We formulate an entanglement criterion using Peres-Horodecki positive partial transpose operations combined with the Schrödinger-Robertson uncertainty relation. We show that any pure entangled bipartite and tripartite state can be detected by experimentally measuring mean values and variances of specific observables. Those observables must satisfy a specific condition in order to be used, and we show their general form in the 2 × 2 (two qubits) dimension case. The criterion is applied on a variety of physical systems including bipartite and multipartite mixed states and reveals itself to be stronger than the Bell inequalities and other criteria. The criterion also work on continuous variable cat states and angular momentum states of the radiation field.PACS numbers: 03.65. Ud, 03.67.Mn In the past few years, many criteria detecting entanglement in bipartite and multipartite systems have been developed [1]. The Peres-Horodecki positive partial transpose (PPT) criterion [2] has played a crucial role in the field and provides, in some cases, necessary and sufficient conditions to entanglement. That criteria is formulated in terms of the density operator and any practical application involves state tomography. Other criteria have been proposed so they could be tested experimentally in a direct manner, as the Bell inequalities [3,4] or the entanglement witnesses [5]. More recently, criteria based on variance measurements have been studied for continuous and discrete variable systems [6,7,8,9,10,11,12,13,14].In [11] the Heisenberg relation has been used along with the partial transpose operation to obtain a criterion detecting entanglement condition in bipartite nongaussian states. That idea was generalized in [13,14] with use of the Schrödinger-Robertson relation instead of the Heisenberg inequality. In this paper, we generalize completely those concepts and prove that the Schrödinger-Robertson type inequality is able to detect entanglement in any pure state of bipartite and tripartite systems. Experimentally, it can be realized by measuring mean values and variances of different observables; however we show that all observables are not suitable and we yield the general condition they must satisfy to be eligible. For 2 × 2 systems, we explicitly give their general form. The inequality has a wide application range : qubits, angular momentum states of harmonic oscillators, cat states, etc. For the mixed state case, the inequality detects entanglement of bipartite Werner states better than the Bell inequalities [3] and also leads to a good characterization of multipartite Werner states.For any observables A, B and any density operator ρ, the Schrödinger-Robertson uncertainty relation The Heisenberg uncertainty relation is obtained if the last term is not considered, which gives a weaker inequality.The PPT criterion [2] is a sufficient condition for entanglement, saying that if a bipartite state ρ is separable it can be written as ρ = i p i ρ 1 i ⊗ ρ 2 i with usual notations and its partial transpose ρ pt ≡ i p i ρ 1 ...