Understanding Spectrophotometer (USB) Devices

What is USB?

USB stands for Universal Serial Bus, and is one of (maybe the?) the most widely used interfaces for connecting (peripheral) devices to computers. It was designed as a way to make it much easier to connect peripheral devices to your computer. Some cool things it does: self identifies and (sometimes) will draw power from the computer to power your device. The USB standard itself is maintained by the USB-IF (USB Implementers Forum) and must pass a compliance test. There are different speeds as well: low-speed (USB 1.0/1.5 Mbps), full-speed (USB 1.0/12 Mbps), high-speed (USB 2.0/480 Mbps), and SuperSpeed (USB 3.0/5+ Gbps).

I would like to break down what is meant by the term “Universal Serial Bus.” The “universal” aspect relates to the fact that it is easy to use on pretty much any computer, ie. “plug-and-play.” The “serial” aspect is the concept of a “serial port” which indicates that it is a serial communication interface that means there is a transfer of information in or out, sequentially, one bit at a time. The “bus” aspect can actually be thought of in the same way as bus for public transport (at least abstractly): it “picks up” and “drops off” data from one location to another at a regular interval (in this case, refer to the speeds mentioned above).

Pinout of USB Type-A — Pinout and specification of USB Type-A. Source: ModDIY.

References: Serial port (Wikipedia) · USB communications (Wikipedia) · Beagle protocol analyzer manual (Total Phase) · Bus (Computer Hope) · USB connectors and pinouts (ModDIY)

What is a spectrophotometer?

On a fundamental level, each substance absorbs or transmits light over a specific range of wavelength. Spectrophotometry is a method used to measure how much a substance absorbs light by measuring the intensity of light that has passed through the substance. It can be used for a variety of purposes, but here, we are using this to understand the qualities of photographic paper art. Our spectrophotometer device measures light in the visible range (400-700 nm) of the electromagnetic radiation spectrum. Ours is a handheld device, which is most common in the graphics industry.

Diagram of fundamentals of spectrophotometer. — Single-beam scanning spectrophotometer. Source: Wikipedia, Spectrophotometry.

Table of the visible spectrum. — Wavelength, frequency, and photon energy of visible light spectrum colors. Source: Wikipedia, Visible spectrum.

References: Spectrophotometry (LibreTexts) · Spectrophotometry (Wikipedia) · Visible spectrum (Wikipedia)