Service

Frequently Asked Questions

Load

Can you get an amplified signal from a load cell?

What are the different performance specifications and what do they mean?

What are the different units of force and what do they mean?

What can affect a load cell’s measurements?

Why are there so many different types of load cells?

Pressure

What are the different performance specifications and what do they mean?

What are the different units of pressure and what do they represent?

What can affect a pressure transducer’s measurements?

What do extended abbreviations, such as psia or psid, mean?

Torque

What are the different performance specifications and what do they mean?

What are the different units of torque and what do they mean?

What can affect a torque transducer’s measurements?

What is the difference between reaction and rotary torque transducers?

General

What is shunt calibration?

What is TEDS?

Load

What are the different performance specifications and what do they mean?

Each specification gives the maximum error range for a given load cell’s output (usually as a percentage of full scale output) in regard to a specific characteristic. There are four main specifications which are critical to understanding load cell performance.

First, non-linearity determines how much the output deviates from a perfectly straight line.

Second, hysteresis gives the difference between the descending and ascending outputs.

Third, repeatability is the measure of how consistently the output repeats from run to run.

And fourth, thermal effects show the error in output that occurs as the result of a temperature change. The combined error of all these specifications does not exceed one percent for almost all load cells, and it may be as low as a few hundredths of a percent for the most precise.

What are the different units of force and what do they mean?

In the US, the most widely used unit for force is the pound. It was historically defined in relation to avoirdupois units, but currently this definition has been replaced by one which is expressed in metric units.

The SI unit for force is the Newton (N), which is defined as the force required to accelerate one kilogram of mass at a rate of one meter per second squared.

Other units of force include the dyne, the kilopond, the poundal, and the grain, but these are not nearly as common and utilized mostly in specialized cases.

What can affect a load cell’s measurements?

Many variables can influence a load cell’s performance characteristics.

Testing errors can arise from improper loading conditions like off-center loading, side loading, and torque loading.

Set-up conditions related to the cleanliness, hardness, and flatness of the upper and lower loading surfaces may also introduce inaccuracies.

Additionally, environmental conditions such as temperature, humidity, and electrical noise, as well as high vibrations, extended cycling, and others are able to impact the output signal.

For these reasons, it is important to consider all such factors before choosing a load cell, and to contact the manufacturer to ensure that the load cell matches the application.

Why are there so many different types of load cells?

The abundance of load cell designs stems from the even greater variety of load cell applications. For instance, donut load cells are commonly used to monitor bolt tightening, which requires that they have an unthreaded through-hole and a low profile.

Another example is the cantilever beam, typically employed in weighing applications which require it to be anchored at one end and hold weight at the other, hence the elongated body.

In truth, the many different types of strain gauge load cells all operate on the same basic principles—the piezoresistive effect and the Wheatstone bridge configuration—so in this sense, they are really not very different at all.

Pressure

What are the different performance specifications and what do they mean?

Each specification gives the maximum error range for a given pressure transducer’s output (usually as a percentage of full scale output) in regard to a specific characteristic.

There are four main specifications which are critical to understanding pressure transducer performance.

First, non-linearity determines how much the output deviates from a perfectly straight line.

Second, hysteresis gives the difference between the descending and ascending outputs.

Third, repeatability is the measure of how consistently the output repeats from run to run.

And fourth, thermal effects show the error in output that occurs as the result of a temperature change.

The combined error of all these specifications does not exceed one percent for almost all pressure transducers, and it may be as low as a few hundredths of a percent for the most precise.

What are the different units of pressure and what do they represent?

In the US, the most widely used unit for pressure is the pound per square inch or psi. As its name implies, one psi is equivalent to a force of one pound over an area of one square inch.

The SI unit for pressure is the pascal, which is defined as a force of one newton over an area of one square meter

Other units derived from the pascal include the bar, equal to 10,000 pascal, and the standard atmosphere (atm), equal to 101,325 pascal. Another common pressure unit is the torr (closely related to mmHg), which is defined as 1/760 of an atmosphere, and thereby is also indirectly derived from the pascal.

What can affect a pressure transducer’s measurements?

Many variables can influence a pressure transducer’s performance characteristics.

Set-up conditions related to the pressure medium, fixture tightening, and mating port may also introduce inaccuracies.

Additionally, environmental conditions such as temperature, humidity, and electrical noise, as well as high vibrations, extended cycling, and others are able to impact the output signal.

For these reasons, it is important to consider all such factors before choosing a pressure transducer, and to contact the manufacturer to ensure that the pressure transducer matches the application.

What do extended abbreviations, such as psia or psid, mean?

In each case, the extra letter indicates the reference point for the pressure measurement.

Absolute pressure (psia) indicates that the measurement is given relative to a total vacuum.

Differential pressure (psid) indicates that the measurement is given relative to some other pressure source.

Gauge pressure (psig), or more exactly vented gauge pressure (psivg), means that the measurement is given relative to local pressure.

Sealed pressure (psis), or more exactly sealed gauge pressure (psisg), means that the measurement is given relative to some sealed chamber which usually holds standard atmospheric pressure.

All these different measurements of pressure are usually a positive number, which indicates that the measured pressure is greater than the reference pressure, and this is always the case for absolute pressure.

Torque

What are the different performance specifications and what do they mean?

Each specification gives the maximum error range for a given torque transducer’s output (usually as a percentage of full scale output) in regard to a specific characteristic.

There are four main specifications which are critical to understanding torque transducer performance.

First, non-linearity determines how much the output deviates from a perfectly straight line.

Second, hysteresis gives the difference between the descending and ascending outputs.

Third, repeatability is the measure of how consistently the output repeats from run to run.

And fourth, thermal effects show the error in output that occurs as the result of a temperature change.

The combined error of all these specifications does not exceed one percent for almost all torque transducers, and it may be as low as a few hundredths of a percent for the most precise.

What are the different units of torque and what do they mean?

In the US, the most widely used unit for torque is the foot-pound (ft-lb). As its name implies, one foot-pound is equivalent to the torque of one pound of force applied at a distance of one foot from a pivot.

The SI unit for torque is the newton-meter (N·m), which is similarly defined as the force of one Newton applied at a distance of one meter from a pivot.

Other units of torque include the inch-pound, inch-ounce, and the kilogrammeter.

What can affect a torque transducer’s measurements?

Many variables can influence a torque transducer’s performance characteristics.

Testing errors can arise from improper loading conditions like off-center loading and side loading.

Set-up conditions related to the cleanliness, hardness, and flatness of the loading surfaces and tightening requirements may also introduce inaccuracies.

Additionally, environmental conditions such as temperature, humidity, and electrical noise, as well as high vibrations, extended cycling, and others are able to impact the output signal.

For these reasons, it is important to consider all such factors before choosing a torque transducer, and to contact the manufacturer to ensure that the torque transducer matches the application.

What is the difference between reaction and rotary torque transducers?

Reaction torque transducers measure non-rotating torques, and therefore must be affixed to stationary surfaces. They employ many of the same concepts and technologies that apply to load cells.

Reaction torque transducers are often used to measure torques involved in bolt tightening, container sealing, and engine start-ups.

Rotary torque transducers measure rotating torques, and therefore must be able to rotate freely and continuously. They may utilize strain gages, but frequently rely on other technologies.

Rotary torque transducers are most often used to measure torques involving crankshafts and engine outputs.

General

What is shunt calibration?

Shunt calibration is a technique for simulating a load in a strain gage sensor in order to determine if a sensor is in calibration without applying an actual load. In this method, one leg of the Wheatstone bridge circuit is shunted using a resistor of a known value. If the circuit is working properly the resulting output is predictable and useful for calibrating or scaling the sensor.

What is TEDS?

T.E.D.S stands for Transducer Electronic Data Sheet. This option makes a sensor ‘plug-and-play’ by digitally storing setup and calibration data in the sensor itself. Upon connection to a compatible data acquisition system, setup information is automatically downloaded and the sensor is ready to use. The IEEE 1451.4 standard has been adopted and is available on the most widely used data acquisition systems.

Can you get an amplified signal from a load cell?

Yes, load cell signals can be amplified. We offer internal amplification if the load cell is large enough, and in-line or in-cable amplifiers for the small and miniature units. All outputs are available including 4-20mA (2- or 3-wire), 0-5Vdc, or 0-10Vdc.