FAQ: Torque and Power Measurement System (TPMS)
How do you attach the encoder belt to the shaft?
The encoder belt can be installed using epoxy adhesives or using micro spot welds. The epoxy adhesive can be standard, Mil-Spec, High temperature, etc.
What is the sampling rate of the TPMS?
The default sampling rate is 500Hz, that provides 0-250Hz frequency range. Using high-resolution encoder belt, the sampling rate can be increased up to 1KHz.
Can the TPMS measure torsional vibration and/or torsional transients?
Yes, the high sampling rate (1kHz) of the TPMS allows it to capture torsional vibrations and sudden torsional transients.
The TPMS can be used to measure the following:
Angular deformation [rad]
Angular velocity [rad/s], Shaft speed [RPM]
Torque [Nm]
Power [W]
How long does it take to install an encoder belt on a 12in diameter shaft?
With adequate preparation, the encoder belt can be installed less than one hour.
What is the depth of the heat affected zone of the microspot welds?
The maximum depth is 0.004 inch (0.1 mm). This is comparable to normal manufacturing tolerances and shaft surface imperfections.
How does the TPMS measure mechanical power?
TPMS measures instantaneous angular deformation ϑ(t) between two locations of the shaft. Using the following formula, the instantaneous torque Τ(t) can be calculated.
Τ(t) = ϑ(t) J G / L
Where:
Τ(t):
ϑ(t):
J:
G:
L:
Instantaneous torque [Nm]
Instantaneous angular deformation [rad]
Polar Moment of Inertia [m^4]
Shear modulus [Pa]
Distance between the two measured locations [m]
The TPMS also measures instantaneous angular velocity ω(t).
The instantaneous angular velocity ω(t) multiplied by the instantaneous torque results the instantaneous mechanical power P(t).
P(t) = ω(t) Τ(t)
Where:
P(t):
T(t):
ω(t):
Instantaneous mechanical power [Watt]
Instantaneous torque [Nm]
Instantaneous angular velocity [rad/s]
What is the angular resolution of the TPMS?
The angular resolution is affected by the following parameters: the pitch of the encoder belt, shaft diameter, sample update rate, and the nominal speed of the shaft.
Test Setup 1:
Using 0.2 inch pitch belt on a 4in diameter shaft that has 1250RPM the noise floor is 5E-6[deg] (5 micro-degree).
Test Setup 2:
Using 0.25 inch pitch belt, 12in diameter shaft that has 3600RPM the noise floor is 0.5E-6[deg] (0.5 micro-degree).
What is the optimum air gap size between the TPMS sensor and the measured shaft?
Generally, the recommended air gap size of 40-200 mils (1 to 5mm).
What is the temperature range of the TPMS sensor?
The TPMS’s default operating temperature is -55°C to 120°C (-67°F to 250°F).
The optional high-temperature version can handle the temperature range of -73°C to +230°C (-100°F to +450°F).
How often do you need to calibrate/recalibrate the TPMS?
The TPMS does not need calibration, all engineering units can be calculated using simple engineering formulas prior installation. One of the advantages of the TPMS is that it measures time instead of resistance such as strain gauge based systems. The resistance of strain gauge is greatly affected by temperature, gauge orientations, installation, etc. Strain gauge systems drift over time and loose accuracy. The TPMS does not need maintenance and it will provide the exact same accuracy after decades of operation.
Can the TPMS installed in a hazardous location?
Yes, the TPMS has sensors that are used where explosion-proof or intrinsically safe sensors are required.
Ratings: Class I, Groups A, B, C, D; Class II Groups E, F, G; Class III.
What is the thickness of the encoder belt?
The encoder belt has 0.007in (0.1778mm) thickness.
What is the maximum width of the encoder belt?
The standard width range of the encoder belt is 1-3 inch (25mm-75mm).
What is the weight of the encoder belt?
The standard width, 1m long belt is about 12 grams.
We have a small diameter shaft. Instead of encoder belts can we use encoder disks?
Yes, the TPMS sensor can target encoder disks.
For small diameter shafts, we suggest using clamp-on encoder disks.
Where is the TPMS made?
It is made in the USA.