Forces claimed by potential propellantless propulsion systems like the Mach-Effect-Thruster or the EMDrive are in the μN or even sub-μN range. In this paper, an automated thrust balance design capable of measuring forces of 100 nN for devices with a maximum mass of 10 kg is described to test these claims. The torsion balance features an electromagnetic calibration method, adjustable magnetic damping and tilt control as well as electromagnetic shielding. All onboard electronics can be controlled wirelessly via an infrared module for serial communication. Power is supplied to the balance using three separate liquid metal feedthroughs: one for voltages up to 500 V and frequencies up to 200 kHz, one for high voltage up to 30 kV DC or AC, and one for high frequency signals up to 3 GHz. The device can be rotated by 180° to measure three different thrust directions without breaking the vacuum and changing the setup in order to gain confidence and refute e.g. thermal drifts. The whole balance is controlled via a script language implemented in LabVIEW. We tested Mach-Effect-Thrusters provided by Woodward and our self-built model exploring higher frequencies and mixed-signals that are believed to create significantly higher forces. Also a magnetostrictive version was built and tested. For the EMDrive, several different frequencies and setups (with/without dielectric insert, flat/spherical end caps) were tested. Results of the tests performed between August and September 2018 are presented, but no final conclusions can be drawn.