TP1-004

The TP1-004 is a 0.015" square resistive printing element mounted in a short cylindric barrel or tube to form a thermally printing The TP1-004 unit is intended to replace disposable ink cartridges or hot wire styli in multipoint and other similar analog recording systems. Because TP1-004 is capable of operating in the D.C. mode, the TP1 can provide a highly legible trace which can be held relatively uniform regardless of changes in chart speed or slew rate by use of a feedback system to control printing power versus relative writing speed. It may also be operated in the pulsed mode to print dashed traces without the necessity of pen lift-off mechanism due to its relatively low thermal time constant. The resistive printing element is covered by high temperature glass to resist abrasive wear effects of thermal paper. The pen should be slewed in the direction shown in mechanical outline dwg. no. TP.1-004 to minimize abrasive wear of the termination pads for the resistor element even though they are covered by the protective glass.

Since the thermal paper acts as a heatsink in removing heat from the printing element, the input power to the thermal pen must be controlled in direct proportion to the relative paper velocity and slew rate to avoid thermal damage of the pen, as well as to maintain a relatively constant trace width. Printing power must be experimentally determined by the user and is dependent on chart speed, slewing rate, and paper sensitivity. ln the case where it is desired to print dashed traces for identification purposes, it will be necessary to print with 5 msec or wider pulses, setting the off-time to obtain the desired dash spacing, and to vary pulse amplitude to control input power versus speed. ln all cases, the user of TP1-004 should lifetest for the combined effects of abrasive wear and thermal fatigue of the printing element under actual use conditions to determine acceptability due to the many variables involved.