the analog output from the drive into the Pico or Logo 0-10V input there I think your dwell timer idea is excellent.
I am still thinking about the Omron drive and trying to monitor the current maybe. Our biggest concern is if the mechanical linkage breaks and the drive carries on running with no warning. The parts on the turntable are expensive.

Some drives have a selectable underload fault. If the turntable likely stops due to something in the power train breaking (belts off, coupling broken), the motor will unload to a lower current than if it was turning the table. You could set the underload detector so, after a selectable number of seconds at a low current, the drive faults.

This would not be suitable if jamming (overcurrent) is a likely cause or if the normal operation of the machine causes periods of very low load or current.