The Technology of Flexibility: Detection Techniques in Stiffness Testers

The Technology of Flexibility: Detection Techniques in Microcomputer Bending Stiffness Testers

The ZY-TDY300 microcomputer bending stiffness tester employs a combination of precise mechanical control and sensitive electronic detection to accurately determine the bending stiffness of flexible materials. This article explores the key detection techniques utilized by this instrument.
 

1. Displacement Measurement for Angle Determination:

To accurately measure the bending angle, the instrument utilizes displacement sensors, such as rotary encoders or potentiometers, integrated with the bending arm or probe. As the arm moves to bend the sample, these sensors precisely track the angular displacement. The high angle accuracy of ±0.1° is achieved through the high resolution and calibration of these displacement sensors. The instrument's microcontroller reads the signal from the displacement sensor and converts it into a direct reading of the bending angle.
 

2. Strain Gauge Force Transduction:

The bending force exerted by the material resisting the bending motion is detected by a strain gauge load cell. This type of transducer consists of strain gauges (thin resistive elements) bonded to a flexible metal element. As the bending force acts on the load cell, the metal element deforms slightly, causing a change in the electrical resistance of the strain gauges. This change in resistance is proportional to the applied force. A Wheatstone bridge circuit is typically used to convert the small resistance changes into a measurable voltage signal. The high sensing accuracy of 0.1% is a testament to the quality and calibration of the load cell and the associated signal conditioning electronics.
 

3. Closed-Loop Servo Control System:

To ensure precise control over the angular speed of the bending arm, the instrument often employs a closed-loop servo control system. This system uses feedback from an angular velocity sensor (e.g., an encoder coupled to the motor driving the bending arm) to continuously monitor and adjust the motor's speed. By comparing the actual speed to the set speed (0.5 to 5°/sec adjustable), the control system makes real-time adjustments to maintain the desired bending rate, ensuring consistent and accurate testing.
 

4. Linear Displacement for Sample Deflection (Related to Stiffness):

While the primary output is bending stiffness (force per unit deflection or angle), the instrument also implicitly measures the linear displacement or deflection of the sample at the point where the bending force is applied. This deflection is directly related to the bending angle and the test span. The instrument's internal calculations use the measured force and the resulting deflection (or angle) to determine the bending stiffness according to the principles of beam bending mechanics.
 

5. Data Acquisition and Processing:

The signals from the force sensor and the displacement sensor are continuously acquired and processed by the instrument's microcomputer system. This system performs signal conditioning, analog-to-digital conversion, and applies calibration factors to obtain accurate readings of force and angle. The microcomputer then calculates the bending stiffness based on these measured values and the set test parameters (sample size, test spacing).
 

6. Touch Screen Interface and Data Output:

The 7-inch touch screen interface provides a user-friendly way to set test parameters (vertical/horizontal direction, tension, speed, angle, spacing) and view the real-time measurements of force and angle. The instrument also features standard computer signal output for optional connection to a PC for more detailed data analysis and storage. The integrated thermal printer allows for immediate printing of test reports.
 

In essence, the ZY-TDY300 microcomputer bending stiffness tester utilizes precise displacement measurement for angle determination, strain gauge force transduction for accurate force detection, a closed-loop servo system for controlled bending speed, and sophisticated data acquisition and processing to provide a reliable and comprehensive assessment of the bending stiffness of flexible materials.