This in-depth presentation is a detailed crash course on load cells and force measurement for a wide variety of applications. Learn more about our history, unparalleled track record and our products.

1. Lunch & Learn
Interface: Brian Peters, Ken Vining
T&M Instruments: Jace Curtis

2. Lunch & Learn Topics
• Interface History
• Load Cell Design & Theory
• Application Considerations
• Factors of Performance
• What Makes Interface Better
• Questions?

3. Our Heritage
• Family owned in Scottsdale, AZ since 1968
• World’s largest manufacturer of low profile load
cells
• Guarantee: Our load cells will outperform our
competitor’s – PERIOD
• Made in the USA

4. Trust our Experience
• We’ve been in the business of manufacturing
load cells for 45 years
• Building our 1 millionth load cell in 2013!
• Both PTB & NIST are Government standards for
measurement traceabilty: They use INTERFACE

5. Performance Second to None
• Metrology grade load cells with performance as
high as 0.02% F.S.
• Lower load limit of 4% on Gold Standard series
cells and 2% on Platinum Series
• Provide additional specifications not standard in
the industry
• A2LA Accredited calibration

6. Vast Capabilities
• Performance: as high as 0.02% F.S.
• Capacity: 50 grams to 2.25 Million lbf
• Millivolt, Voltage or Current output available
• Hermetically sealed, submersible, vibration rated,
dual bridge, overload protected
• ATEX approved for hazardous environments
• 200 page catalog represents 60 – 70% of our
business. The rest is modified standard or custom

7. We Sell Solutions
• Application engineers will discuss your
application to understand your priorities in your
force or torque measurement
• We will propose a solution specific to your
application be it a standard, modified or custom
design
• This has been our approach for 45
years…there’s a good chance we already have a
solution to meet your needs

8. Over 100,000 configurations of
load & torque cells

9. Over 10,000 instruments and
signal conditioners sold in last
10 years alone

10. What is a Load Cell?

11. How a load cell works
• Wheatstone bridge
• 2 voltage dividers fed
by the same input
creating a balanced
bridge.

12. How a load cell works
• Deflection causes an
offset or unbalanced state
which creates a change
in resistance.
• The result is a ratiometric
output directly
proportional to the force
applied.
• Specified as mV/V output

13. Choosing the Right Load Cell
• Application considerations – what is
important?
• Mechanical (dimensions & mounting)
• Electrical (output & excitation)
• Environmental (temperature, moisture, etc)
• Performance (accuracy, thermals)

14. Choosing the Right Load Cell
• Mechanical - Mounting
• One of the most critical aspects
that can determine the success
of your application
• Various possibilities: Threaded
connections, adhesive, inline,
through hole,
• Direction of load will impact
your decision of the best
approach

15. Low Profile mating surface
• Surface must be clean and flat
• Mounting surface must be flat to 0.0002 Total Indicator
Reading
• Suitable thickness and material
• Recommended hardness of Rc 30 or higher
• Mounting bolt torque according to specifications

16. Design Alternatives
• Many choices to choose from

17. Choosing the Right Load Cell
• Electrical
• Excitation voltage available
• Millivolt, voltage or current output
• Acceptable input to data acquisition
• Noise immunity
• Cable length
• Proper grounding

18. Choosing the Right Load Cell
• Environmental – Thermals

19. Choosing the Right Load Cell
• Environmental – moisture or humidity?
• Dual diaphragm, or welded, sealed units available
• High humidity, splash down or oil bath applications
can be addressed
• Nema or IP ratings as industry standards
• Some designs cannot be sealed at all
• Take caution selecting cable
• Environmental connectors available

20. Choosing the Right Load Cell
• Environmental - submersible
• Underwater applications are a possibility
• Media density and depth need to be understood
• Barometric pressure compensation
• Susceptibility to media/corrosion
• Vented cable?

21. What Major Factors
Impact Sensor
Accuracy in Testing
Applications?

22. Factors
• Specifications
• Mounting
• Calibration
• Instrumentation
• Cables
• Uncertainty of calibration

23. Specifications
• No “Accuracy” term on
data sheets
• Apply specifications
according to application
• %FS, %RO, %, %/°F,
time related

24. Nonlinearity
The algebraic difference
between OUTPUT at a
specific load and the
corresponding point on the
straight line drawn between
minimum load and
maximum load. Normally
expressed in units of %FS.

25. Hysteresis
The algebraic difference
between output at a given
load descending from
maximum load and output
at the same load ascending
from minimum load.
Normally expressed in units
of %FS.

26. Static Error Band
The band of maximum
deviations of the ascending
and descending calibration
points from a best fit line
through zero output. It
includes the effects of
nonlinearity, hysteresis, and
non-return to minimum load.
Expressed in units of %FS

27. SEB Output
A computed value for Output at capacity
derived from a line best fit to the actual
ascending and descending calibration
points and through zero Output.

28. Interface compensates every low profile load cell
Each load cell is tested, adjusted, and retested until it is within
required performance tolerance
A history of every load cells moment compensation data is retained
Graphs of moment load test results can be provided
Eccentric Load Sensitivity
• ECCENTRIC LOAD - Any load applied
parallel to but not concentric with the
Primary Axis. Results in Moment load.
• SIDE LOAD – Any load at the point of Axial
Load application at 90° to the primary axis.

29. Maximum allowable off-axis loads
vary by model as shown

30. Moment and Side Load Error Limit
Example
Assume Model 1220ACK-
50K-B Spec
Limit
Load
Cell
Capacity
Allowable
Extraneous
Load
Maximum Error Due to
Allowable Extraneous
Loads
Eccentric Load Sensitivity
(% per inch) ±0.25 50K lbf
(40% capacity) x
(1 inch) 20K in-lb
(20K in-lb) x (0.25%/in) /
50K lbf 0.10%
Side Load Sensitivity (%) ±0.25 50K lbf 40% capacity 20K lbf
(20K lbf) x (0.25%) / 50K
lbf 0.10%
Assume Model 1110ACK-
10K-B Spec
Limit
Load
Cell
Capacity
Allowable
Extraneous
Load
Maximum Error Due to
Allowable Extraneous
Loads
Eccentric Load Sensitivity
(% per inch) ±0.10 10K lbf
(40% capacity) x
(1 inch) 4K in-lb
(4K in-lb) x (0.10%/in) /
10K lbf 0.04%
Side Load Sensitivity (%) ±0.10 10K lbf 40% capacity 4K lbf
(4K lbf) x (0.10%) / 10K
lbf 0.04%

31. Creep
• The change in load cell signal occurring with
time while under load and with all
environmental conditions and other variables
remaining constant. Expressed as % applied
load over specific time interval.

32. Temperature Compensation
Temperature effects both zero balance
and output signal
Errors can either be positive or negative
Effects are repeatable from test to test

33. Temperature effect on output
Expressed as a
% of Reading / °F
Effects the slope of the
output curve

34. Temperature effect on zero
Expressed as
%Rated Output / °F
Shifts entire curve
parallel to itself
Relatively larger effect
at lower signals

35. Typical Interface Specs for
Temp Effect on Zero Balance
1100 Spec
– High Accuracy
– ± .0004%RO / °F
1200 Spec
– Medium Accuracy
– ± .0008%RO / °F
As specified by
customer

36. Temperature Compensation of ZB
Every load cell is temperature
compensated for zero balance
Compensation flattens the curve
about room temperature
A history of temp comp data for
every load cell is retained
Shape of curve isn’t changed by
compensation
Standard compensated
temperature range is 15ºF to
115ºF
Interface will perform temp
compensation at your requested
temperatures

37. Symmetry Error
The algebraic difference between the
Rated Output in tension and the average
of the absolute values of Rated Output in
tension and compression. %RO

38. Mounting Considerations
Extraneous loads
Parasitic load paths
Mating surface and adapters
Live end vs. Dead end

39. Live End vs. Dead End

40. Calibration
Characterization
Calibrate as used in application
Additional points
Ascending and descending points
Multiple runs
ASTM E74

41. 3-Run calibration

42. Nonrepeatability
The maximum difference between output
readings for repeated loadings under
identical loading and environmental
conditions. Expressed in units of %RO

43. Cable Length
Lowered sensitivity
Increased temperature
error
6-wire vs. 4-wire

44. Instrumentation
Zero adjustment
Span adjustment
– Applied load
– mV/V input
– Simulator
– Shunt calibration

45. Simulator
Connects in place of load
cell
Ratiometric mV/V output
Can be used to calibrate
instrument in mV/V

46. Shunt Calibration
Shunt calibration uses a resistor to
stimulate one leg of the wheatstone bridge
The resulting output signal can be useful
for calibrating or scaling instrumentation
Resistor tolerance is generally unimportant
but TCR should be carefully considered
Resistors may be internal or external to
the load cell
Internal resistors don’t get lost

47. Shunt Calibration
Internal shunt cal can also be used to
determine to which bridge a remote
connection has been made, assuming
each bridge has a different resistor value
When using external shunt cal, remember
long cable lengths affect shunt cal values

48. We provide solutions

49. Vast Range of Load and Torque
Sensing Solutions
• Clevis pin
• Miniature
• Sub-miniature
• Load buttons
• Load washers
• Axial torsion
• Multi-axis
• Low Profile (pancake)
• Column design
• S Beam
• Single point
• Diaphragm design
• Through Hole
• Rotating torque
• Reaction torque

50. Why Should you Choose Interface?
Capabilities
• Capacities from 10 grams to 2,250,000 lbf
• Accuracy as high as 0.02% FS
• Internally amplified (4-20mA, 0-5V, 0-10V)
• Hermetically Sealed
• -65˚ - 400˚F thermal compensation
• Multiple bridge configuration

51. Why Should you Choose Interface?
Capabilities
• Fatigue rated
• ATEX, FM, CE, RoHs ratings available
• Submersible – IP68
• Dual diaphragm
• Overload protection
• TEDS IEEE 1451.4
• Customer specified electrical & mechanical
connection

52. 40% of our business
is custom or special

53. Why Should you Choose Interface?
Performance second to NONE
• Guarantee: Our load cells will outperform our
competitor’s – PERIOD
• There are fundamental reasons why we can
make that claim

54. Vertically Integrated Manufacturing
• All machining, gaging and fabrication controlled in house
Why Should you Choose Interface?

55. Stocking program
• Interface will maintain stock of the finished goods for same day
shipment if orders are received by noon MST.
• Interface maintains a perpetual inventory subassemblies of
standard products. This practice minimizes availability to 10
days or less. No other competitor can match this capability.
• When availability is a concern, please contact the factory to
discuss your needs
Why Should you Choose Interface?

56. What’s behind our performance
guarantee?

57. What makes Interface Better?
Proprietary Interface Strain Gages
• Made in house at our facility in Scottsdale, AZ
• Feature: Interface strain gages precision matched to
counteract the temperature characteristics of the
modulus of the load cell structural material
• Benefit: The output is temperature insensitive and
does not require compensation resistors which
produces simpler and more reliable circuit.

58. What makes Interface Better?
Feature: Proprietary Interface Strain Gages
• Benefit: Compensation resistors cannot be thermally connected with the
cell’s flexure which results in dynamic thermal performance, resistance
to thermal gradients, and delayed thermal response
• Benefit: Elimination of modulus comp resistors allow for higher output

59. What makes Interface Better?
Feature: Proprietary Interface Strain Gages
• Benefit: Our strain gages allow us to provide a higher
output - 4mV/V
• Competitors provide 3mV/V or less
• Benefit: Higher signal-to-noise ratio
• Benefit: Higher resolution in precision measurement
applications
• Benefit: Superior fatigue life compared to Constantan

60. What makes Interface Better?
Feature: Rigorous Temperature Testing
• Interface performs both hot and cold thermal compensation from
15˚ - 115˚F
• Most competitors provide only the hot side (60˚ - 160˚F)
• Benefit: The slope of the curve is much flatter near room
temperature and identical at both ends of the slope. The result
is minimal variation across the entire thermal range.
• Custom calibrated ranges available

61. Feature: Moment compensation
• Interface compensates every low profile load cell
• Competitors do not know their performance in
this regard
What makes Interface Better?

62. Eccentric & Side Load Specifications
What makes Interface Better?

63. What makes Interface Better?
Feature: Moment Compensation
Benefit: Known maximum error

64. New Product Releases

65. New Product Releases
 New and Improved Low Profile
 Better overall static error specifications
 Enhanced off axis performance
 Improvements will be implemented at no additional cost to
customer
 STEP files are available for download via website

66. New Product Releases
 Flange load cell
 Extremely popular in Europe
 Ease of installation due to elimination of thread alignment issues
 Good alternative especially with large thread diameter

67. New Product Releases
Model 2300 flange load cell
 0.05% F.S. static error band
 High capacity: 1M lbf
 Eccentric load compensation
 Ease of installation
 Gaining popularity in Europe

68. New Product Releases
 Load Pins
• Capacities from 100 lbs to 300,000 lbs
• Various sizes and shapes, lengths and diameters
• Small quantity orders are acceptable
• ATEX rating for hazardous environment

69. Load Pin Configurator
 Lots of choices
Diameter
Sensing section length
Anti-rotation techniques
Cable exit
Amplified output?