Manual, F/T Sensor, Data Acquisition (DAQ) Systems
Document #9620-05-DAQ.indd-20
Pinnacle Park • 1031 Goodworth Drive • Apex, NC 27539 • Tel: 919.772.0115 • Fax: 919.772.8259 • www.ati-ia.com • Email: info@ati-ia.com
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7.2 Detecting Failures (Diagnostics)
7.2.1 Detecting Connection Issues
The F/T system is designed to output voltages that are within the specied output voltage range
(±5V or ±10V) as long as the transducer is not being overloaded and 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 specied 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, a problem with the transducer or
its cabling may exist.
CAUTION: When any strain gage output is saturated or otherwise inoperable,
all transducer F/T readings are invalid. Therefore, it is vitally important to
monitor for these conditions.
7.2.2 Detecting Cable Problems
A properly functioning DAQ system will deliver voltages representative of transducer loading from
the transducer to the DAQ card inputs. The DAQ system provides two safety features to aid in
detection of cabling problems that could disrupt the reading of transducer voltages.
1. If the cable is disconnected between the transducer and its IFPS or PS box, voltages sent to the
DAQ card from the box will be forced to a saturation level.
2. The T out signal outputs a voltage that is either -1.54V if no temperature reader circuit
is installed, or a voltage greater than +0.5V if the temperature reader is installed and the
temperature is above -10
o
C.
If the acquired transducer voltages are A/D saturated or T out is not between -1.6V to -1.5V, or not
between +0.5V and saturation, there may be a cable issue.
7.2.3 Detecting Sensitivity Changes
Sensitivity checking of the transducer can be used to measure the transducer system’s health. This
is 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:
1. If the end-effector has moving parts, they must be moved in a known position.
2. Place the robot arm in an orientation that allows the gravity load from the end-effector to exert
load on any transducer output axes.
3. Record the output readings.
4. Position the robot arm to apply another load, this time causing the outputs to move far from the
earlier readings.
5. Record the second set of output readings.
6. Find the differences from the rst 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).
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