How to choose a load cell
Step 1---Define your requirements
Measuring range: This will decide the load cell capacity,capacity to choose.
Output signal: Typical output of a load sensor is 2.0mV/V,0-5V or 4-20mA is also achievable through internal or external amplifier.
Load direction: Tension?Compression?Tension and compression?
Working temperature: Different strain gauges and accessaries will be used for different temp. range.
Material: Aluminum,alloy steel or stainless steel?
Mounting: Female/Male thread,In-line,Side Mount,Flange Mount,Thru-hole,or other structure?
Accuracy: Different application has different error tolerance and some load cells have relative low accuracy.
Environmental protection: Anti-electromagnetic interference,anti-explosion,dustproof,waterproof ?
Sampling frequency: Different force sensor has different natural frequency.
Other requirements like electrical connection,cable length,installation space,etc.
Step 2---Get to know about load cell
Load cell(Force sensor,force transducer): A measuring device which converts mechanical force into electrical signal which is proportional to the applied force.
Rated capacity: The maximum axial load that the transducer is designed to measure within its specifications.Active redundancy should be considered when choosing the capacity.
Rated output(Sensitivity): The signal produced by force transducer when rated capacity is applied, expressed in terms of mV/V.
Resolution: The smallest change in mechanical input which produces a detectable change in the output signal.
Zero balance: The output signal of the force sensor with no-load applied.
Non-repeatability: The maximum difference between force sensor output readings for repeated loadings under identical loading and environment conditions.
Non-linearity: The maximum deviation of the calibration curve from a straight line drawn between the no-load and rated capacity outputs,measured on increasing load only.
Hysteresis: The maximum difference between the load cell output readings for the same applied load;one reading obtained by increasing the load from zero and the other by decreasing the load from rated output.
Creep: The change in load sensor output occurring with time,while under load,and with all environmental conditions and other variables remaining constant,defined by a certain time like 30min.
Safe overload: The maximum load that can be applied without producing a permanent shift in load cell performance.Specified as a percentage of the capacity (i.e.150% of F.S.).
Ultimate overload: The maximum load that can be applied without physical destruction to force sensor. Specified as a percentage of the capacity(i.e.200% of F.S.)
Compensated temperature: The range of temperature over which the load cell is compensated to maintain rated output and zero balance within specified limits.
Operating temperature: The limits of temperature within which the force transducer will operate without permanent adverse change to any of its performance characteristics.
Temperature shift on zero: The change in zero balance due to a change in force sensor working temperature.
Temperature effect on output: The change in output due to a change in load cell working temperature.
Natural frequency: The frequency of free oscillation under no-load conditions.
Step 3---Choose suitable load cell according to your application.
With the development of sensor technology, custom design is getting increasingly common. Customizable variables include:
Capacity
Rated output(mV,0-5V,0-10V,0-20mA,4-20mA)
Material(Al,alloy steel and stainless steel)
Dimensions
Electrical connection
Ingress protection class
Working temp.
Other parameters are crucial to your application.
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