TorqueTrak Revolution Common Topics

A) FEATURES & BENEFITS

The TorqueTrak Revolution system provides continuous Torque, Power, RPM and Direction of Rotation output data from the shaft of your rotating machinery. 14-bit digital signal processing ensures precise and reliable 4-20mA analog output data signals. Setup tools make calibration and scaling easy. The system uses non-contact inductive power and data transfer for maintenance-free, continuous operation without batteries or wear surfaces. The TorqueTrak Revolution is easy to install. Typically, no modifications to the machine or shaft are required.

B) HOW IT WORKS

The TorqueTrak Revolution transfers power and data inductively between the stationary and rotating components. The nominal air gap between the stationary Power Coil and Rotating Collar is 0.2+/-0.1 inches (5+/-3mm), so alignment is not critical. An alternating current with a frequency of 460kHz energizes the Power Coil that induces a current in the coil attached to the Rotating Collar. The alternating current generated on the rotating half is rectified and filtered to energize the rotating transmitter as well as the strain gage. Digital data is sent back to the stationary half by modulating the power draw of the transmitter circuit at a lower frequency. The modulated power is detected and demodulated by the Master Control Unit as digital data that is finally delivered as a 4-20mA analog current output signal. Combining this torque data with data collected by the Hall effect sensor at the base of the Power Coil that detects magnets embedded in the Rotating Collar, the TorqueTrak Revolution provides the other three data signals: Power, RPM and Direction of Rotation.

C) SYSTEM INSTALLATION

The TorqueTrak Revolution installs easily to almost any shaft from 1 inch (25mm) up to 40 inches (1,016mm). At the time of order, the user will specify the exact shaft dimension. The Rotating Collar is machined to fit precisely to the shaft outer diameter. Care should be taken when attaching the Rotating Collar to the shaft to not over-tighten the bolts. This can cause damage to the coil boards and connectors. The user will also need to provide an adjustable mounting bracket to hold the Master Control Unit (MCU) in the proper location near the shaft. Alignment of the Rotating Collar and MCU is important for proper function. Due to vibration or other factors, extra bracing may be required to support the stationary Power Coil attached to the MCU. Refer to Appendix E in User Manual available on this website for exact mounting dimensions. The user can use any combination of the four output signals for any purpose: monitoring, process control, or as an alarm trigger. Signal wires should be between 28-14 AWG and shielded to prevent noise. Consideration should be given to data processing, including storage and display. We recommend DATAQ (www.dataq.com) and National Instruments (www.ni.com) data acquisition products. The maximum load resistance of each of the current output signals is 500 ohms. Power also needs to be supplied to the Master Control Unit. The user specifies the preferred power supply at the time of order: 12VDC (0.5-2A), 110VAC (250-500mA) or 220VAC (125-250mA). Wire carrying the power should be 22-10 AWG. It is recommended that power is supplied from a dedicated source such as a UPS. There should be no surrounding metal within 1 inch (25mm) of the Power Coil (more clearance is recommended for systems on shafts greater than 14"). Nearby metal can draw energy away from the system, degrading the inductive link. If too much energy is lost, it can prevent the system from functioning properly. The estimated installation time is four hours (not including bracket preparation and strain gage installation).

D) STRAIN GAGE INSTALLATION

Installation of the strain gage is often the most intimidating step in the process. After a little practice, it is a skill that can be quickly mastered. Refer to the step-by-step procedure in the User Manual for a standard full-bridge torque-pattern strain gage, Vishay Micromeasurements Group Part #: CEA-06-250US-350, using the Strain Gage Application Kit, Vishay Part #: GAK-2-200. Strain gages and application kits can be ordered through Binsfeld Engineering Inc. Once the gage has been applied, simply solder the ribbon cable from the Rotating Assembly to the strain gage as illustrated in the manual. The strain gage can now be preserved by using a protective polymer coating, Part #: M-Coat J, also available from Vishay. For more information on the strain gage products manufactured by Vishay, refer to their website: www.vishay.com.

E) TORQUE OUTPUT SIGNAL

Torque is linearly proportional to mechanical strain sensed by the strain gage. This strain creates a change in resistance within the strain gage measured by the transmitter in the Rotating Collar of the TorqueTrak Revolution. The Torque Output Signal is a 4-20mA signal proportional to the actual torque experienced by the shaft and can be scaled from 0.25 to 4 times the Full Scale Torque value. The factory setting for Torque is 12+/-8mA, meaning zero torque is 12mA after the initial gage offset adjustment, 20mA is positive Full Scale Torque in one direction, and 4mA is negative Full Scale Torque in the other. If torque is only of interest in one direction, at the flip of a switch the system can be configured to display zero torque as 4mA and positive Full Scale Torque as 20mA in order to utilize the full signal span.

F) POWER OUTPUT SIGNAL

Mechanical power is calculated using the Torque and RPM values measured by the TorqueTrak Revolution. The 4-20mA Power Output Signal is proportional to actual power on the shaft and scaled by the user. The factory setting for Power is 12+/-8mA, meaning zero power is 12mA, 20mA is the power generated at positive Full Scale Torque in one direction, and 4mA is the power at negative Full Scale Torque in the other direction. If power is only of interest in one direction, at the flip of a switch the system can be configured to display zero power as 4mA and positive Full Scale Power as 20mA in order to utilize the full signal span.

G) RPM OUTPUT SIGNAL

The Rotating Collar of the TorqueTrak Revolution contains six evenly spaced magnets that pass by a Hall effect sensor in the Master Control Unit. The sensor "pulses" are output as a current pulse or frequency signal. The pulse is either normally 5mA pulsing to 19mA or vice versa depending upon the direction of shaft rotation. For example, a 10Hz RPM Output Signal would indicate 100 RPM shaft speed. Optional Accessory: Frequency-to-Current Converter & RPM Display from IFM Efector, Model: FR-1 Series Speed Monitor, Part #: DD2003. This module converts the RPM frequency signal to a 4-20mA analog current signal and displays the actual RPM. Refer to their website for more information: ifmefector.com

H) DIRECTION OUTPUT SIGNAL

The TorqueTrak Revolution provides a simple binary signal to indicate direction of shaft rotation: 5mA in one direction and 19mA in the other.

I) ACCURACY & CALIBRATION

The TorqueTrak Revolution can provide accuracy within +/-1% of Full Scale. Accuracy is a function of two primary elements: proper installation of the strain gage and the "sensitivity" of the system. The "system" includes the shaft, strain gage, and the TorqueTrak Revolution system. Sensitivity is expressed in terms of Torque Input per Current Output. This Input-Output relationship is linear throughout the elastic range of the material. The most precise method for determining the sensitivity is performing a true mechanical calibration, often referred to as a deadweight calibration. With this method, a known torque is applied to the shaft (i.e., a known force or weight is applied to the shaft at a known distance from the load to the center of the shaft). Example: A 100-pound load on a 1-foot moment arm creating 100 foot-pounds of torque is applied to the shaft. Observe the change in the Torque Output Signal. The sensitivity of the system is equal to this Torque Input to Current Output ratio. Changing the amount of mass or length of the moment arm can be useful to confirm the sensitivity and linearity of the system. Be careful when using free weights: the perpendicular distance from the load to the shaft will be slightly less once the weight is applied depending on how much the shaft twists. The other, more commonly used, method is by calculation of the Full Scale Torque. Taking the values for Shaft Diameter (this should be accurately measured), Modulus of Elasticity and Poisson Ratio of the shaft material (these can be estimated if unknown but may introduce an uncertaintanty of as much as +/-3%), and the Gage Factor of the strain gages being used (printed on the package), then the Full Scale Torque result for a given range of strain can be determined. There are two ways to calculate the Full Scale Torque. One is by using the equation in Appendix B of the User Manual, and the other is to use the Torque Range Calculator in the Tech Info section of this website. For the Revolution, the result of this calculation is the Full Scale Torque at 4 or 20mA (- or +). The sensitivity is this calculated value for Full Scale Torque Input divided by the Full Scale Current Output (8 or 16mA with Torque Dipswitch #3 applied; refer to the User Manual). The online calculator also provides a convenient method for determining the "RPM Factor" switch setting in the Master Control Unit. This factor relates Power to Torque and is user-configurable. Refer to the User Manual available on this website for more information.

J) SHUNT CALIBRATION SWITCH

This is a useful tool for confirming setup of the TorqueTrak Revolution and when setting the Gain. When enabled, the Shunt Calibration Switch applies a precision resistor in parallel with one arm of the strain gage, simulating a strain equal to 50% of the Full Scale Torque. The Shunt Calibration Switch can be used any time to verify system calibration.

K) LOW PASS FILTER

In some applications, the full 1,000Hz frequency response of the torque and power data signals is not required or desired. The Torque and Power output signals can be filtered to effectively "smooth out" the data. The Low Pass Filters are selectable by means of dipswitches inside the Master Control Unit. The following filter options are available: 12, 1.5 and 0.1Hz.