Spectrophotometers are a kind of photometers that are used to find the amount of substance in the solution. Spectrophotometers detect the amount of radiation that is not absorbed by the solution in the sample chamber and gives information about the amount of substance in the sample. Spectrophotometers are used in many different fields such as chemistry, medicine, geology, environmental engineering and agriculture. Samples that will directly affect people, such as wastewater, drinking water, pharmaceuticals, are analyzed with high accuracy and possible hazards are avoided. In this study, a device that can be used in the detection of Salmonella bacteria is modeled. In addition, the fact that the heater unit of the device is on the test mechanism eliminates the need for heating in the external environment and the test data can be saved in the cloud environment over the internet connection, which is the novelty of this study. A spectrophotometer device was developed using Raspberry Pi 3 and Python software language. A 470 nm optical filter was used in the device. In addition to the features of standard spectrophotometers, the heating feature that can keep the sample temperature at the desired value has been added. This feature has been developed using the on-off logic method. Linear regression of optical measurements, R2 value was calculated as 0.9982 in density tests between 0.1 gram and 0.2 gram. The device was developed with a Raspberry Pi 3 minicomputer, it does not need an external computer for use. Thanks to the internet connection ability of Raspberry Pi 3, the analysis results are transferred to the cloud environment, allowing the user to see the results even when they are not at the device.