Converting timestamp from TDMS LabView
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I received measurement data using LabView as a TDMS file and use TDMS reader from https://se.mathworks.com/matlabcentral/fileexchange/30023-tdms-reader to import it. The file name itself already indicated date and time of the measurement, e.g., COP_meas1_25-01-27_1237.tdms, but the resolution was only 1 s.
Using excel with AddOn from NI, I got the following results:
From values attached to this question.
Using
datetime(timestamp(1:5),'ConvertFrom','datenum','TicksPerSecond',1e4,'Format','HH:mm:ss.SSSS')
I got the following results.
05:37:04.1507
05:37:04.1520
05:37:04.1532
05:37:04.1545
05:37:04.1557
Using
datetime(timestamp(1),'ConvertFrom','posixtime')
I got
09-Jan-1970 13:27:24
I have tried using various combinations but I failed. How should I use the parameters to get the same results as in Excel?
采纳的回答
I did not see the .mat file before, although I did look for it.
Try this —
LD = load('timestamp.mat')
format long
timestamp = LD.timestamp
Time24 = datetime(timestamp, ConvertFrom='datenum', Format='MM/dd/yyyy HH:mm:ss.SSS', TimeZone='+02:00')
LastLine24 = Time24(end)
TimeAP = datetime(timestamp, ConvertFrom='datenum', Format='MM/dd/yyyy hh:mm:ss.SSS a', TimeZone='+02:00')
LastLineAP = TimeAP(end)
I prefer 24-hour time. I posted conversions for both here.
I am not certain what sort of resolution you want (or what the data provide). I have them in µs here. Append more ‘S’ characters to get additional displayed precision.
The Format name-value pair determines how the datetime values are displayed. It keeps full internal precision regardless.
EDIT — (29 Jan 2025 at 13:22)
Adeded timestamp.mat file import and changed the datetime calls to accommodate it.
EDIT — (29 Jan 2025 at 14:42)
Corrected (added) time zone offset, changed seconds resolution from 6 to 3 (µs to ms). .
.
7 个评论
Hany Ferdinando
2025-1-29
Hany Ferdinando
2025-1-29
Star Strider
2025-1-29
My pleasure!
I was going by the image, since that appeared to be what you wanted the dates and times to be. My first conversion code returned those results.
I corrected the time zones. You can change the seconds precision by changing the number of ‘S’ characters. I changed them back to three as well here, although in:
I got the following results.
05:37:04.1507
05:37:04.1520
05:37:04.1532
05:37:04.1545
05:37:04.1557
you specified at least four.
.
Hany Ferdinando
2025-1-29
After experiimenting with it a bit, it now seems to be working.
I have no idea what the original problem was wiith it, however changing the TimeZone after creating the datetime array works, when including it as an argument does not (although it should, according to the documentation). Also, the time itself seems to have changed, since the original file had times beginning at 12:00 and this file begins at 05:00.
Try this —
LD = load('timestamp.mat')
format long
timestamp = LD.timestamp
OriginalTime24 = datetime(timestamp, ConvertFrom='datenum', Format='MM/dd/yyyy HH:mm:ss.SSS', TimeZone='Z')
OT24TZ = OriginalTime24.TimeZone
NewTime1 = OriginalTime24;
NT1TZ = NewTime1.TimeZone
TZ = '+02:00';
NewTime1.TimeZone = TZ
NT1TZ = NewTime1.TimeZone
NewTime2 = OriginalTime24;
NT2TZ = NewTime2.TimeZone
TZ = '-07:00';
NewTime2.TimeZone = TZ
NT2TZ = NewTime2.TimeZone
Use the formats for either 24 Hour time or AM/PM time, as you prefer.
To do that —
NewTime1
NewTime1AMPM = NewTime1;
NewTime1AMPM.Format = 'MM/dd/yyyy hh:mm:ss.SSS a'
NewTime2
NewTime2AMPM = NewTime2;
NewTime2AMPM.Format = 'MM/dd/yyyy hh:mm:ss.SSS a'
Success!
.
Hany Ferdinando
2025-1-30
Star Strider
2025-1-30
As always, my pleasure!
The solution was defining the TimeZone of the original as 'Z' (or equivalently, 'UTC'), although I thought that was the default. After that, defining the other time zones is straightforward.
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