  We formulate an entanglement criterion using Peres-Horodecki positive partial
transpose operations combined with the Schr\"odinger-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 $2\times 2$ (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.
