What sensor should be used to measure scanning laser beams, such as bar code scanners?

For scanning low-level beams, such as bar code scanners, the Ophir special photodiode sensor model BC20 is the recommended choice. With scanning or moving beams the PD300 sensor, which is intended for stationary beam measurement, will not work properly. The key feature of the BC20 is the peak hold capability that the PD300 does not offer. Below is a simplified diagram of the BC20 circuitry that provides this unique scanning beam measurement capability.