Hi

I have some problems about concept of DPDT or DPST switch.

I think if I have a DPDT level switch I can send two different set point signals (e.g. 300 mm and 500 mm of a vessel) to two different systems (e.g. DCS and ESD)? Is my opinion correct?

In addition, I think if I have a DPST level switch I can send signals related to 2 different set points to just one system.

It will be appreciated if help me.

 

The "P" stands for "pole" and refers to an associated set of output contacts on the switch, relay, etc.

The "T" stands for "throw" and is the number of output selections there are PER POLE.

So "DPDT" means "Double Pole, Double Throw". Two isolated circuits can be switched, each to two possible destinations.

"DPST" means "Double Pole, Single Throw". Two independent circuits may still be switched, but they can only be connected to one single remote location, or disconnected.

Two caveats:

A higher order switch can operate in the mode of a lower switch. For example, if you wire only the common and NO terminals of a SPDT relay, it now performs the function of a SPST unit and,

When I say "input" and "output" that should be taken loosely. There's no reason you can't use a Double [or more] Throw switch to SELECT a signal from multiple possible sources and feed it to a single point, rather than to take a single signal and REDIRECT it.

 

thank you very much Steve

I understood concept of DPDT and DPST but I didn't understand its application in process switches!!!

I mean that I want to know for example if I can send two different set point signals of a level switch to two different systems (about DPDT)or DPDT switch can only send one switch point???...

Saeid

 

>I mean that I want to know for example
>if I can send two different set point
>signals of a level switch to two
>different systems (about DPDT)or DPDT
>switch can only send one switch
>point???...

To answer that, you will need to find the specification of the switch. There are devices which have independent setting for the 2 poles, but most do not. (Independent settings are more expensive, but they are still cheaper than 2 separate switches.)

So, find the manufacturer and model number and Google it if you don't have a spec sheet on site.