07-11-2012 05:44 PM - edited 07-11-2012 05:45 PM
For my application, I am using a NI 9157 cRIO chassis equipped with the following types of cRIO modules: NI 9213, NI9229, NI9239, NI9217 and NI 9219.
I am concerned with the calibation procedure of those modules. I read carefully the different "Calibration procedures" made by NI for each of the cRIO modules. For instance the "NI 9213 calibration procedure".
What I understand is that it is only possible to verify the module by myself. I mean by "verify", checking that the measurement error of the module is within acceptable limits.
It is not possible, without submitting the device to NI, to perform a "factory calibration". I mean by "factory calibration", changing the internal calibration constants of the module. It seems that a "factory calibration" can be done only by NI.
My company has its own calibration lab, meaning that we are used to "calibrate" (and not just "verify") all our acquisition systems. We do not want to rely on NI for that service.
Have I correctly understood the calibration manual? Is it really impossible to do a "real factory calibration" by ourselves on the cRIO modules?
This would mean that we must send the cRIO modules to NI (and pay the corresponding service) every time we have to calibrate (and not just "verify") them?
Or maybe it is impossible to self-calibrate a cRIO module because they are all extremely stables meaning that it recommended to verify them once a year but that it is very unlikely that they do not operate within their correct range? In that case, having to send the modules to NI is very unsual and means that the module is probably out of order and should be repaired (rather than only calibrated)? I would be surprised if it was the case because most of the acquisition systems I know must be regularly calibrated to preserve their accuracy (including most of the NI equipments such as M-series).
I woud be very grateful to anyone who could answer those questions!
07-12-2012 11:50 AM
In applications I have been involved in we did calibrate our critical sensors (plus their cRIO module implicitly) - simply by setting the system to a certain known points and linearly scaling the produced signal (e.g. for a 4-20mA) to give the required engineering values. We may have to do this periodically if our sensors drift, but we are not worried about the re-calibration of the c-series modules themselves, as that level of accuracy is not needed.However, sounds like you need something more precise.
You know NI can calibrate the modules - but isn't appropriate. I have seen that some modules do have a self-calibration function, and that some state that the calibration could be done by a third party "This procedure replaces all calibration constants in the EEPROM and is equivalent to a factory calibration at NI" and is described
Hope this helps,
07-12-2012 04:54 PM
Thank you for your answer.
Andy Clegg wrote:I have seen that some modules do have a self-calibration function, and that some state that the calibration could be done by a third party "This procedure replaces all calibration constants in the EEPROM and is equivalent to a factory calibration at NI" and is described
- This doc http://www.ni.com/pdf/manuals/372676a.pdf seems to describe a calibration procedure for the NI 9213 one of the ones you have
- If you look on the ni website for the page associated with each module, click on resources, click on manuals, then the calibration docs seem to be at the bottom of the list
This is the key point of my issue. I reproduce below an extract of the "Calibration procedure for the NI 9213" you mentioned:
Calibration Process Overview
The calibration process consists of the following steps:
1. Initial Setup—Configure the device in NI-DAQmx.
2. Verification Procedure—Verify the existing operation of the device.
This step confirms whether the device is operating within its specified
range and whether it needs adjustment.
3. Adjustment—If the device does not fall within the desired
specifications, submit the device to NI for a factory calibration to
adjust the calibration constants.
4. Verification Procedure—Perform another verification to ensure that
the device operates within its specifications after adjustment.
The first two steps are explained in the following sections.
This manual states that only "Verification" can be performed by ourselves. We can not do "Adjustement" (i.e. adjusting the internal constants of the module at the hard level). This "Adjustement" corresponds to replacing the calibration constants in the EEPROM. This "adjustement" can be done only by NI. This is however possible on most of the other NI equipments (M-series for instance).
I really do not understand why it does not seem possible with C-series ?
This is a real issue for us as we calibrate separately the sensors (pressure transducers for instance) and the data acquisition system (C-series here). By doing this, we can use the same sensor on different data acquisition systems. Of course the best accuracy can be only achieved if the C-serie module can really be calibrated ("adjusted"). This does not seem the be the case here...
07-12-2012 06:19 PM
The manual's introduction does imply that the calibration can be done somebody other than NI, but from what you quote it seems that this is not the case. I hope somebody from NI can give an insight into this.
07-18-2012 09:43 AM - edited 07-18-2012 09:52 AM
Accordingly to the calibration procedure of these devices :
You can made it yourself with : 9219 ( http://www.ni.com/pdf/manuals/372264a.pdf )
You can't made it yourself with : 9213 , 9217 , 9229 , 9239 (You don't have the calibration manual for the Adjustment for these devices)
I hope it's what you wanted to know !
PS : You can have, for certain devices, the free calibration with the warranty.
07-25-2012 11:48 AM
Ok thank for your answer. This is the confirmation I needed. At least this is now clear.
This is a pity that it is not possible to perform suche a "basic operation" as a full calibration without the assistance of NI.