Strain Gage Reaction Torquemeters Installation Guide
S. Himmelstein and Company
© 2017 S. Himmelstein and Company—all rights reserved www.himmelstein.com
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I. Introduction
Himmelstein Strain Gage Reaction Torque Sensors and Torque
Transfer Standards provide static and dynamic measurement
of driver and load device torque. The Models 2270V and 2280V
are solid flanged devices. The 2270V is the most compact of
the group and occupies considerably less radial space than the
2280V Series. The 2280V Series Torquemeters, have mounting
bolt circles outboard of their body, which simplifies installation.
CF2800V Torquemeters mate directly with NEMA C-Face motors
and generators. Additionally, their large through bore facilitates
many other applications. 2300DV devices have exceptionally
high performance making them ideally suited as Torque Transfer
Standards.
All devices measure torque whether the shaft is rotating or
stationary. They have high safety margins and stiffness, low
deflection and are bidirectional; i.e., their output polarity follows
the torque direction. Reaction torquemeters have no bearing or
speed limitations and don’t require lubrication.
The analog output is factory set to ±10.000V at rated torque;
it may be re-scaled to any value between 1 and 10V. Overrange is
150% or 15V maximum for the analog output. The devices are
linear in Overrange. Engineering Unit digital data is output via an
RS232 port. The same port can be used for re-scaling, invoking
Tare and other control functions. Himmelsteins’ Model 703 in-
strument is compatible and will provide power, engineering unit
torque display, capture max/mins, evaluate limits, provide RS422
and RS485 com ports and much more. When a speed sensor is
available, the Model 723 will also display speed and computed
shaft power.
A. Mechanical Installation
(See Appendix 4 for recommended
attachment bolts and tightening torques)
A.1 Reaction Torque Measurement Explained
Reaction torque measurements are based on Newton’s third law of
angular motion which states, “when a body exerts a torque upon
another body, the second exerts an equal torque upon the first in
the opposite direction and about the same axis of rotation”. To
avoid extraneous load errors (see Sections A3 & D3), the reaction
torque path must be through the torquemeter only. A correctly
installed reaction sensor will accurately measure static and dy-
namic torque whether the test device rotates or is stationary. Under
certain conditions, some dynamic components will not be sensed;
see following discussion.
Referring to
Figure 1
, the test set-up can readily determine
clutch applied torque and, when it slips, clutch peak or slip
torque.
Figure 2
shows a hollow reaction torquemeter measuring
the output torque of an air tool. The torquemeter will accurately
measure the instantaneous tool output torque even though it
rises rapidly (in milliseconds) as the fastener seats. However, all
the reaction torque must pass through the torquemeter - a rotating
union (or equal) must be used at the air supply end to eliminate
shunting part of the reaction torque through the air lines and
thus producing a measurement error. Although it is possible to
satisfy this requirement (no significant unwanted shunt torque
paths) in an air tool application, many other applications can
have significant, unavoidable shunt torque paths which, in
turn, will limit the measurement accuracy. An in-line torque
measurement should be used in such cases.
Figure 3
shows a
measurement similar to
Figure 2
but, with a very important
difference. The torquemeter measures the reaction of the power
absorbing device instead of the power producing device. Assum-
ing no extraneous loads, the torquemeter sees the total reaction
torque of the absorber but, that torque is not necessarily equal to
the motor output torque.
During acceleration (or deceleration), the motor torque equals
the sum of load inertia torques, total load windage torques,
extraneous torques and the pumps’ work load torque. The inertia
torques are the product of angular acceleration and all rotor
inertias except the motors. No reaction measurement can see, or
measure, either the inertia or windage torques. As a result, in a
Reaction
Torquemeter
Coupling
To Amplifier
Torque
Input
Limiting
Clutch
Figure 1. Measuring Clutch Slip Torque
Mounting Plate
Torquemeter
Air Motor
Figure 2. Air Tool torque Measurement