Data acquisition time of ocean optics spectrometer

Hi, LVers,
I has a S2000 multichannel fiber optic spectroscopy system. It includes two channels, master and slave. Additionally there is a channel labeled as 'LS-1'. I use labview and driver OOILVD32.dll to control this spectroscopy. In OOILVD32.dll, I use vi 'OOI SCAN' to acquire spectral data through master channel.
In vi "OOI SCAN", I disable all slave channels (there are 7 slave channels) and enable master channel only. However, I find that the data acquisition time is always approximately two times of the "sampling frequency" we set. E.g. for sampling frequency of 75 ms (a small value), the spectral data acquisition time is approx. 160-170 ms; for a sample frequency of 4000 ms (a large value), the spectral data acquisition time is approx. 8300-8400 ms, so on and so forth.
I am very confused with this phenomenon. I guess the most probable reason is that both master and slave channels are always enabled even one of them is software disabled. Because this product is discontinued, I can not find the manual. Anybody could advise me how this such a spectrometer works internally? Is there any multiplexing acquisitions inside?
Thanks in advance.

Hi Hello183,
Unfortunately, I do not know how your specific device works, however, I did find the product page for this device on the Ocean Optics web site, which points to the USB4000-series Plug-and-Play Spectrometer for more details. There seems to be a operations manual for this device. Perhaps this can shine some light on how the sampling works for your device as well.
Aaron P
National Instruments
Applications Engineer
http://www.ni.com/support

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Attachments:
Datalog1 71805.vi ‏1252 KB

Hi,
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First of all, thanks a lot guys for having answered me.
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I'm waiting for your suggestions...
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Attachments:
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mesure example.xls ‏9 KB
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new_control_and_acquisition_program.vi ‏946 KB

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http://help.sap.com/saphelp_nw04s/helpdata/en/52/777e403566c65de10000000a155106/content.htm
https://www.sdn.sap.com/irj/sdn/webinar?rid=/library/uuid/230d95df-0801-0010-4abb-ace1b3d197fd
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