496 Digital Signal Processing Lock-in Amplifier
The 496 lock-in amplifier ADC is a key component of spectroradiometer systems operating in conditions where the optical signal to be measured may be confounded with a background optical signal, whether from ambient lighting, or, in the infrared, heat (or infrared radiation) emitted by instrumentation and the background.
To discriminate the two contributions, the optical signal to be measured is modulated on a known carrier wave by an optical chopper, the relative phase difference between these two waveforms must be taken account of.
In the 496, the input and reference are digitised prior to determination of the components in two orthogonal states in order to take the vector sum of the two. Phasing intervention, as is custom with traditional lock-in amplifier-based systems, is therefore not required.
The 496 module is housed within the 417/417T base unit.