SELECTION COMPARISON
Overview
NPN and PNP refer to the transistor type in the sensor output stage, which determines whether the signal is "pulled low" or "pulled high."
The direct consequence of wrong selection is: when the sensor is connected, the PLC cannot receive the signal, or the signal is always on.
The basis for judgment is not the sensor itself, but the wiring method of the PLC input terminal - the sensor must cooperate with the PLC, not the other way around.
comparison
| Comparison point | NPN (sinking type/Sinking) | PNP (Source type / Sourcing) |
|---|---|---|
| output switches when actuated | Connect the signal terminal to 0V (pull it low) | Terminate the signal to +V (pull high) |
| current flow | current flows into the sensor | Current flows from the sensor |
| Corresponding to PLC input | Input module with common termination +V | Input module with common terminal 0V |
| common markets | Japanese equipment, more common in Asian markets | European and American equipment and export machinery are more common |
| effect of incorrect wiring | The signal does not work or is always on | The signal does not work or is always on |
How to decide which one to choose
- First check whether the common terminal (COM) of the PLC input module is connected to 0V or +24V.
- If COM is connected to +24V, the input needs to be pulled low to operate - select NPN.
- If COM is connected to 0V, the input needs to be pulled high to operate - select PNP.
- If you are replacing an existing sensor, the safest way is to directly use the output type of the original model without changing it.
- If the equipment is to be exported to Europe and the United States, or if the customer clearly requires it, PNP is usually preferred.
Output correspondence of Omron common series
| Series | NPN model examples | PNP model examples | Notes |
|---|---|---|---|
| E3Z diffuse reflection | E3Z-D61 / E3Z-D62 | E3Z-D81 / E3Z-D82 | D61/D81 approximately 100mm, D62/D82 approximately 1m |
| E3Z shooting | E3Z-T61 / E3Z-T62 | E3Z-T81 / E3Z-T82 | T61/T81 approximately 15m, T62/T82 approximately 30m |
| E2E NEXT | Named with C in it | Named with B in it | B=PNP, C=NPN, and NO/NC are distinguished by wiring methods. |
Important: do not use a shortcut such as "suffix 1 means NPN and suffix 2 means PNP" to determine sensor output type.
Taking E3Z as an example, D61 and D62 are both NPN, and the difference lies in the detection distance; what really distinguishes the output is the ten-digit number.
The complete part number should be checked before purchasing.
Frequently Asked Questions
Will it burn out the sensor if I connect it wrongly?
In most cases there is no immediate damage, but the signal does not work properly. However, if incorrect wiring causes a short circuit in the power supply, there is still a risk of damage. It is recommended to confirm before wiring.
Can the same model support both NPN and PNP?
Some series have universal output models, but most standard models are fixed output types. When purchasing, confirm the complete part number and do not assume it is switchable.
How to confirm which sensor is the original one when replacing it?
Look at the original sensor nameplate for the complete part number, or for wiring colors and PLC input termination methods. You can send photos for us to assist with confirmation.
What else should I confirm besides NPN/PNP?
It is also necessary to confirm the detection mode (diffuse reflection/through beam/mirror reflection), detection distance, power supply voltage, output action mode (normally open/normally closed) and wiring form (pre-wired or connector).
Need help confirming a part number or application?
Send the complete part number, BOM, nameplate or product photos. Documents and images can be shared through WhatsApp, Telegram or WeChat.
