Metrix HI 803 - Recommended Maximum Loads to be Placed on the TTS; Types of Sensors

Doc# 0296-0018 • REV R (July 2017) Page 42 of 61
CAUTION: THE FLEXURE SYSTEMS IN THE VIBRATOR ARE SUSCEPTIBLE TO DAMAGE DUE TO TWISTING
FORCES APPLIED TO THE SHAKER HEAD.
WARNING: DO NOT OVERLOAD THE INSTRUMENT FOR EXTENDED PERIODS OF TIME AT HIGH AMPLI-
TUDES. TO DO SO MAY CAUSE PROPERTY DAM AGE.
Displacement Limits - As long as the displacement limits of the vibrator are not exceeded, the full power
of the amplier can be used to drive the shaker. If the TTS is being used to test a large load, the ampli-
tude limit may not be reached. The following limits apply:
• The maximum displacement at 10 Hz is 0.1 inches p- p.
• The maximum velocity at 29.3 Hz is 10 inches/second peak.
• The maximum acceleraon at 61.73 Hz is 10 G peak.
Recommended Maximum Loads to be Placed on the TTS
FREQ, RANGE
0-100
GRAMS
100-250
GRAMS
250-500
GRAMS
500-750
GRAMS
10-100 Hz 10g 4g 2g 1g
100-1000 Hz 7g 4g 2g 1g
1-2 kHz 3g 1.5g 1g n/a
1-10 kHz 3g 1.5g n/a n/a
TABLE 5-2: MAXIMUM LOADS TO BE PLACED ON THE TTS
NOTE: If tesng includes higher frequencies (5 kHz to 10 kHz), special care must be taken when install-
ing the test transducer on the shaker head (Also known as the Reference Accelerometer). Before stud
mounng the accelerometer, a coupling uid (thin coat of Vacuum Grease or Machine Oil) should be
applied to the mang surfaces. The cou- pling uid opmizes the frequency response by increasing
the mechanical coupling sness, in addion to providing lubricaon. Failure to use the coupling uid
will result in increased variances proporonal to increasing frequencies.
Stud Torque Values - Use a torque wrench and torque the studs to the following values:
• 1/4-28 Threads 26 inch-pounds nominal
• 10-32 Threads 20 inch-pounds nominal
CAUTION ALWAYS USE THE SPANNER WRENCH WHEN TORQUING AGAINST THE SHAKER HEAD TO
PREVENT DAMAGING THE SUSPENSION SYS- TEM THAT SUPPORTS THE MOVING ELEMENT AND THE
SHAKER HEAD.
Types of Sensors The three principal vibraon sensor or monitor types are:
• Displacement - Eddy current Device
• Velocity - Spring held magnet moving a coil of wire
• Accelerometer - piezoelectric device similar to ultra- sonic transducers.
Displacement Sensor
Displacement sensors are non-contact devices used to measure the gap between the plant
equipment and the xed sensor. The sensor measures vibraon as horizontal or vercal
moon. Best for measuring low frequencies. The coil in the eddy current device