Strain Gage conditioner
Schematic
List of components:
List of components:
faceplate.cdr: CorelDRAW 9.0 file used to make faceplates
This module is a wheatstone
bridge amplifier. It is used to amplify the output voltage of the torque transducer
across pins D and E of the cannon receptacle.The 2B31J strain gage conditioner
is is an instrumentation amplifier, followed by a low-pass filter,
and an adjustable transducer excitation. The gain of the module is set to
approximately 2000 since the gain is defined as:
G=(1+94K ohm / Rg)*(20K ohm / (Rf+16.2K ohm))
where Rf is a fine span adjustable resistor inside the module with a max of 10K ohm and Rg is 50 ohms. The offset of the input signal can be adjusted by varying the OFFSET trim pot. This would be used if a certain torque level needs to be set as a baseline level. The torques generated at the ankle are usually lower than 100 Nm. Therefore, the input voltages from the torque transducer are below 0.3 mVolts. The ouptut voltages are then amplified by a factor of approximately 2000.
The frequency response of this module shows a gain of 66 dB (approximately 2000) in the pass-band region. The cutoff frequency is at 2K Hz and the roll-off is 20dB/decade. The phase shifts 180 degrees in the pass-band region and about 120 degrees at the cutoff frequency.
The output to 0 volt noise is as follows:
Last Modified: May 2, 2001 Laura Galiana