HP V8.5 manual Thermal Printhead, Automatic Head Temperature Feedback

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T H E O R Y O F O P E R A T I O N

5.4THERMAL PRINTHEAD

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The thermal printhead is comprised of a row of 1728 heater elements (nibs). Each bit within a scan addresses an individual nib. Plot patterns are generated one scan at a time, each scan consisting of a horizontal row of dots. A nib produces a dot if the corresponding scan bit in the buffer is a logic level “1”. Nibs in the printhead are heated, causing a thermo-chemical reaction with the coating on the media. The intensity or period for which the nib is heated is called the burn strobe.

Automatic Head Temperature Feedback

The thermal printhead rises in temperature as it plots images on paper, thus, less energy is required to activate each nib as the plot proceeds to create an image of the same intensity. A thermistor embedded in the head measures the head temperature and provides feedback information to the main logic board. The main logic board decreases the burn strobe accordingly to keep the contrast of the plotted image consistent as the plot proceeds.

If the printhead temperature reaches 60º C, the Automatic Head Temperature Feedback circuit stops the plotter in order to let the head cool down. The control panel display reads hot (Ht) and the error light flashes. When the thermistor measures that the printhead temperature has cooled to 45º C, the plot resumes with no loss of data.

V8.5eRev2.2.2002

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Contents V8.5 Thermal Plotter Trademarks Copyright NoticeDisclaimer HaftungsausschlussPage Iii V8.5eRev2.2.2002 Limitation of Liability Contents Operation Appendices MaintenanceV8.5eRev2.2.2002 Media Description General DescriptionAbout this Manual Operation FunctionalSpecification S Media Interface TransportElectrical Environmental PhysicalUnpacking InstallationMounting and Positioning Media Installation Interface SetupInstalling rolled paper Back Panel Roll paper and film path Opening the plotter Lid Installing fan-fold paper Installing rolled film Spindle blocks E R a T I O N Power Supply PrecautionsControl panel Using the Control PanelControl panel button functions Rev2.2.2002 Changing function settings Control Panel Functions and SettingsContrast Default SettingsTestplot Speed Media Scaling Form feed length Emulation vertical resolutionMenusettingsareF2, F4, F8, tF,PF E R a T I O N Bytes per scan Menusettingsare b1, b2, g1, g2, g3, and g4Grayscale media table number Setup headers for programming the V8.5eSA=4B E R a T I O N Byte Line feed Error MessagesFehlermeldungen Introduction Plotter Functions and FeaturesPower supplies T I O N Interface Interface timing and signalsStepper motor Data Transfer Clear Minimum data rates Data ratesScan width VerticalresolutionMode signals Print modeThermal Printhead Automatic Head Temperature FeedbackMedia Sensors Film mediaMaintenance I N T E N a N C E Maintenance GuidelinesRegular Maintenance Cleaning the thermal printhead Cleaningtheplatenroller Replacing the fuse Troubleshooting Plotter does not plot ProblemsPlotwithverticalwhitestripes Plot has vertical white stripesPlot is blotchy or faded Plot contrast is weak Plothasblackverticallines SolutionPaper is wrinkling or tearing along one edge Plot is wrong lengthCan’t make changes to control panel settings Plotter has no powerPlot output speed is erratic Bloomingplot Form feed does not stop at top-of-form marks Form feed stops before desired lengthSkewedplot Plot is skewed or unreadableR R a N T Y R R a N T Y C I I T a B L E S Interface Connector PIN Assignment TableB-2. Centronicscablepinoutsstraightthrough Centronics Interface Board Centronics Interface Board Centronics Interface Board