Electrostatic Furniture Discharge Event Rates for Metallic-Covered, Floor-Standing Information Processing Machines

Electrostatic discharge (ESD) event rates were measured for a sample of metallic-covered, floorstanding information processing machines. Monitoring was done during periods of low humidity when the maximum electrostatic charges on people and furniture would naturally occur. The results are given in terms of events per machine per 8-hour shift as a function of a reference furniture waveform. With knowledge of the machine error response to ESD events, the event rate information can be used to estimate error rates of machines. INTRODUCTION Low impedance Electrostatic Discharge (ESD) of furniture is a major contributor to electromagnetic (EM) stress on electronic equipment. The random charging and subsequent abrupt discharging of office furniture often occurs unnoticed by the people in­ volved. If the discharge point happens to be the cover of a sensitive machine, unexplained errors may occur on a random basis that are recorded in system logs as "no trouble found." In addition, rather remote dis­ charges occurring to unrelated equipment may also contribute to errors of even greater perplexity. The association of equipment power and input/output cables may be such that common propagation paths are provided for the ESD impulse. metallic, "conductive" floors and humidity control involving 10 sites, 11 machines and 3360 shifts (one shift is defined as an 8-hour operating period). (2) The carpeted office or terminal room with little or no humidity control involving 8 sites, 8 machines and 282 shifts. Measurements were made on floor-standing, metallic-covered machines during periods of normally high static generation in the northeast and midwest.