Data Translation DT9871, Руководство пользователя

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Principles of Operation
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Optionally, you can return your instrument to Data Translation for recalibration. For
information on factory recalibration, contact Data Translation at 508-946-5100 (if you are in the
USA) or call your local distributor (if you are located outside the USA); see our web site
(www.mccdaq.com) for the name and telephone number of your nearest distributor.
In addition, each instrument auto-calibrates on each power-up cycle to guarantee
high-accuracy measurements. This process, also known as auto-zeroing, resets the zero point
of each A/D. You can also auto-calibrate the instrument at any time (as long as acquisition is
not in progress) using a software command. Refer to your software documentation for more
information on the auto-calibration feature.
Sample Clock Source
TEMPpoint, VOLTpoint, and MEASURpoint instruments support an internal clock with a
maximum sampling rate of 10 Samples/s.
Use software to specify an internal clock source and a clock frequency between
0.000152590219 Hz and 10.0 Hz.
Note: The clock frequency that you specify is rounded to the closest "correct" value that the
instrument can accept without error. Internally, the 10 Hz clock is divided by an integer in the
range of 1 to 65535 (the internal clock divider) to determine the closest value. Using software,
you can query this setting to determine the actual clock frequency that is used.
When the continuous operation is started, all the channels specified in the channel list are read
simultaneously at the specified clock frequency.
Trigger Source
A trigger is an event that occurs based on a specified set of conditions. Acquisition starts when
the instrument detects the initial trigger event and stops when you stop the operation.
TEMPpoint, VOLTpoint, and MEASURpoint instruments support the following trigger
sources for starting analog input operations:
• Software trigger – A software trigger event occurs when you start the analog input
operation (the computer issues a write to the instrument to begin conversions).
• External digital trigger – An external digital trigger event occurs when the instrument
detects a voltage from +3 V to +28 V DC on digital input line 0. Initially, the external signal
must be low and then go high for at least 100 ms to be detected as a trigger. Once
triggered, the state of digital input 0 is ignored.