What is the reasoning behind the arrows on the circuit symbols of NTC (up and down arrow) and PTC (two up arrows)?

enter image description here

  • 2
    \$\begingroup\$ Can you add a picture? \$\endgroup\$ – MCG Feb 21 '19 at 10:18
  • \$\begingroup\$ I added the picture from the answer below. \$\endgroup\$ – user1583209 Feb 21 '19 at 22:20

I've never thought about it, but I think that the arrows describes how the thermistor behaves.

NTC: internal resistance decreases with a rise in temperature.

PTC: internal resistance increases when the temperature rises.

So, the first arrow represents the temperature and the second one the internal resistance.

enter image description here

  • \$\begingroup\$ Well, technically, either arrow can represent either thing, as long as one is temperature and the other is resistance ;) \$\endgroup\$ – DKNguyen Feb 21 '19 at 22:21
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    \$\begingroup\$ @Toor not true for the NTC picture. The left arrow on that must be temperature and the right hand arrow must be how the resistance reacts to temperature change. Otherwise the diagram is incorrect. \$\endgroup\$ – MCG Feb 22 '19 at 11:15
  • \$\begingroup\$ Logically untrue. If resistance falls as temperature rises, then that also means that resistance MUST rise as temperature falls.What's important is they move on opposite directions relative to each other, not the particular direction any one variable is being moved so it doesn't matter which arrow is which. The implication in your statement just now was the NTCs can only ever decrease in resistance which we both know is false. \$\endgroup\$ – DKNguyen Feb 22 '19 at 14:58

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