I am having a lot of Diamond symbols in my schematic named as Pxxxx. I am not able to find what it means as there are no legends mentioned in the file.enter image description here

Also, are there any general conventions that govern the usage of symbols in schematics?

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    \$\begingroup\$ It's just a net label. \$\endgroup\$ – Eugene Sh. Aug 29 '16 at 14:02

Those look to me like testpoints. On an actual board they would either be empty pads or they may actually be testpoint components.

  • \$\begingroup\$ Are test points typically indicated using this symbol? \$\endgroup\$ – Soju T Varghese Aug 29 '16 at 14:08
  • \$\begingroup\$ As far as I know there is not much of a standard for test points. Usually I see them as little circles with a wire connecting to them (radio-electronics.com/images/…) though using other symbols is not unheard of. It generally comes down to how the design engineer was trained and his/her personal preferences. \$\endgroup\$ – DerStrom8 Aug 29 '16 at 14:10
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    \$\begingroup\$ @SojuTVarghese ours look differently (sort of a triangle) and are labeled TPxx. I guess it's a company wide standard but not much more. \$\endgroup\$ – Arsenal Aug 29 '16 at 14:11

I'll hazard a guess that these are test points. These provide an convenient access to a signal. Test points are useful for debugging, quality control testing, calibration, troubleshooting. A signal can be probed at a test point. Or, a test signal may be injected into a test point to exercise the downstream circuitry.

On the PCB, a test point can manifest itself differently, depending on the expected type of test.

  • It can be a throughole of surface-mount component for clipping a probe to.
  • It can be throughole for sticking an oscilloscope into.
  • It can be a surface-mount pad for automated test equipment.

As far as I know, there is no single standard schematic symbol for test points. Here are a few symbols that come with schematic software.

test point symbols from OrCAD schematic capture (from OrCAD)

enter image description here (from Altium)

The standard designator for test point it TP (source).


It's either a net label or a test point.

  • \$\begingroup\$ sorry, but i don't get what a net label is..? \$\endgroup\$ – Soju T Varghese Aug 29 '16 at 14:04
  • \$\begingroup\$ A net label is simply a way of naming a net (a connection). This is especially useful if the net has a special function and you want the reader to know what it does, or in CAD work it is used for error checking and for converting a schematic to a PCB design (showing where components connect) \$\endgroup\$ – DerStrom8 Aug 29 '16 at 14:06
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    \$\begingroup\$ A net label just assigns a name to that wire so it can be referred to later on another sheet, on reports, in simulation, during board layout, etc. \$\endgroup\$ – alex.forencich Aug 29 '16 at 14:06

The test points could document locations for probing on a bed of nails functional/ICT fixture defined by a Test Engineer working with the Design Engineer for high fault coverage for fixture design.


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