F/T DAQ Installation and Operation Manual
Document #9610-05-1017-06
ATI Industrial Automation, 1031 Goodworth Drive, Apex, NC 27539 USA +1-919-772-0115 www.ati-ia.com
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6. Advanced Topics
6.1 Data Collection Rates
Our DAQ F/T sensor systems are designed to be electrically compatible with most
commercially available general-purpose and high-accuracy data acquisition hardware. For
best performance in all applications, the transducer electronics do not filter the outputs. This
allows collection of all transducer frequency content. Please note that to satisfy the Nyquist
Theorem
†
, the data needs to be coupled at a rate that is greater than twice the highest
frequency present, even if you are not interested in data at that frequency.
Please note that significant error can be introduced in the transducer data if a National
Instruments E-Series card is sampling each data set at over 40 kHz (240 kHz per channel).
Users with fast NI-DAQ devices should not use the single-scan functions of NI-DAQ, such
as AI_Read_Scan and AI-VRead_Scan. A buffered operation (such as Scan_Op) should be
used instead. In the demo, ATI DAQ FT Demo, the Buffer Mode option should be enabled.
†
The Nyquist Theorem applies to data collection and states that data acquired must be collected at a data rate
greater than twice the highest frequency present in the data, otherwise the data will be erroneous. The theorem was
developed by Henry Nyquist as he sought to improve communications systems in the first part of the twentieth
century.
6.2 Detecting Failures (Diagnostics)
The F/T system is designed to output voltages that are within the specified output voltage
range (+
5V or +10V) as long as the transducer is not being overloaded and the transducer is
connected to the PS or IFPS box. If the transducer cable is disconnected or has been
damaged, the output of the system will be outside the specified output voltage range. By
performing periodic checks of the voltages, a failure can be detected. If any of the voltages
are at or outside this range, there may be a problem with the transducer or its cabling.
Sensitivity checking of the transducer can also be used to measure the transducer system’s
health. This can be done by applying known loads to the transducer and verifying the system
output matches the known loads. For example, a transducer mounted to a robot arm may have
an end-effector attached to it. If the end-effector has moving parts, they must be moved in a
known position. Place the robot arm in an orientation that allows the gravity load from the
end-effector to exert load on many transducer output axes. Record the output readings.
Position the robot arm to apply another load, this time causing the outputs to move far from
the earlier readings. Record the second set of output readings. Find the differences from the
first and second set of readings and use it as your sensitivity value. Even if the values vary
somewhat from sample set to sample set, they can be used to detect gross errors. Either the
resolved outputs or the raw transducer voltages may be used (the same must be used for all
steps of this process).
6.3 Scheduled Maintenance
For most applications there are no parts that need to be replaced during normal operation.
With industrial-type applications that continuously or frequently move the system’s cabling
you should periodically check the cable jacket for signs of wear. These applications should
implement the procedures discussed in Section 6.2—Detecting Failures (Diagnostics) to
detect any failures.
The transducer must be kept free of excessive dust, debris, or moisture. Applications with
metallic debris (i.e., electrically-conductive) must protect the transducer from this debris.
Transducers without specific factory-installed protection are to be considered unprotected.
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