A medical device manufacturer just received an order for a high volume of surgical scissors from a hospital. The manufacturer shares the specifications with its overseas fabricator, which forges, finishes, and sterilizes the scissors. After a final visual inspection, the scissors are sealed into plastic pouches and packed into cardboard boxes. The boxes are loaded […]
Mark-10 defines accuracy as a percentage of full scale of the instrument. To determine the measurement error as an actual load value, multiply the accuracy percentage by the instrument’s capacity.
The accuracy is ±0.1% of full scale (FS). Multiply ±0.1% by 50 lbF, which equals ±0.05 lbF. This means that any displayed reading may be higher or lower by up to 0.05 lbF. For example, if the displayed value is 30.00 lbF, the true reading will be ≥29.95 lbF and ≤30.05 lbF.
The accuracies of the sensor and the indicator must be added together. Models 7i and 5i indicators have accuracy values of ±0.1% FS, while the Model 3i is rated at ±0.2% FS. Using the example of a Series R50 torque sensor with Model 3i indicator, add ±0.35% to ±0.2%, which equals ±0.55%. In a specific example for the Model MR50-12, the accuracy becomes ±0.55% x 135 Ncm = ±0.7425 Ncm.
Because of these fixed errors, lower measured values will be more inaccurate as a percentage of reading.
Further using the example of an M5-50 force gauge, a fixed error of ±0.05 lbF represents a higher error as a percentage of reading for a load of 1.00 lbF than 30.00 lbF.
To calculate the error as a percentage of reading, divide the fixed error by the measured value. For a 1.00 lbF load, the fixed error equals ±0.05 ÷ 1.00 lbF = ±5% of reading. For a 30.00 lbF load, the fixed error equals ±0.05 ÷ 30.00 lbF = ±0.17% of reading.
Because of the relationship between load and accuracy, we recommend selecting an instrument capacity as close as possible to the maximum measured load.
Sampling rate is defined as the rate at which the instrument’s electronics communicate with its load sensor. A faster sampling rate more accurately captures the peak load which occurred during the test. This is especially apparent in applications where the load builds up and falls very quickly – such as the break testing of glass or ceramics. The graphs below illustrate the advantage of a fast sampling rate:
The graph at left shows that an instrument with slower sampling rate may not accurately detect the true peak. In the graph at right, the faster rate accurately captures the true peak.
Sampling Rate vs. Output RateWhile Mark-10 instruments internally sample at up to 14,000 Hz, a typical streaming output rate to MESURgauge software is approximately 25 - 50 Hz. If a faster data collection rate is required, our Series 7 force gauges and indicators can collect data at up to 14,000 Hz, store the data internally, and bulk-download the data to a PC when the test is complete.
This value represents the maximum measurable load. All available capacities are listed for each available unit of measurement. All instruments measure from 0 to the indicated capacity.
Resolution:This value represents the smallest measurable increment. For Plug & Test® sensors, the resolution depends on which indicator is used. Refer to the Capacity x Resolution tables on the particular sensor’s webpage or data sheet.
Example - M5-50 Force Gauge:Pound-force Capacity x Resolution for the M5-50 force gauge is 50 x 0.01 lbF. This means that the gauge measures from 0 to 50 lbF, with increment size of 0.01 lbF, i.e., 0, 0.01, 0.02, 0.03…50.00.
Rundown fixtures contain an internal spring which dampens the rate of increase in torque when a power tool is used, thereby contributing to a more accurate torque measurement. Two fixtures are offered, with different internal spring rates, to address a wide range of applications. Select the AC1066-1 to simulate a soft joint with gradual torque buildup, or AC1066-2 to simulate a hard joint with faster torque buildup. Either fixture is suitable for the full range of torque up to 100 lbFin (11.5 Nm).
Examples of hard and soft joints are provided below:
