8.6 Load Cell Corrections Setting WARNING
8.6.4 Enable Deflection Compensation Deflection compensation is a feature within your L3 system that corrects and compensates for the total deflection effects due to frame deflection, load cell sensor deflection and test fixture deflection. Deflection compensation may be used in either tensile or compressive testing. Spring compression testing can benefit from deflection compensation since even very minor deflection effects can result in erroneous readings and calculations of spring rate. Compensating for deflection can be done by allowing the entire “grip string”, comprised of the load cell sensors attached to the frame and platens affixed to the load cell to be compressed against a hard stop. For example, allowing the top compression platen to compress against the lower compression platen at a very low speed and to a specified load capacity that is well within the load cell capacity. WARNING Deflection compensation, performed incorrectly, can result in permanent damage to the load cell sensor. Deflection compensation should be performed by your Starrett representative or personnel who have been trained, or who are experienced in performing deflection compensation on Starrett systems. If you expect your load measurement during your test to be 10lbf, you will want to compensate for deflection up to 10lbf. To determine your deflection compensation values, you would bring your compression platens together so they are barely touching one another, or just touching one another without a significant load (below 1% of the target load of 10lbf. Zero the Distance. With the jog speed set at Slow Speed, press the jog key downward causing the crosshead to move downward until you reach the target load value of 10lbf. Record the Distance value that the crosshead traveled to get to the target load of 10lbf. This Distance value is the Deflection Distance. The Deflection Force is the target load value, e.g. load at the Deflection Distance value. 8.6.4.1 Deflection Distance The Deflection Distance is the distance the crosshead traveled from a zero position to the target load value. 8.6.4.2 Deflection Force The Deflection Force is the target load value, e.g. load at the Deflection Distance value.
The Load Cell Correction functions should be restricted to personnel who are authorized to calibrate a Starrett load cell sensor. Use by inexperienced and untrained personnel can result in permanent damage to the load cell sensor and your testing system. The Load Cell Corrections setting is used for calibrating a load cell that is connected to your testing frame. This section will describe some of the functions available. The procedures for calibrating a Starrett load cell sensor may be obtained through your Starrett representative.
L3 LOAD CELL CORRECTIONS Setting Used for calibrating load cell sensors and test frame 8.6.1 Enable LEC (Linear Error Correction) Linear Error Correction (LEC) is normally set to Yes. This algorithm continuously evaluates test frame displacement and applies correction to ensure that displacement measurements are maintained to within published specifications. 8.6.2 Distance Nominal When a full system calibration is performed and displacement is calibrated per ASTM E2309/2309M (or equivalent), the nominal value used during calibration is entered into this field. This value is taken from the artifact used to calibrate or verify displacement. 8.6.3 Distance Observed When a full system calibration is performed and displacement is calibrated per ASTM E2309/2309M (or equivalent), the observed value used during calibration is entered into this field. The Observed value is the value displayed by the L3 Workstation connected to the test frame.
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