Powder processing operations such as blending or pneumatic transport can potentially induce triboelectric charging with subsequent agglomeration. Traditionally the charging behavior is investigated using a Faraday cage. In this paper, an alternative nonintrusive probe connected to a voltmeter for comparative triboelectric charging studies of sieved pharmaceutically relevant materials such as alpha-lactose monohydrate (ALM) and adipic acid (AA) on acetal surfaces under controlled environmental conditions was explored. The probe was verified using standard voltages with determination in the positioning limits for effective measurements between probe and surface. Results obtained with the probe were found to be in good agreement with the Faraday cage method. A greater incidence of particle-to-wall adhesions in smaller sized AA particles led to a reduction in initial surface specific potential while the higher quantity of fines in the ALM larger sieve fractions could be the major contributing factor in the reduced surface specific potential.