Proper use of ground conductor disconnect terminal blocks

Hi all,

This is a newbie question: what is the proper use of a Disconnect and ground conductor disconnect terminal block?

I've read that these terminal blocks are very helpful in testing analog i/o cards. Are there any other uses? What is the proper way to wire them?

For instance, if I have a 4 ch analog input card, would I use one terminal block for each channel? Or just one at the incoming vdc fron the power supply? The model I have comes as 2 terminal blocks joined by a jumper. It appears that the positive and negative connect at one end... Any tips for best use of these terminal blocks?

Below is a picture of the terminal block I'm talking about:


Thanks in advance!

although you can use these terminals, they are specifically designed for supply voltage and not analogue control.
please pst the link to the site so I can look further

I got that idea from a post about testing an analog card. Someone mentioned a similar terminal block on the third reply.

Hmm, I can't really find a direct link to the specs. The model is a "Wago 2006-1671/1000-0848", but most of the explanation about what is for is in the catalog; which I have posted a screenshot from here:



As you can see, it does mention there, that is used in both "control and process measurement", so I assumed they were referring to testing analog signals, but I could be wrong...

What do you think?

Having a way to connect your meter in series with a 4-20mA loop without ever breaking power is the only reason I can think of to use these. You put your meter in parallel first, then open the disconnect (or fused holder) and then current will flow through your meter for measurement.

Soooo.... 2 different answers then... I think. iant you said that it cannot be used for analog control and OkiePC says it can...

I've taken them apart to show what they look like inside, to see if it reveals anything that might give a definite answer as to their use. Here are the pics:



Sooo. what do you think? What I don't get is the little connection diagram on the left. Does it say to connect + and - on one end and then to ground on the other side? Btw, what does "PE", "R" and "G" mean? "Physical Earth", "Red" and "Green"?

But then the jumper joins the conductors on the other side in what it appears to close the circuit (if I'm connecting the negative on the other end), but I'm assuming that's what the diode is for? being reversed on one of the halves of the terminals so it won't let current get through the other end? I'm I really way off here??? How does one wire this block? Can anyone give me some tips?

Thanks!!!

PE would be ground - physical earth makes sense.

I think the specific type of terminals you are showing are designed for proximity switch connections.

I use disconnect terminals on all my analog signal field connections, but a simple single pole disconnect or fused disconnect only. That way you can put your meter probes on each screw, pull the disconnect and get a reading without disturbing the circuit to the I/O or whatever, reconnect, and you are all set.

Hmm, it doesn't say anything that specific in the catalog. But I guess I could connect just the half with the disconnect blade on the positive and use it for that purpose.

Now, do you use one of these for each analog channel or one for all?

Thanks!

Soooo, has anyone out there used a terminal block like this??? How did you wire it?

Thanks!

iant said:

although you can use these terminals, they are specifically designed for supply voltage and not analogue control.
please pst the link to the site so I can look further

Click to expand...

Just FYI
I said Can Use
not Cannot

but normally not needed - if you want to it is up to you.
the only time you need to test is when there is a problem.
be carefull you dont introduce a problem by having a future low current resistive point with that terminal strip

I am a firm believer, where possible, that Analogue cables should not be broken at any point.
I accept that you can not always do this.

PE stands for protective earth

I was hoping someone had use one of these specific disconnect blocks, but I appreciate all the answers and tips.

Thanks!

@ The OP

You can use knife disconnect blocks for analogs if you wish and I have done it many times without issue on current signals but I would be more concerned on voltage signals but it all depends on many things. There is no single right answer as it depend s on you project / aplication and needs. Signal type and distace are large factos to consider.

This is the best way to test analogs without breaking the circuit and usning special terminal blocks IMHO. http://www.fluke.com/Fluke/usen/Cla...mp-Process-Clamp-Meter.htm?PID=69415&trck=771

As others have pointed out the more junctions there are the more possible points of failure there are. Add in junction points with moving parts like knife disconnects and this increases but this may be acceptable risk and practice again depending on your application and needs. For you the convenience may outweith the risk.

One place that I do like to use knife disconnects is with ac coils /solenoids and if there is a issue I can use the knife disconnect blocks to remove a shorted coil from the circuit and isolate the coils neutral from the neutral common bar for resistance tests,etc and I use them frequently for this purpose as they work well for our application.

Just remember in this industry there is no one size fits all on anything.

@the PLC KID
I have had the pleasure of usig that Fluke meter - it is excellent.
I kept telling the boss it was mine but had to give it back to him.

I hate being Honest:beerchug:

I know, it looks pretty awesome! I had an opportunity to get my hands on a Fluke 789, so I got that one, but I'm gonna get a 773 as soon as I get a chance!

Thanks everyone!