Brushless DC motor Tacho measurement cDAQ-9174

[Simon-lee]

Hi Folks,

I’m trying to monitor the speed of brushless DC motor (Thomas 1410 series 12v). using a cDAQ -9174 chassis.

The motor runs as expected but when I attach an oscilloscope to the Tacho output I’m only seeing signals between 0.3v and 0 (but at the correct frequency).  

Is this enough of a signal to bring directly into the chassis (what module would people recommend)?

If not, what should I do to the signal to achieve the 0-5v TTL described in the spec sheet?

(again, what module would be best suited?)

Please excuse my inexperience as I’ve never played with frequency measurement before.

Regards

Spec sheet and Brochure attached 

[Winnie_G]

Hi there,

No that is not enough voltage for cDAQ to read. Depends on your specific application, I would recommend you call your local NI Sales representative for module recommendation!

Thanks

[Simon-lee]

Hi Winnie_G

Thanks for your interest.

My boss overcame the low voltage problem for me.

I not saying he's old school but he still laments the passing of the valve, he put together a small discrete amplifier.

I've run it against the scope and its noisy as hell but it works.

Many thanks

Si 

[Antoniooh]

You may have partially solve your problem but the real problem is that from your specs you should be getting 0 to 5V from your tachometer, if you are getting 0.3 V then something is wrong check your circuit impedance.

Disconnect the tachometer just measure its otput with an osciloscope if the output is still 0.3 then its broken.

Saludos.

[Simon-lee]

Hi Antoniooh,

Your 100% correct, these motors are up to specifcation.

Unfortunatly our supply chain has take a massive hit and I doubt I can get any replacements.

On the plus side the taco was only used for testing and we will flag these units as requiring a recall as and when the situation recovers.

Regards

Si