Recorders – Thermal recording
Patent
1986-09-11
1988-09-27
Paschall, M. H.
Recorders
Thermal recording
219216, 219486, 324542, 340640, 340655, G01D 1800, G01R 19145
Patent
active
047745266
ABSTRACT:
A thermal printer with a fault detection circuit for detecting faults in heating elements of the printer includes a print head containing heating elements and a heating circuit for each heating element and a power supply for supplying power to the heating elements. Power is supplied to the print head either directly through one terminal of the power supply or indirectly, during a test mode, through a fault detection circuit which is also connected to the print head. The fault detection circuit includes a constant voltage source, preferably formed of series-connected diodes, through which power flows to the print head. Current passing through the constant voltage source activates a photocoupler having an output the voltage of which determines whether a current is or is not flowing into the print head. A CPU which controls overall operations in the printer monitors the photocoupler and selects either a normal printing mode or a print head test mode. In the test mode, the CPU enables sequentially each of the heating circuits to determine their functional integrity.
REFERENCES:
patent: 4207517 (1980-06-01), Bloxam
patent: 4220912 (1980-09-01), Williams
patent: 4500893 (1985-02-01), Sakura et al.
patent: 4573058 (1986-02-01), Brooks
patent: 4595935 (1986-06-01), Brooks et al.
Kabushiki Kaisha Sato
Paschall M. H.
Williams H. L.
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