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In datasheet for Keithley 3706A it is written that sampling time can be defined between 10 microseconds and 250 miliseconds.
I am using Keithley 3706A and 3730 Matrix Card.
The problem is when I perform 100 measurements with 0,1 s of sampling time on single channel (3730 Matrix card) my total measuring time is 9,905572891 seconds.
Error[%] = ((Real_time – Ideal_time) /Ideal_time)*100
Error = ((9,905572891 – 9,9)/9,9)*100 = 0,0563%
On the other hand when I perform 100 measurements with 0,2 ms of sampling time on single channel (3730 Matrix card) my total measuring time is 0,025583506 seconds.
Error = ((0,025583506 – 0,02)/0,02)*100 = 28%
As You can see error is really big.
I would like to know how can avoid the delays when sampling time is shorter?
Please find attached Lua code.
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Even with delays and autozero turned off, there is still some overhead.
Using your code with the 200usec aperture and printing out all the timestamps from the 100 readings, a delta on the time stamps shows an average delta time of 256usec vs. your desired 200usec of delta time.
Code: Select all
for i = 1, reading_buffer.n do print(reading_buffer.relativetimestamps[i]) end -- for loop
At 100 measurements, this accounts for the extra 5.6msec in your final timestamp ( 0,025583506 vs. ideal 0,020000)
If the 200usec sampling interval is important, you will need to set the dmm.aperture = (desired interval - overhead).
Keep in mind, the timestamp accuracy is 100usec.
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