Cleveland Motion Controls DIN Rail Amplifier MWI-13262 Ultra Series Non-Isolated REV BA - Manual (Page 21)

MAN-13262 R EV BA DIN R AIL A MPLIFIER , MWI-13262 U LTRA
3.4 A PPLYING F ORCE TO T RANSDUCERS
The application of an accurate calibration force can be a challenge. Keep the following points in mind:
• The test force should be a moderate percentage of the intended working force of the
transducer, and never over the 100% Mean Working Force (MWF) or you may risk
calibrating with an overloaded (“clipped”) transducer signal.
• Allow the transducer and amplifier to reach thermal equilibrium before conducting
calibration. Ideally, the temperature should reflect the expected operating conditions.
• 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 ).
• Always apply and remove the test load in a continuously increasing or decreasing manner, so
that the force changes are monotonic. This helps to avoid disturbing any hysteresis
component of the transducers force signal.
• Keep in mind that passing a cord over a roll on its way to the transducer will inevitably
cause some amount of friction. The worst case scenario is in passing the working part of a
cord over a roll that doesn’t readily freewheel. A test was conducted to determine the loss on
a stationary 4” diameter anodized roll with a 90 degree wrap angle. It exhibited a 25 to 30%
loss in force due to friction!
• With very low force transducers, consider that connecting a test mass will involve some
finite cord mass.
• When calibrating for a particularly wide roll that will always have a narrower product
tracking to one side, consider applying the calibration force at the roll position that
represents the center of the product. This will automatically cancel some of the affects of
transducer gain imbalance without the need to actually re-balance the transducers gains
within the amplifier.
• It is a good practice to verify linear operation of the transducer and amplifier by applying a
final test force that falls somewhere between the zero and full-scale endpoints. The intent is
not to conduct any calibration per se, but to confirm the hardware’s ability to accurately
report a measured force.
3.5 A DJUSTMENT T OOLS
Using the correct tools simplifies the setup process and necessary adjustments. Keep the following points in mind:
• The Ultra Series DIN Rail amplifier utilizes two different potentiometer styles. The Gain
and Zero adjustments located on the front of the amplifier are more likely to be adjusted over
the life of the product. For that reason they are physically larger and more robust. The
industry standard “pot tweaker” is an ideal tool. The adjustment tool should have dimension
on the order of 0.5mm (.020 inches) blade thickness and be 2.5 mm wide (0.1inches).
• The adjustments that are usually made only once during initial setup are located behind a
snap on access cover. This less obvious location helps to discourage alteration by
unqualified persons. The infrequent adjustment of these potentiometers has warranted the
use of smaller surface mount technology devices (SMT). A correspondingly narrower blade
is needed (1.4 mm wide, 0.055”inches).
• When changing the internal jumper-switch settings, it is always advisable to change the
settings with the 24 VDC power removed. If this is not possible, it becomes particularly
important to use a non-conductive tool to alter switch positions. Be sure that jumper-switch
settings are fully positioned, to avoid accidentally putting it in an “in-between” state.
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