Cleveland Motion Controls DIN Rail Amplifier MWI-13261 Ultra Series Isolated REV BA - Manual (Page 22)

DIN R AIL A MPLIFIER , MWI-13261 U LTRA S ERIES MAN-13261 U LTRA R EV BA
3.3.1 S AFETY C ONSIDERATIONS
Don’t let safety be an afterthought. Before beginning calibration of transducers, review and follow applicable
policies and procedures to ensure worker safety. Machinery must be in a safe state, and you should be aware of
additional hazards that can arise when calibrating higher force transducers. The following points are important to
remember:
• When dead weights are used to produce a force, always wear steel-toed shoes.
• When manually handling weights, use safe lifting practices to avoid injury.
• Size any cordage or straps with an ample safety factor to reduce the chances of failure
and falling weights.
• Consider where the cords and weights will travel should a failure occur.
• Check that all hardware is mounted with the appropriate fasteners (thread size and pitch,
fastener grade, length of thread engagement).
3.3.2 C HECKING T RANSDUCER M OUNTING
Before preparing to apply force to the transducer(s) and calibrating the amplifier you should check to be sure that the
load cell is orientated and mounted in accordance to the transducer installation instructions. Common problems
include:
• Failure to orient the transducer on a flat (machined) surface.
• Poor shaft alignment that exceeds allowable limits.
• Excessive or insufficient fastener torque.
• The transducer is not mounted correctly and the axis-sensing is not true to the applied
force (bi-sector of the wrap-angle).
• The roll shafts are mounted without allowance for shaft expansion or contraction.
• The transducer is positioned in the web path so that the wrap angle is not constant.
For more information about proper practices for applying calibration, refer to section 3.5 in this document.
3.4 A CCURACY C ONSIDERATIONS
The application of an accurate calibration force requires careful attention to minimizing the non-ideal affects of the
real world. Keep the following points in mind:
• Allow the transducer and amplifier to reach thermal equilibrium before conducting
calibration. Ideally, the temperature should reflect the expected operating conditions.
• The test force should be a moderate percentage of the intended working force of the
transducer, and never over the 100% Maximum Working Force (MWF) or, you risk
calibrating with an overloaded (“clipped”) transducer signal.
• Cycle the load on the transducer a number of times with the test force to pre-condition or
“set” the transducer prior to calibration. Repeat this procedure again before calibrating if
the transducer has been disturbed (i.e. bolts re-torqued).
• With very low force transducers consider that connecting a test mass involves some finite
cord mass.
• Passing a cord over a roll on its way to the transducer inevitably causes some amount of
friction. The worst case scenario involves passing the working part of a cord over a roll
that doesn’t readily freewheel.
• When all else is done correctly, the largest remaining contributor to error is friction. If
friction cannot be reduced, consider determining the magnitude of the friction through
measurement and then making first order corrections numerically.
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