SRV Calibration in AUTO mode with Mark V


I do not have a Mark V, Mark VI or Mark VIe system nearby to check for myself what I want to know. That's why I resort to asking it here.

When I have to calibrate the Speed Ratio Valve (SRV) with a Mark V control system in MANUAL mode, initially I have to change the regulator type of the SRV (which, originally, I think is 77) by the regulator 43 (the same regulator of the GCV). After the calibration is completed, the regulator corresponding to the SRV is placed back into the system. My question is: should I make that change if I do the calibration in AUTO mode? Or the system is responsible for doing what corresponds without any intervention on our part.

And the calibration of the SRV with a Mark VI or Mark VIe in AUTO mode, would be the same procedure as with a Mark V in AUTO mode?

Kind regards,

Yes; Mark V AutoCalibrate automatically changes the servo-valve output regulator type from a Type 77 to a Type 43 when an SRV is selected. And, when the work on the SRV is complete and AutoCalibrate is exited, or another servo-operated device is selected, AutoCalibrate automatically returns the regulator back to a Type 77 from a Type 43. (A Type 77 regulator is a pressure control loop with position feedback. A Type 43 regulator is a position control loop. If you pass a reference to a Type 77 regulator, it will be looking for pressure feedback--because the reference from the CSP for the SRV is in pressure. The SRV would just go full open with a reference and 0 psig (barg) feedback; that's why the regulator type has to be changed to a position control loop, and the reference, in percent (of position) can then be compared to the LVDT feedback for control of the SRV.)

>And the calibration of the SRV with a Mark VI or Mark VIe in
>AUTO mode, would be the same procedure as with a Mark V in
>AUTO mode?

The procedure the user performs differs from that of the Mark V. AND, the way the pressure control loop function of P2 (Interstage) pressure control is performed is different in most Mark VI's and Mark VIe's. The pressure control portion of the SRV control scheme is accomplished in application code (the "CSP" of the Mark VI and Mark VIe). And the output of that control function, in percent, is passed to a position control loop (essentially a Type 43 regulator in Mark V terms). So, no; neither the Mark VI nor the Mark VIe changes the SRV regulator type for MOST SRVs. (I believe there were some early Mark VI control systems that still used pressure control-with-position feedback regulators, so as with most things GE-related, there are no absolute guarantees).

Hope this helps!

I am very satisfied with the first answer about Mark V calibration in AUTO mode, and although I have to investigate a bit more about calibration on Mark VI and Mark VIe, I could get very useful information "hidden" into your explanation: I was always wondering what did the application code mean or how could I handle it. I can interpret, from you answer, that application code in Mark VI/Mark VIe is equivalent to the the CSP (that I know better) in Mark V, and that is very important to me.

Well, I will investigate a little more about the calibration of the SRV with Mark VI/Mark VIe. I think that is not a big deal, but I want to make sure of all these procedures to execute them when necessary without even think of it.

Thanks a lot.

Really useful thread to understand the regulators mode. I've never performed a manual calibration before, where should I change the regulator type for the SRV? In the ACLIB.DAT file? if so, how is coded? I read "regulator type" <D0A 19> (H1).

Thanks so much in advance.

For a manual SRV LVDT calibration you would change the regulator type from a Type 77 to a Type 43 in the I/O Configuration (for SVO1), save the changes, download I/O Configuration to the control processor(s), reboot the control processor(s), manually stroke the SRV to determine if calibration is required, manually stroke the SRV to obtain the 0- and 100% stroke voltages if required, put the 0- and 100% stroke voltage values in the I/O Configurator (after averaging them, if necessary), save the changes, download I/O Configuration to the control processor(s), verify the accuracy of the calibration, change the regulator Type back to 77 from 43 in the I/O Configurator, save the changes, download the I/O Configuration to the control processor(s), and re-boot the control processor(s).

That's all.

AutoCalibrate is SO much easier. Use the Manual feature of AutoCalibrate to determine if calibration is required and to determine the minimum- and maximum mechanical stop values of the SRV, perform an AutoCalibrate if necessary, obtain the newly-determined 0- and 100% stroke voltages from the AutoCalibrate Display (average them if necessary), put them in the I/O Configurator, save the changes, download the I/O Configuration to the control processor(s). No need to even reboot the control processors after the I/O Configuration download; the most perfect 0- and 100% stroke voltages are already in TCQA RAM, and you downloaded the (average) values to EEPROM so that if the processor(s) get(s) rebooted the new (average) values will be loaded into RAM.

The only thing(s) that need changing in AutoCalibrate are the minimum- and maximum positions of the SRV (if necessary) for performing an AutoCalibration of the LVDT feedback. AutoCalibrate doesn't set the regulator type; the I/O Configurator does that. AutoCalibrate reports the regulator type, from querying the TCQA RAM, which gets its regulator type from EEPROM during boot-up.

Hope this helps!

Thanks, this really helped. After I wrote the post I realized that the regulator type was editable from the IOconfig. I didn't know that when we perform an Autocalibration, we don't need to reboot the processors.
Currently we have the Mark V running with the interface TMOS. On this new one we missed the "verify current" and "verify position" features, so no more plottings available. How could this affect in the verification of the proper LVDT calibration?

Thanks again!

Verify Current and Verify Position are not necessary for verification of proper calibration. They are useful for troubleshooting problems to determine if the LVDT output is non-linear or the servo spool might be sticking or the hydraulic actuator might be worn or sticking. They are troubleshooting tools, not calibration verification tools (despite the names).

Refer to the Mark V manuals for details of how each tool works; but I believe the manual descriptions fail to mention that AutoCalibrate must be executed before either tool can be used. So it's very important for the 0- & 100% stroke voltages be recorded before and after AutoCalibrate is executed in the event that an LVDT, servo or actuator problem causes an improper AutoCalibration.

Verify Current and -Position have also been discussed several times on