FEATURES
• Fast response time for rapid protection
• Automatic resetting once overload is removed
• Operates on DC or AC voltage
• UL approved types available (E148885)
• Material categorization:
for definitions of compliance please see
www.vishay.com/doc?99912

APPLICATIONS
Over-temperature/over-load protection for metering, low
current signal protection, digital signal protection against
over-voltage

DESCRIPTION
Test and measuring instruments, such as oscilloscopes and
digital multimeters, can be easily damaged if excessive
voltages are applied across their input terminals.
Simple and effective overload protection can be provided by
connecting a high-voltage PTC thermistor in series with the
instrument; see Typical Connection of the PTC Thermistor
for Digital Multimeter Protection drawing. Under normal
conditions, the resistance of the PTC thermistor is low, so
the test voltage will be measured by the instrument. Under
an overload condition, the PTC thermistor will switch to its
high-resistance state, absorbing the overload current and
protecting the instrument. When the overload is removed,
the PTC thermistor will return to its low-resistance state,
ready to resume its protective function.