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08-31-2015 09:12 AM
hi,
I use TDMS Set Properties VI to save the result .
I use a Numeric double, but want the data to be in SI (m,n k....) format with specific Precision length. eg 0.0025643678 = 2.564m
any way to achieve this
Type casting doesnt seem to work
regards
Akshay
09-01-2015 12:35 PM
Hi Akshay,
You raise two issues here. The first is that custom properties in a TDMS file (as of 2015) do not have a built in mechanism to store the engineering unit of the property value. The only way to clearly indicate that is with a property name suffix:
Pressure_Pa
EngineSpeed_RPM
ElapsedTime_s
The second question you raise is how to achieve the desired precision of the stored property value. If you're storing a DBL data type property, then you usually have enough precision in the data type to encode the exact desired precision of your measurement. If you use smaller footprint data type properties, such as SGL, I16, I8, then you may well run out of available precision in the data type you're using, such that trailing zeros after your known measurement precision may not be possible. If you put the unit in the property name as suggested above, then you can at least scale the property value so that it's close to 1 and therefore makes good use of the data type precision you have.
Brad Turpin
DIAdem Product Support Engineer
National Instruments
09-02-2015 08:11 AM
Thanks Brad for response,
I was not specific in saying that "SI Notation" -> display format for a Dbl & not SI units.
it automatically adjusts the data & saves space.
as a response to your 2nd point I just want to use the TDMS Set Properties VI only witha double..
I cant get why I cant change the precision of my data that is saved in TDMS file.
regards,
Akshay
09-07-2015 04:35 PM
Hi Akshay,
The data type of the wire in LabVIEW will determine the data type of the property in the TDMS file. If you want to reduce the precision of the property value to just a few digits, just make this happen in LabVIEW in the wire, then save that reduced precision value to the TDMS file. Only note that reduced precision values work best as data type DBL.
Brad Turpin
DIAdem Product Support Engineer
National Instruments