Measurement Computing CIO-DAS-TEMP - Manual (Page 12)

Generally, the choice of gate time is a matter of factoring the desired resolution against the time the
actual measurement takes.
Multiple Channels:
When scanning over multiple channels, the software must explicitly select the next channel in the scan
and start a new conversion. Once the next channel is selected, enough time must be allowed for the new
channel’s current to propagate through the multiplexers and Current-to-Voltage Converter to settle at the
Voltage-to-Frequency converter input. T his is most easily done by doing an extra, or ‘dummy’
conversion, waiting for it to complete and then starting the ‘real’ conversion. Thus, if a gate time of
0.0166 seconds is chosen, the maximum scan rate will be:
Scan Rate = 1 / 2 x [gate time]
= 1 / 2 x [0.0166 seconds]
= 30 samples per second
The following table can be used to select the Gate Count based on either desired maximum sampling rate
or desired resolution.
400Hz 0.1 °C 0.0025 sec 5,000 200 samples / sec
50Hz 0.0125 °C 0.02 sec 40,000 25 samples / sec
60Hz 0.015 °C 0.01 sec 33,333 30 samples / sec
Line Frequency
Rejection
Resolution Gate Time Gate Count
Required
Desire Max Sample
Rate
8