Lock-In AmplifierLock-in Amplifier for myRIO

This application uses the myRIO-1900 to implement a lock-in amplifier in the FPGA. The application measures a modulated signal and a reference signal, which can also be generated with myRIO. The lock-in amplifier can measure very low level input signals, even if they are buried in noise or are smaller than myRIO’s 12-bit resolution. The lock-in amplifier includes a selectable high-pass filter to remove any input DC offset, and also includes a programmable output low pass filter that removes any noise beyond the frequencies of interest. The application is geared towards education and understanding the principles of a lock-in amplifier. It includes extensive documentation and instructions for building a circuit to measure heart rate by using an LED and photodiode amplifier to measure the amount of light absorbed through the blood vessels in a finger.


Compatible With LabVIEW

Lock-in Amplifier Accessory for myRIO

This accessory is the fastest way to get started with the Lock-In Amplifier for myRIO add-on. The board includes a red LED to generate modulated light, and a photodiode and signal conditioning circuitry to measure the received signal. This accessory can be used for a variety of measurements, such as determining your heart rate. If you place your finger between the LED and photodiode, the Lock-In Amplifier will pick up the small difference in absorbed light as blood pumps in and out of the capillaries in your fingertip. The add-on uses this information to calculate heart rate. You can order the board with the configuration that best suits your measurements:

  1. LED and photodiode soldered on the board as shown in the image
  2. Loose LED and photodiode so you can attach them to your own fixture
  3. SMA Connectors for the reference output and 5V input signal.

If you would like a board with SMA connectors configured for current input, or for orders outside the US, please contact us at