Sensors for National Instruments DAQ

Single Axis Goniometer

The flexibility of joints in the body can be determined by simple range of motion (ROM) tests. These ROM exercises can aid physical therapists, athletic trainers, and physicians when they are examining joint dysfunction. Athletes and individuals who participate in physical activities generally are classified as being flexible due to the fact that their joints function over wide ranges of movement. Good flexibility may improve body position and awareness, enhance athletic performance, and help prevent injuries during and soreness after exercise. A joint's range of motion is expressed as the number of degrees of rotation that occur when the joint goes from its starting position, which is usually full flexion, through its full range of motion to its end position, which is usually full extension. The most common device used to measure range of motion is the single-axis goniometer. Examples of the types of movements that can be measured include: flexion/extension/hyperextension, abduction/adduction, and plantar flexion and dorsiflexion.

The GNN-100 has two arms, one stationary and one moving, and a sensor which generates a voltage output which is proportional to the number of degrees of rotation that occur in the joint to which the goniometer is mounted. The stationary arm, which holds the sensor, is placed parallel to the stationary portion of the joint. The movable arm is placed along the moveable side of the joint. The axis of the goniometer is placed directly over the joint so that accurate measurements of the range of motion of the joint can be made along a single axis.

Input Range

45o to 180o

Output Range

-2V to 3.5V


Required for every use

Default scaling Value

180o = 3.43V                                                          

 90o = 0V                                                                  

 45o = -1.94

Calibration Instructions
1. Install the IX-ELVIS board into the National Instrument ELVIS platform or the IX-myDAQ board onto the NI myDAQ. If using ELVIS, connect the ELVIS power supply to the ELVIS unit and connect it to the computer via a USB cable. Ensure both of the power switches are in the “on” position. For the myDAQ, connect it to the computer using the USB cable.

2. Connect the MINI DIN7 connector of the GNN-100 to either CH1 or CH2 of either the IX-ELVIS or IX-myDAQ board.

3. Open the recording software, select the channel that the GNN-100 is connected to and ensure the range is set to +/-5V.

4. Use a textbook to set the GNN-100 to an angle of 90°, type 90 for the SP1 Angle and press set to record the voltage in SP1 Voltage.

5. Set the GNN-100 straight, enter '0' for SP2 Angle, and then press Se to record the voltage in SP2 Voltage.

Measurement Instructions
1. Follow the above calibration instruction.

2. Prepare the experiment and record.

*Note: The signal may be inverted if the IX-MYDAQ is used.
  • Model: GNN-100

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