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If I wanted to draw say a verical thermistor in a circuit diagram, it can look like any one of these four:

enter image description here

Is there a convention for which one to pick, or are all of them valid in any situation where a vertical thermistor is drawn?

Thanks

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  • \$\begingroup\$ If you don't get a good answer here in a few days, you may want to try Electrical Engineering \$\endgroup\$
    – Kyle Kanos
    May 11, 2015 at 19:11
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    \$\begingroup\$ If someone suddenly asked me what that symbol meant, I would guess that that's a photoresistor rather than a thermistor. \$\endgroup\$ May 11, 2015 at 19:35

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None of those look like a thermistor symbol to me. The usual schematic symbol looks like this:

enter image description here

or this:

enter image description here

Depending on whether the origin of the schematic is US/Asia or Europe respectively.

Edit:

Since it's an LDR- no the direction the light is coming from does not normally make a difference to the understandability of the schematic. It's a schematic, not a pictorial diagram. However, in the case where there is a light source closely coupled to the LDR which is part of the same schematic, it's common to show them together as below:

http://4.bp.blogspot.com/-n6zFBtshAEQ/TaTpT1kuJ_I/AAAAAAAAAW4/V91kFNkF-AU/s1600/smoke-detector-circuit.gif

The symbol shown in the above schematic is the one most commonly used in North America and Asia. The European symbol appears to be more like yours.

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  • \$\begingroup\$ Thanks, I got the name mixed up with an LDR. But I would ask the same question: Is there a convention or do you just draw it anyway you want. \$\endgroup\$
    – user45220
    May 11, 2015 at 19:55
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You can draw any circuit symbol in any rotation or mirroring, but IME each symbol has a more-or-less standard orientation, that mostly coincides with 'information flows from left to right" and "current flows from top to bottom".

In the case of an LDR (that is waht you seem to mean) the light is first so the most common convention (again, IME) is to have the arrows at the left side (your top two symbols).

Of these two, the left one looks more familiar to me (maybe because light is supposed to come from above?).

But again, it is not strictly wrong to use any of the other orientations (or to rotate them 90 degrees).

And IME I see LDRs more often without the circle/ellips around the resistor rectangle.

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  • \$\begingroup\$ If you make them horizontal, light is coming from above. \$\endgroup\$ May 11, 2015 at 20:32
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You have a light dependent resistor. Resistance changes as light changes.

enter image description here

There is no ambiguity in your symbols. It just the rotation/mirroring of the symbol via different schematic packages. It is common.

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