Specifying and monitoring temporal requirements in Digital Twin (DT) systems is challenging, as writing formal specifications in temporal logic is often complex and inaccessible to domain experts. This typically necessitates close collaboration with software engineers, introducing communication overhead and slowing development. We present DTChecker, a reusable self-contained monitoring tool for DT systems built on RabbitMQ-based architectures. The tool enables domain experts to write temporal specifications in a browser-based editor with language server support. These specifications are automatically translated into Signal Temporal Logic (STL) formulas and evaluated in real-time on data streams from sensors or services. Robustness scores are streamed to a front-end dashboard to visualize how well the system satisfies the specified requirements over time. This enables domain experts to write and verify temporal properties easily, thereby improving the real-time monitoring of the DT. We demonstrate the tool through integration with an open-source incubator DT case study.
