The heavy ion beam probe (HIBP) system on the Madison Symmetric Torus (MST) reversed field pinch (RFP) provides many unique opportunities to make measurements never before possible on an RFP. For the first time, particle transport induced by electrostatic field fluctuations in the core region of MST can be characterized through the simultaneous measurement of electron density fluctuations, electrostatic potential fluctuations, and their wavenumbers. A multiple entrance aperture Proca and Green type electrostatic energy analyzer will be used to measure plasma fluctuations at two or three nearby sample locations. Wavenumber information is derived from the phase shift between sample volumes. Initial experimental results of fluctuation measurements will be presented. Issues such as sweep plate calibration, wavenumber measurements, correlation between fluctuation signals, and particle transport due to fluctuations will be addressed.