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.