Omega OMB-DAQBOARD-3000 Manuel D’Utilisation
5-10 Counter Input Modes
918494
DaqBoard/3000 Series User’s Manual
Upper 16-bits of the 32-bit counter
Lower 16-bits of the 32-bit counter
Range (Hz)
Ticksize (nS)
Averaging
Option
Range (Hz)
Ticksize (nS)
Averaging
Option
15u – 1500u
20833.333
1
1 – 100
20833.333
1
150u – 15m
2083.333
1
10 – 1k
2083.333
1
1500u – 150m
208.333
1
100 – 10k
208.333
1
15m – 1500m
20.833
1
1k – 100k
20.833
1
150m – 15
20.833
10
10k – 1M
20.833
10
1500m – 150
20.833
100
100k – 5M
20.833
100
15 – 1500
20.833
1000
1M – 5M
20.833
1000
Frequency Ranges for a 16-bit value, sampling error is less than 0.21%
Each frequency range given in the previous table-set can be exceded. If the input waveform goes under-
range by too much, the counter value will top out at 65535 indicating you have reached the lowest possible
frequency that can be measured on that range. If the input waveform goes over range by too much, the
counter will return values that are very course and have a lot of sampling error. The values returned will
have a small number of counts for the period duration. If an input waveform cannot fit within one of the
16-bit ranges shown above or requires much higher accuracy, then a 32-bit range should be considered.
range by too much, the counter value will top out at 65535 indicating you have reached the lowest possible
frequency that can be measured on that range. If the input waveform goes over range by too much, the
counter will return values that are very course and have a lot of sampling error. The values returned will
have a small number of counts for the period duration. If an input waveform cannot fit within one of the
16-bit ranges shown above or requires much higher accuracy, then a 32-bit range should be considered.
Full 32-bit Counter
Range (Hz)
Range (Hz)
Ticksize (nS)
Averaging Option
15u – 100
20833.333
1
150u – 1k
2083.333
1
1.5m – 10k
208.333
1
15m – 100k
20.833
1
150m – 1M
20.833
10
1.5 – 5M
20.833
100
15 – 5M
20.833
1000
Frequency Ranges for a 32-bit Value,
Sampling Error is Less than 0.21%
The 32-bit ranges shown above are much wider than the 16-bit ranges, but also require the full 32-bit value
to be returned. Since digital or counter channels do not take up any time in the scan period there is no
disadvantage in reading a 32-bit counter versus a 16-bit counter. The 32-bit frequency ranges can also be
exceeded with a loss of accuracy or topping out at 4,294,967,295 counts.
to be returned. Since digital or counter channels do not take up any time in the scan period there is no
disadvantage in reading a 32-bit counter versus a 16-bit counter. The 32-bit frequency ranges can also be
exceeded with a loss of accuracy or topping out at 4,294,967,295 counts.
Some measurements will require the accuracy of an input waveform to be free of sampling error, having only
the absolute accuracy of the internal timebase as the source of error. Sampling error can be averaged out to
give the required result. In most cases, the 3000 Series board can perform the required averaging on the
values before they are returned to the PC. The frequency ranges shown below will give a sampling error
that is less than 10ppm or 1ppm.
the absolute accuracy of the internal timebase as the source of error. Sampling error can be averaged out to
give the required result. In most cases, the 3000 Series board can perform the required averaging on the
values before they are returned to the PC. The frequency ranges shown below will give a sampling error
that is less than 10ppm or 1ppm.
Full 32-bit Counter
<10 ppm
Full 32-bit Counter
<1 ppm
Range (Hz)
Ticksize (nS)
Averaging
Option
Range (Hz)
Ticksize (nS)
Averaging
Option
15u – 500m
20833.333
1
15u – 50m
20833.333
1
150u – 5
2083.333
1
150u – 500m
2083.333
1
1.5m – 50
208.333
1
1.5m – 5
208.333
1
15m – 500
20.833
1
15m – 50
20.833
1
150m – 5k
20.833
10
150m – 500
20.833
10
1.5 – 50k
20.833
100
1.5 – 5k
20.833
100
15 – 500k
20.833
1000
15 – 50k
20.833
1000
High Accuracy Frequency Ranges for a 32-bit Value
that has little sampling error (<10ppm, <1ppm)
If the input frequency is required to have less than 1 ppm sampling error and is greater than 50kHz, use the
15– 50kHz, 1ppm range. The values returned will have sampling error that is greater than 1ppm but they
can be averaged by the PC software to further reduce the sampling error.
15– 50kHz, 1ppm range. The values returned will have sampling error that is greater than 1ppm but they
can be averaged by the PC software to further reduce the sampling error.