Cleveland Motion Controls ULTRA SERIES SLIM CELL TRANSDUCER REV AA - Manual (Page 6)

U LTRA S ERIES S LIM C ELL T RANSDUCER AO-70263 R EV AA
P AGE 6 OF 18
1.4 P
RE
-I
NSTALLATION
P
RECAUTIONS
1.4.1.1 S HIPPING
Shock and vibration transmitted to the transducers by the sensing roll during transportation can damage the
transducers. It is essential that you remove the sensing roll when the machine is shipped with the transducers
mounted.
1.4.1.2 R OLL B ALANCE
The sensing roll should be adequately balanced. Understand that the balance of the sensing roll will be more
demanding than that typically needed in general rotating machinery. The goal goes beyond just limiting the force to
which bearings will be subjected, but rather to minimize the generation of an unintended noise component in the
transducer tension signal. The centrifugal force caused by imbalance can be estimated using the following formula:
F = (1.77 x 10 -6 ) x W x R x (RPM) 2
Where:
F = centrifugal force (in units of lb-f)
W = weight imbalance (in units of ounces)
R = radius of displacement, distance of imbalance weight from roll axis of rotation (in inches)
RPM = Revolution per minute
Note that that the force goes up as the square of the RPM or in other words, doubling the RPM causes four times the
force. Because rolls tend to have a high length-to-diameter ratio, two-plane (dynamic) balancing is recommended.
Balancing is particularly needed where higher RPMs and lower web forces are involved.
To illustrate how much imbalance induced “noise” could be generated, the following table shows the force
disturbance for various ISO balance grades for an illustrative case of a 20 pound roll (4” diameter x 36” long,
aluminum ) rotating at 1500 RPM.
Balance Grade
(ISO 1940/1):
Residual Imbalance:
Resultant Force due to
Residual Imbalance:
G16 1.25 oz-in +/- 5 lb-f at 25 Hz
G6.3 0.5 oz-in +/- 2 lb-f at 25 Hz
G2.5 0.2 oz-in +/- 0.8 lb-f at 25 Hz
G1 0.08 oz-in +/- 0.3 lb-f at 25 Hz
1.4.1.3 C RITICAL R OLL S PEED
Even with a balanced roll, a vibration can be set up in a stationary shaft. If this vibration (in cycles per minute)
occurs at the harmonic frequency of the shaft, the transducers can be damaged. To determine the critical roll speed,
use the following formula:
Critical roll speed in RPM = 4.8 x 106 x Shaft O.D.
(Shaft Length) 2
(Dimensions are in inches)
To assure that this issue is avoided, the critical roll speed should be at least 20% above the roll speed attained at
maximum web speed.
1.4.1.4 A VOIDING D AMAGE TO THE T RANSDUCERS
To avoid damaging the transducers, refrain from repetitive overloading above the maximum working force or severe
overloading.
1.4.1.5 E XCITATION V OLTAGE
Maximum Excitation Voltage for the Ultra Series Slim Cell transducers must be limited to 5.6 VDC or 5.6 VRMS. Do
not use 10 Volt excitation or possible damage to the semiconductor strain gage elements can occur. Before applying
power to the amplifier, verify that the amplifier excitation voltage has been set to 5.0 VDC.