What does it mean by NPN sensor & PNP sensor ?

[danishdeshmuk]

What does it mean by NPN sensor & PNP sensor ?

what's the difference between the two ?

How differently they're used in specific application ?

 

[mgate]

I'm not sure, but I think those are sensors that use a Bipolar junction transistor...
Probably they trigger a logic signal... I think the sensor sensing part should be connected to the base o a transistor NPN or PNP... And they are probably used as normal transistors

PNP	NPN

 

[FvM]

Your assumption is basically correct. The terms are describing the output polarity of sensors with digital logic output based on an output transistor in common emitter configuration. "PNP" refers to positive supply switching, "NPN" to ground switching. "PNP" is the output type needed to interface with industry standard PLCs.

 

[danishdeshmuk]

With the help of DMM, can we check whether the given sensor is NPN or PNP ?

---------- Post added at 19:04 ---------- Previous post was at 19:02 ----------

in terms of NPN & PNP sensor, what does it mean by load ? that is being shown in the images of NPN & PNP type sensors

 

[mgate]

in terms of NPN & PNP sensor, what does it mean by load ? that is being shown in the images of NPN & PNP type sensors

Load could be for example a relay, or the input of a microcontroller .. (although with the microcontroller you would need to use a a pull up or pull down resistor according to the type) ..

i.e. interface of a opto NPN sensor to microcontroller

**broken link removed**

 

[danishdeshmuk]

How to measure the correct output voltages of both the types whether npn or pnp if the output voltage is 24 Vdc ?

---------- Post added at 19:23 ---------- Previous post was at 19:13 ----------

would npn generate the positive output & pnp generate the negative output ? If yes, then , with what (which) reference ?

 

[mgate]

You can imagine it working as a switch...

when activated, NPN will allow current to flow from the collector to the emitter, meaning it will generate a negative output a the collector (because it will stay at the same potential of the emitter)...

when activated, PNP will allow current to flow from the emitter to the collector, meaning it will generate a positive output a the emitter (because it will stay at the same potential of the collector)...

Its somehow similar to a relay

 

[danishdeshmuk]

but to check whether its working fine or not, what should be the output voltages for npn & for pnp sensors ? and, where the DMM probes be connected to get the confirmation ?

if we connect DMM red probe to positive 24 VDc input supply to the sensor & common (black) probe to output wire then what should be the readings ?

 

[mgate]

In NPN.. If you put the common probe on the output, and the positive probe in the 24v supply, you should read 24v on the digital multimeter when its active..

In the PNP, if you put the common probe on the the negative source, and the positive probe on the output, you should get 24v when its active..

Although I'm not absolutely sure

 

[danishdeshmuk]

DMM would read +ve 24 Vdc in case of NPN & would read -ve 24Vdc in case of PNP by connecting as you recommended up there in the previous post ???

 

[mgate]

DMM would read +ve 24 Vdc in case of NPN & would read -ve 24Vdc in case of PNP by connecting as you recommended up there in the previous post ???

No .. the way I've described you well get +24DC on both cases

 

[danishdeshmuk]

if we reverse the checking set-up that you told , then, what would happen ?

 

[mgate]

what do you mean by reverse?... can you be more explicit?

 

[danishdeshmuk]

means if i have to check npn sensor & i checked its output voltage as if a pnp sensor ? And vice versa ......

 

[mgate]

well, if you check a PNP as if it was a NPN, or a NPN as if it was a PNP, you will get always 0v reading in the DMM , at least I think you will

 

[danishdeshmuk]

when i measure a PNP , Normally Closed (NC) sensor , on its output , when i connect the red (positive) probe of DMM to ground / common & negative (black) probe to output (black wire) the DMM showed -24 V dc ........ Is it the right way to test the PNP sensor with a DMM ?

 

[FvM]

Is it the right way to test the PNP sensor with a DMM ?

You are connecting the DMM to the right terminals, but why do you connect the instrument reversed with red cable to negative supply ground and black cable to positive output? Connecting it straight with black cable to ground makes more sense, isn't it?

 

[danishdeshmuk]

Re: What does it mean by NPN sensor & PNP sensor ?

so if i connect the Red Probe (positive) to the output (black wire) & common/ground probe to the negative / 0v (blue wire ) , then , on its output the PNP sensor would give 24 VDC ??? Am i right now & is the sequence of connecting the probes right too ?

- - - Updated - - -

And for the NPN one , the Red Probe (positive) to the positive 24 Vdc supply (brown wire) & common/ground probe to the output (white wire ) , then , on its output the PNP sensor would give 24 VDC or -24 VDC ??? Am i right now & is the sequence of connecting the probes right too ?

 

[FvM]

I would do as you said in both cases.