Re: MRES and friends

["Jemian, Peter R via Tech-talk" <tech-talk at aps.anl.gov>]

Pete:

Adding to Mark's reply, I put your original email into https://urldefense.us/v3/__https://deepwiki/epics-modules/motor__;!!G_uCfscf7eWS!ZPiZadYfDmipdEg6Dqj27vmkFMBNgdaaYGh7Ye4BM_ynjXRY-69xpjZWRejNhkzP0fAOh4lxAxWq9nD5T-Tk$  and got this LLM-assisted reply:  https://urldefense.us/v3/__https://gcc02.safelinks.protection.outlook.com/?url=https*3A*2F*2Fdeepwiki.com*2Fsearch*2Fi-am-confused-by-the-mressresu_5d9ff368-d12a-478f-bbe1-12a680fb8526*3Fmode*3Dfast&data=05*7C02*7Ctech-talk*40aps.anl.gov*7C00f468c330254acdec6108de82c64302*7C0cfca18525f749e38ae7704d5326e285*7C0*7C0*7C639091985221109965*7CUnknown*7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ*3D*3D*7C0*7C*7C*7C&sdata=0tAQNc6mUmnFpiHtw1MhZOx1eXndR2MmM4G*2Bar5Fwg0*3D&reserved=0__;JSUlJSUlJSUlJSUlJSUlJSUlJSUlJSUlJQ!!G_uCfscf7eWS!ZPiZadYfDmipdEg6Dqj27vmkFMBNgdaaYGh7Ye4BM_ynjXRY-69xpjZWRejNhkzP0fAOh4lxAxWq9m-FbU6x$ 

Same information, more explanation.  A couple application notes and direct reference to motor record documentation.

Regards,
   Pete

________________________________________
From: Tech-talk <tech-talk-bounces at aps.anl.gov> on behalf of Mark Rivers via Tech-talk <tech-talk at aps.anl.gov>
Sent: Sunday, March 15, 2026 1:00 PM
To: Mark Rivers via Tech-talk; Siddons, David
Subject: Re: MRES and friends

Hi Pete,


  *
I am confused by the MRES/SRES/URES trio in the motor record.
  *
MRES is obvious, and for me this seems to be the only one of the three needed, and should be in EGU/step. What are the use cases that need the other two? OK, if the drive has microstepping, that changes the steps per resolution as well as the EGU/step, but so what?

I think you mean SREV and UREV, not SRES and URES.

MRES is user-units per step
SREV is steps/revolution
UREV is user-units per revolution

MRES = UREV/SREV

Many users find SREV and UREV more descriptive of the drive train, and so we use these in the template file.

For example if I am using a conventional 2-phase stepper motor with 16x micro-stepping, and a 2 mm pitch lead screw then I use:

SREV = 200*16 = 3200
UREV = 2.0

I find this more intuitive and easier to understand than

MRES = 0.000625


  *
This question is not specifically for Mark, but Outlook insists it go to him, don't know why.

It doesn't really go to me directly, it is just that Outlook has associated tech-talk.aps.anl.gov with my name.  That happens to me for other users as well from time to time.

Mark


________________________________
From: Tech-talk <tech-talk-bounces at aps.anl.gov> on behalf of Siddons, David via Tech-talk <tech-talk at aps.anl.gov>
Sent: Sunday, March 15, 2026 10:13 AM
To: Mark Rivers via Tech-talk <tech-talk at aps.anl.gov>
Subject: MRES and friends

This question is not specifically for Mark, but Outlook insists it go to him, don't know why.

I am confused by the MRES/SRES/URES trio in the motor record.
MRES is obvious, and for me this seems to be the only one of the three needed, and should be in EGU/step. What are the use cases that need the other two? OK, if the drive has microstepping, that changes the steps per resolution as well as the EGU/step, but so what?
Maybe I'm missing some key concept here 🙂
Pete.