Operation frequencies of traditional metamaterial absorbers are fixed meaning that it is not possible to change that frequency after the fabrication. Therefore, more studies are focused on the design of Tunable metamaterial absorber (TMA) since it is important to expand operation frequency. If the impedance of one or more layers of an absorber can be changed according to the applied electrical optical signal, then it would be possible to realize tunable absorbing designs. However, TMA studies reported previously are mainly focused on absorbing mechanism at microwave frequencies. In this study, TMA with varactor diode is designed and analyzed for absorber and sensor configurations. TMA is constructed by using a simple rectangular-shape geometry having two splits and a varactor diode placed at the right split. Numerical and experimental results show that perfect absorption is achieved when 0-10 V reverse bias voltage is applied. Resonance frequency can be easily tuned by changing the reverse bias voltage. Frequency dependent absorption behavior of TMA is presented with respect to different incident angles for TE and TM polarizations. A sensor application, knowing the absorption resonance frequency can provide the ability to determine the temperature of materials. The novelty of the study is to determine the temperature or the other parameters such as humidity or pressure by using TMA. It is also possible to determine the material type or its density if limited resource such as frequency generator is present.