Measurements can be broadly classified into two categories: Static Measurements and Dynamic Measurements.
Dynamic measurements vary greatly over a short period of time (e.g., Vibration (Acceleration), Audio (Sound pressure), etc.). In these types of signals, we are mainly interested in the high frequency components so measurements down to DC are typically not necessary. For these measurements, we would use the AC input mode (or IEPE) which comes with a 0.375 Hz High Pass Filter. In most cases, the user sets another high pass filter to eliminate the low frequency components that are not needed. Crystal Instruments Spider-80X and Spider-80Xi systems are best suited for these types of applications.
Static measurements involve measuring slowly varying quantities such as temperature, humidity, etc. The data rate of these signals is typically 10 Hz or lower. It is critical that DC input mode is used to capture these signals without a high pass filter. Some measurement quantities such as Strain, Pressure, and Displacement could fall into either static or dynamic measurement categories based on the application. Most of sensors that measure these types of signals require precision excitation voltage. The sensitivity of these sensors, such as strain gage based sensors for example, vary depending on the excitation voltage given to the sensor. So, it is extremely important to precisely excite the sensors to obtain accurate results. To address the usability for a wide range of applications, Crystal Instruments developed the Spider-80SG/SGi which measures not only static and dynamic strain but is also capable of measuring static and dynamic measurements where a precision excitation voltage is needed.
We got our hands on a Rod End Load Cell from PCB (model 1381-04A) that is normally used to measure torque in kilo-pound-force (kLbf) and kilo-Newton (kN). This sensor is a strain gage based sensor with sensitivity defined with respect to the excitation voltage. In other words, its sensitivity has a linear relationship with excitation voltage. Higher sensitivity is available with higher excitation voltage. Because of this nature, the excitation voltage must be within narrow tolerance. The Spider-80SG and Spider-80SGi comes with user-defined precision excitation capability. With this feature, our Spider is capable of taking precision measurements from these Rod End Load Cell sensors and other sensors similar to this sensor.
This capability greatly expands the usability of Spider-80SG and Spider-80SGi to a wide range of applications and a wide range of measurement quantities.