Abstract—The accuracy of the vibration measurements is directly related to testing equipment. There are some reasons that affect the performance of instruments like sensitivity, internal noise level, temperature, pressure etc. The influence of instruments should be considered in vibration recordings. There are too many products on the market. For the researchers, the main struggle is to decide which sensors or digitizers or their combinations should be used for the defined study aim or the equipment which they have is suitable or not for their purpose of the study. There are limited studies in this field in the literature. In this study, three different sensors were compared in the frequency domain, a seismometer and two different accelerometers. The seismometer is Guralp CMG-6TD (G6), one of the accelerometers is Guralp CMG-5TCDE (G5) and the other one is TDG Sensebox-7021 (TDG). The measurements were conducted in a four-story, residential reinforced concrete (RC) frame building. G6 and G5, G5 and TDG were compared to each other in two different measurements. As a result of this study, in all comparisons, the first mode’s frequencies were very close to each other and the frequency spectrums which established by means of the compared instruments were quite similar to each other.