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"Quality 101: An Introduction to Gage R&R"
04 May 2012
- Identifies sources of variation in measurement
- Defines part-to-part variation, repeatability and reproducibility
- Shows how Gage R&R helps determine if a measurement system meets your requirements and helps identify the sources of variation within a system
Click here to view the article.
As always, if you have any questions related to this material, our support staff at Cooper Instruments is available to help. Contact them by calling (800) 344-3921 or emailing This e-mail address is being protected from spambots. You need JavaScript enabled to view it .
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Conversely, a data set where all points fell between 499.8 and 500.0 would meet the qualifications for accuracy and repeatability.
How to Select the Right Torque Load Cell
29 March 2012Understand your Application
First, you must determine that you want to measure torque. Applications for torque sensors include determining the amount of power an engine, motor, turbine, or other rotating device generates or consumes. In the industrial world, you may encounter quality control specifications that require companies to measure torque during manufacturing, especially when fasteners are applied.
Next, you’ll need to determine if you are going to measure reaction or rotary torque. A rotary torque sensor is used when you need the transducer itself to rotate, whereas reaction torque transducers are used to measure torque loads where the sensor doesn't have to rotate, as they will only rotate as much as the shaft will deflect (if you turn them too much, they will overload or break). Another component in understanding your application will be your testing environment. Will the sensor be exposed to extreme temperature, corrosive liquids, intense vibration, etc.? Other considerations that may influence your final decision are size, cost, availability and special requirements.
Define your Capacity Requirements
As with load cells, you’ll want to choose a capacity over the expected maximum operating torque, so as not to accidentally overload the sensor. Don’t forget to factor in all extraneous torque and over hung loads before deciding on the capacity you’ll need. While a torque transducer is capable of measuring torque accurately with some radial load, as the radial load increases to the point where an appreciable moment load is applied to the shaft, the resulting deflection will cause output error. You also need to determine if you’ll be using the sensor for testing clockwise, counterclockwise or both.
Define your Needs
Consider how you’ll be mounting your sensor (for example: flange to flange, square drive, shaft to shaft, etc). If your application requires a rotary sensor, you need to define the RPM requirement for your sensor also. You want to make sure that you mount the sensor in such a way that it "sees" only rotational loading, if possible and not radial loading from whatever is attached. However, one must be cognizant of how support bearings, if employed, can cause errors through drag force caused by bearings and seals. This is also the point at which you’ll want to consider size, connectors, accuracy and cost. What kind of output will you need – mV/V, VDC, mA? Finally, determine if you need a built-in encoder to measure speed and angular deflection
or position.
Select Instrumentation (if necessary)
If you need an instrument for your application, select it at the same time you select the pressure sensor. This will help ensure the compatibility of the entire system. Don’t forget to purchase system calibration with your order. This integrates your sensor and instrument as one system.
These are suggestions to help point you in the right direction when selecting your torque sensor. Of course, our knowledgeable sales staff is also available to help you select the best equipment for your application.
Whitepaper: Does New "Stuff" Need to Be Calibrated?
22 March 2012In this white paper found on Quality Magazine’s website, Hill Cox, discusses:
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The importance calibrating “new stuff” (his technical term for new, unused gages)
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Why you shouldn’t assume that your new gage meets the specifications that it should
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What he feels is the only way to ensure that your items are good on the way in – calibration
Click here to view the white paper.
Of course at Cooper Instruments, we understand these problems and work hard to ensure that every product we sell is delivered in working order and within stated specification. We are also capable of providing calibration checks on any manufacturer’s load cell system.
As always, if you have any questions related to this material, our support staff at Cooper Instruments is available to help. Contact them by calling (800) 344-3921 or emailing This e-mail address is being protected from spambots. You need JavaScript enabled to view it .
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Types of Load Cells
16 February 2012
To wrap up the discussion we’ve been having over the past several weeks, we’d like to discuss the different types of strain gauge load cells available and how to know which style is right for your application.
S-Beam Load Cells: These are used for tension applications, often when hanging or suspending a weighing system. They are so named because of their shape and are also sometimes called Z-Beam load cells. With high precision, low cost and easy installation, s-beam load cells are among the most popular, but they are designed solely for in-line applications and are very sensitive to off-center and extraneous loads. The LFS 210 is Cooper Instruments’ best-selling s-beam load cell.
Beam Load Cells: These load cells get their name from their shape, which is rectangular. Some typical applications include tank, hopper or silo weighing. Cooper Instruments’ most popular beam load cell offering is the shear beam LQB 610. Beam load cells are divided into several sub-categories.
Shear Beam: Shear beam load cells have an actual “shear” machined inside to protect the cell from side loading forces. ‘Single-ended’ shear beams are used for medium capacity weighing while ‘double-ended’ shear beams are used for higher capacities.
Bending Beam: Often used in bench scales, bending beams must be installed with care to avoid side-loading.
Canister Load Cells: These (shockingly) canister-shaped units were the first strain gauge load cells designed. Today they are typically used for high (100,000 lb+) capacity compression applications. See our LRCN 710 for an example of a canister load cell.
Pancake Load Cells: Also called Low Profile load cells, pancake load cells (like the LGP 310) offer high precision with less sensitivity to load condition. Sometimes they are designed with multiple shear struts and sometimes with bending beams. They typically have a female thread through the center and a ring of outer holes for mounting, so they can be used in either compression or tension (by using the outside mounting holes).
(Load) Button Load Cells: These are round load cells with a small, raised ‘button’ in the center, like our LKCP 410. They are comparatively small in size making them ideal for use in limited space and are used for compression applications. Common uses are in the medical and automation fields where space is often an issue and the load cell must be small in size.
Thru-Hole (Donut) Load Cells: Shaped like donuts, thru-hole load cells are used for bolt force measurement, clamping force, post or leg mount and many more applications. They offer high accuracy and high stiffness for applications requiring compression, off-center or press loading. Cooper Instruments’ LKCP 48X series are donut load cells.
As always, if you have any questions related to this material, our support staff at Cooper Instruments is available to help. Contact them by calling (800) 344-3921 or emailing This e-mail address is being protected from spambots. You need JavaScript enabled to view it .
We’d love to hear your feedback regarding this or any other article we’ve posted. To leave feedback, ‘Like’ us on Facebook and then post your feedback on our wall.
How a Strain Gauge Fits into a Load Cell
09 February 2012In the last two weeks, we explored strain and then strain gauges . Next in the series, we’ll discover how that strain gauge fits into a load cell.
We have this strain gauge and we know that subjecting it to force causes it to deform and its electrical resistance to change. Last week, we briefly mentioned that a Wheatstone bridge is used to help us read this change. According to Wikipedia, a Wheatstone bridge is “an electrical circuit used to measure an unknown electrical resistance by balancing two legs of a bridge circuit, on leg of which includes the unknown component.” A basic Wheatstone bridge circuit contains four resistances (four strain gauges), a voltage input*, and a voltmeter. This Wheatstone bridge configuration is used because the use of four strain gauges amplifies the amount of change in the resistance, making it easier to read and more accurate, as well as less sensitive to thermal changes.
*The voltage input into the Wheatstone bridge could be constant or not. If the amplifier is ratiometric (able to measure the input voltage relative to the output voltage) then constant input voltage is not necessary.
The four strain gauges are configured in such a way that the current from the power source splits, flows through the sequence of resistors, then recombines into a single conductor (image). Three of these resistors have known values. The value of the fourth resistor is not known. As the strain gauge is loaded, the bridge becomes unbalanced producing an indication at the voltmeter. So a known voltage is input into the circuit and then the output voltage should be slightly different due to the change in electrical resistance of the strain gauge when loaded.
(Click here for cool pictures of Wheatstone bridges.)
So when these elements, the strain gauges configured as a Wheatstone bridge, are bonded to an engineered physical structure, the overall package is called a load cell. Wikipedia defines a load cell as “a transducer that is used to convert a force into electrical signal.” Although other types of load cells exist, strain gauge load cells are the most popular and surpassing all other types because manufacturers continue to increase their accuracy and lower their costs.
As always, if you have any questions related to this material, our support staff at Cooper Instruments is available to help. Contact them by calling (800) 344-3921 or emailing This e-mail address is being protected from spambots. You need JavaScript enabled to view it .
We’d love to hear your feedback regarding this or any other article we’ve posted. To leave feedback, ‘Like’ us on Facebook and then post your feedback on our wall.
