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calculate pulse signal / raw tacho from existing analog tacho trace

Experimenter
Experimenter

I need some help to apply the RPM_TO_TACHO_PULSE-function to a motor speed signal using the Time Signal Calculator.

When use the formula/function like this    RPM_TO_TACHO_PULSE(CH8;1;1;0;0;DEFAULT)

 

the follwoing message is returned: Formula1: <Position 1> Internal error . ; CH8 is the analog speed signal within the imported data set.

 

How can I make this work?

 

This I need to create a raw tacho trace to enable order tracking in Time Data Processing of Test.Lab.

 

 

2 REPLIES

Re: calculate pulse signal / raw tacho from existing analog tacho trace

Siemens Valued Contributor Siemens Valued Contributor
Siemens Valued Contributor

I think you want to use TACHO_PULSE_TO_RPM.  That will give you an RPM vs. Time curve and the RAW Tacho you need for Order Tracking.

Re: calculate pulse signal / raw tacho from existing analog tacho trace

Siemens Phenom Siemens Phenom
Siemens Phenom

Hello,

 

We've been getting this question lately.  If your channel is already in rpm units and you don't have the "raw tacho" trace which includes the tacho moments (trigger crossings of the pulse) then you cannot do order tracking or angle domain processing with that tacho channel.

 

The workaround, and be careful because it is not as accurate as using the tacho moments is to take your original tacho rpm, make sure it is in the Tacho group and then use the RPM_TO_TACHO_PULSE command to generate pulses.  I noticed your pulse width was zero, I normally use 10-20 percent so I can see the pulse.  Then use the TACHO_PULSE_TO_RPM command to generate the RPM trace again and overlay with the original to see how close it is.  You can then tweak the parameters if needed.  I notice your rpm channel is CH8, so the commands would be as follows.  If you do not move the RPM channel into the Tacho group you will get the error you saw concerning "<Position 1> Incorrect channel provided for tacho!."

11-10-2017 2-05-06 PM.jpg

 

Make sure the resulting RPM trace closely matches the original if you plan on using Order Tracking or Angle Domain processing.  See the differences I experienced here:

 

11-10-2017 2-11-05 PM.jpg

 

 If you need further assistance, please reach out to your local Global Technical Assistance Center (GTAC) team.