A difficulty in assessing the accuracy of both the blow-off tribo and charge spectrograph measurement techniques is that there are no standard developer samples that have calibrated charge values. The precision of both toner charge measurement techniques can be assessed by plotting the average q/d value from the charge spectrograph measurement versus the q/m value obtained from the blow-off tribo measurement of a common developer sample. Julien and Gutman have both published results showing the q/d value is proportional to the q/m value. From the slope of the line drawn through the data, the average particle radius of the toner in the developer can be calculated. We have found that this calculated value for the toner radius is nearly equal to the measured median toner radius obtained from a volume displacement particle size measurement. This independent measurement of the toner radius serves as a confirmation of the accuracy of the toner charge measurement techniques.
E. J. Gutman, "A Method to Confirm the Accuracy of the Blow-Off Tribo and Charge Spectrograph Measurement Techniques" in Proc. IS&T Int'l Conf. on Digital Printing Technologies (NIP18), 2002, pp 290 - 293, https://doi.org/10.2352/ISSN.2169-4451.2002.18.1.art00072_1