Systems and methods for continuous mode force testing
Described herein is a method and system for testing a force or strain sensor in a continuous fashion. The method employs a sensor, a test fixture, a load cell, a mechanical actuator and tester hardware and software to simultaneously record signal outputs from the sensor and load cell as functions of time. The method provides time synchronization events for recording data streams between, for example, a linear ramp of the force on, or displacement of, the sensor and for extracting performance characteristics from the data in post-test processing.
1. A testing system, comprising:
a test fixture configured to include electrical connection to a force or strain sensor;
a mechanical actuator configured to apply a force to the force or strain sensor;
a load cell configured to measure an amount of the force applied to the force or strain sensor;
a controller configured to operate the mechanical actuator and simultaneously record respective output signals from the force or strain sensor and the load cell;
wherein simultaneously recording the respective output signals from the force or strain sensor and the load cell comprises sampling the respective output signals in a burst mode, wherein the burst mode is defined by a sampling frequency and a sampling period;
wherein the respective output signals from the force or strain sensor is sampled with a first sampling frequency and a first sampling period; and
wherein the respective output signals from the load cell is sampled with a second sampling frequency and a second sampling period, wherein the first sampling frequency is different than the second sampling frequency.
2. The testing system of claim 1 , wherein the force or strain sensor comprises one or more piezoresistive, piezoelectric, or capacitive transducers.
3. The testing system of claim 1 , further comprising a robotic arm, wherein the mechanical actuator is controlled by the robotic arm.
4. The testing system of claim 3 , wherein the robotic arm is operably connected to and controlled by the controller.
5. The testing system of claim 1 , wherein the respective output signals recorded by the controller are stored in a memory of the controller.
6. The testing system of claim 1 , wherein the respective output signals from the force or strain sensor and the load cell are recorded as a function of time.
7. The testing system of claim 1 , wherein the controller is configured to operate the mechanical actuator to continuously change the amount of the force applied by the mechanical actuator from a first force value to a second force value, wherein the first and second force values are different.
8. The testing system of claim 7 , wherein the controller is further configured to:
hold the first force value constant while recording the respective output signals from the force or strain sensor and the load cell as a function of time;
subsequently ramp the first force value to the second force value while recording the respective output signals from the force or strain sensor and the load cell as the function of time; and
hold the second force value constant while recording the respective output signals from the force or strain sensor and the load cell as the function of time.
9. The testing system of 8 , wherein the controller is further configured to use a transition from the first force value to a ramped force and a transition from the ramped force to the second force value as temporal data synchronization points between the respective output signals from the force or strain sensor and the load cell.
10. A testing system, comprising:
a test fixture configured to include electrical connection to a force or strain sensor;
a mechanical actuator configured to apply a force to the force or strain sensor;
a load cell configured to measure an amount of the force applied to the force or strain sensor;
a controller configured to operate the mechanical actuator and simultaneously record respective output signals from the force or strain sensor and the load cell, simultaneously recording the respective output signals from the force or strain sensor and the load cell comprises sampling the respective output signals in a burst mode, wherein the burst mode is defined by a sampling frequency and a sampling period, the respective output signals from the force or strain sensor is sampled with a first sampling frequency and a first sampling period, the respective output signals from the load cell is sampled with a second sampling frequency and a second sampling period, and the first sampling frequency is different than the second sampling frequency; and
a robotic arm, wherein the mechanical actuator is controlled by the robotic arm.
11. The testing system of claim 10 , wherein the controller is configured to operate the mechanical actuator to continuously change the amount of the force applied by the mechanical actuator from a first force value to a second force value, wherein the first and second force values are different.
12. The testing system of claim 11 , wherein the controller is further configured to:
hold the first force value constant while recording the respective output signals from the force or strain sensor and the load cell as a function of time;
subsequently ramp the first force value to the second force value while recording the respective output signals from the force or strain sensor and the load cell as the function of time; and
hold the second force value constant while recording the respective output signals from the force or strain sensor and the load cell as the function of time.
13. A method for testing a force or strain sensor, comprising:
connecting the force or strain sensor to a test fixture, wherein the test fixture is configured to include electrical connection to the force or strain sensor;
operating a mechanical actuator to apply a force to the force or strain sensor;
simultaneously recording respective output signals from the force or strain sensor and a load cell, wherein the load cell is configured to measure an amount of the force applied to the force or strain sensor;
wherein simultaneously recording the respective output signals from the force or strain sensor and the load cell comprises sampling the respective output signals in a burst mode, wherein the burst mode is defined by a sampling frequency and a sampling period;
wherein the respective output signals from the force or strain sensor is sampled with a first sampling frequency and a first sampling period; and
wherein the respective output signals from the load cell is sampled with a second sampling frequency and a second sampling period, the first sampling period is different than the second sampling period.