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An astounding example of massive charge concentration is lightning. Air movements and clouds cause charge to built up until the attractive force is so great at that a bolt of lightning results. Less spectacular examples are sparks to door knobs, Scotch tape being attracted t6your'fiand, the TV star 'static cling,' and calculator disruption.
This Technical Note is concerned with calculator disruptions. EVERY calculator in a plastic case is prone to being disrupted bv a static discharge. When the machine is adversely affected by Electro Static Discharge, ESD, the result is a static crash. There are two kinds of crashes, hard and soft. A hard crash result in a hardware failure. A soft crash confuses the calculator's logic, often resulting in a locked-up keyboard or blank display. Most calculator designs are otected from ESD hard crashes. It is the soft crash that disrupts normal operation and erases darta that causes the most difficulties for calculator users.
High static conditions are an environment issues. When temperatures drop, and the air is dry, the normal rapid recombining of charges is slowed down. Moisture in the air normally keeps charges from building to troublesome levels. Air conditioned rooms and man-made materials used in carpets contribute to 'generating' charges.
Today's calculators use very low power circuits. The energy generated by walking across a carpet , will easily power a liquid crystal display. Static electricity provides more than enough energy to cause extraneous 'siginals' to be.injected into the calculator's logic system. The only way to keep the charges out of the machine is to seal it in a conductive she'll. Mianufacturers do not consider this practical for cost and style reasons so users must adjust to the problem. It is important to realize that the problem is environmental and that not all machines will be exposed to the same environmental and handling conditions. The static season is usually during the winter months.
Precautions can be taken during the static season to reduce static crashes. Here are a few suggestions.
When you experience strange calculator behavior a static crash should be suspected. Almost any behavior is possible and it is useless to describe and analyze what is happening. The corrective step is to reset the machine. Consult your owner's manual, usually in the service or warrantv section. Removing the batteries is a sure way of resetting the machine. HP-41 batteries need to'be out 36 to 48 hours. A master clear should be performed in anv way possible, such as using the backarrow-on sequence, on assigning STO c to a key using the PPC ROM, ZENROM, or kev assignment card. Some machines -mostly Japanese models- have a reset button on the back. Press with a paper clip to reset the machine.
Conclusion: every calculator or computer can experience a static crash and these days it is unusual for the crash to (hard crash) damage the equipment. Soft crashes cause behavior and the machine must be reset to known condition to insure proper behaviour and the machine must be reset to a known siar 9 operation. Precautions for getting through the static season are listed above. Some machines are more sensitive to static disruption than others of the same model. Applying a conductive coating on work surfaces, carrying cases, and the machine will greatly reduce static problems. Most users will not have problems, but the real world environment is constantly changing and you may experience a static crash. Unfortunatelv, most manufacturers won't even discuss the problem, and this Technical Note can only scratch the surface.