Automated Test Weight Lifter for "MD" Style Weigh Belts
 More and more weigh feeders are being used in conjunction with statistical
process control where performance records are routinely generated
and recorded as required by a customer's quality assurance program. Such
a record should contain a "validation of scale calibration" step to be truly
meaningful as a quality assurance tool. Thayer Scale's Automated Test
Weight Lifter ("ATWL") provides a means for automatically applying a
known test weight and going through a calibration sequence on computer
or push-button demand to check scale calibration. A "foolproof" self checking
software algorithm in the feeder control instrumentation prevents
erroneous calibration.
CALIBRATION is fast, accurate and reliable
Thayer Scale's test weight calibration method has proven accurate and reliable
over decades of in-plant use. Unlike material sampling, it is always
clean, fast and safe. Unlike electronic signal simulation, it actually tests
the performance of critical electro-mechanical components under the full
deflection range of the load cell. Adding the THAYER Automated Test
Weight Lifter now makes calibration even easier and more exact.
Other Methods of Calibration :
Electronic Signal Simulation: Fast, but does not apply load to scale.
Test Chain: Difficult to use, storage can be a problem, time consuming,
susceptible to wear, prone to accidents.
Material Test: Most comprehensive, but very time consuming. Accuracy
of calibration is subject to accuracy of sampling method and accuracy of
scale used to weigh samples.
A simple, rugged mechanism holds the test weight above the scale platform during normal feeder operation. Upon demand
from the THAYER instrument, the mechanism lowers the test weight from the storage position onto the scale platform via a
pneumatic air cylinder. For operator supervised calibration, the operator only touches the YES/NO pushbuttons on the instrument,
which can be placed in a remote location. For automatic calibration, the THAYER instrumentation is linked to a host
computer or PLC, thereby eliminating the need for operator involvement.
Error findings are automatically logged into the instrument memory and can be retrieved by the operator at anytime, to review
past calibration results.
Any improper conditions that could invalidate calibration results is detected by the instrument, which halts calibration and
delivers an alarm massage and diagnosis of the problem to the operator. Calibration has never been faster, easier or more
reliable.
ATWL Benefits:
- Self-storing Test Load can not be misplaced
- Minimizes downtime for calibration checks
- Eliminates risk of injury to personnel
- Assures that correct test load is always applied
- Precisely controls positioning of test load on scale
- Permits full calibration from remote location
- Permits verification of active measurement range
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