DATUM ELECTRONICS
M425 TORQUE TRANSDUCER HANDBOOK
20
Engineering Units
The transducers/sensors are calibrated in engineering units of
either Nm or Lbft.
Full Scale Output
The mV/V is the output from the transducer when the rated
load in applied.
mV/V
To measure torque we use a bridge network of resistive strain
gauges. These change resistance with the applied strain. The
output they give is a ratio of the voltage applied and the mV
change in signal from the bridge.
This mV/V ratio is normally quoted in the form
1.55mV/V = 1000Nm. The mV/V value is established at
calibration by applying a known torque to the shaft. This
ratio will remain constant for the life of the transducer/sensor
unless damaged.
Noise
Irregular fluctuations that accompany a transmitted electrical
signal but are not part of the data generated from the sensor.
Proof Load
The proof load is the load to which the transducer/sensor
has been tested - occasional loading to this level should not
damage the transducer. Repeated loading to this level will
reduce the fatigue life of the transducer and may cause small
zero offset over time (usually measured in either Nm or lbft).
Rated Load
The Rated Load is the design full load of the transducer/
sensor (measured in either Nm or lbft).
GLOSSARY OF TERMS
Raw Data
Raw data is the raw strain level from the torque shaft.
It will include any zero offset.
The scaling of the raw data will require:
Torque [Nm] = (raw data [mV/V] - zero offset [mV/V]) x (rated
torque [Nm]) ÷ (full scale output [mV/V]).
Sensor
A sensor measures a physical quantity and converts this into
a signal. The physical quantity is torque or torsional strain,
this is converted into serial data.
NOTE:
The words transducer and sensor are often used in
this context to mean the same thing.
Span
This is the value of output at the rated load. Either given in
terms of mV/V signal or Nm or lbft when in engineering units.
STEP files
A STEP file is a widely adopted CAD file format used to share
3D models between users with different CAD systems.
Torque
The twisting force on the shaft created by the driving force
(motor) and the resisting force (brake or gear).
Transducer
A transducer is defined as a device that converts one form of
energy to another. In terms of the M425 Torque Transducer
the transducer converts torque into serial data.
NOTE:
The words transducer and sensor are often used in
this context to mean the same thing.
Zero
This is the value of the signal when the shaft is completely
unloaded. Normally quoted in mV/V.
MAINTENANCE
SERVICEABLE ITEMS: BEARINGS
If you have requirements for high duty sensors where bearing
life may be a concern due to other external loads, ask our
support team for additional information on our bearing less
RS425 and FF425 ranges. These RS/FF designs provide a high
degree of flexibility with regard to mounting tolerances and
maintenance free operation.
If the shaft of the Transducer is bent the balance of the
Transducer will be disturbed and the bearing life will be greatly
reduced. Excessive load or mounting misalignment will also
effect the life of the bearings. Bearings can be service by return
to Datum Electronics.
The bearings are the only component on the M425
that may require servicing depending on operating
conditions. The following provides information on
the bearing life under load conditions.
The M425 Transducer has a balanced rotor running between
your couplings. The body of the Transducer is supported by
two bearings. The life of the bearings at normal running
RPM of half the rated RPM is 10 years continuous use.
