A method, apparatus, and computer program product in a data processing system for testing differential clock or oscillator signals. The method involves mixing a dispersion of particles in platelet form, a carrier fluid and a functionalizing agent which is distributed in the carrier fluid and has a proportion by mass in the dispersion corresponding to a predetermined mass ratio based on the proportion by mass of the particles. The gateway software includes device communications software for sending and receiving device messages to and from the one or more embedded devices and gateway communications software for sending and receiving communications to other software.