Terry Woods
Member
- Join Date
- Apr 2002
- Posts
- 3,170
Consider the following...
(this text added by PHIL to fix formatting of main page.this text added by PHIL to fix formatting of main page.
this text added by PHIL to fix formatting of main page. Sorry Terry it was a board glitch)
On the Left, Machine-A (from the OEM) is providing power to drive a relay.
In the upper section, the relay is resident in the Customer’s Machine (Machine-B).
In the lower section, the relay is resident in the OEM’s Machine (Machine-A).
On the Right, Machine-B (from the Customer) is providing power to drive a relay.
In the upper section, the relay is resident in the OEM’s Machine (Machine-A).
In the lower section, the relay is resident in the Customer’s Machine (Machine-B).
A design spec might call for the OEM to "Provide a set of WET Contacts", or "Provide a set of DRY Contacts" for the Customer. Or, the spec might call for the Customer to “Provide a set of WET Contacts", or "Provide a set of DRY Contacts" for the OEM.
Looking back to my military days, the phrases "Feet DRY" and "Feet WET" had some significance.
To say "Feet DRY" meant that an aircraft had reached land-fall. That is, it was no longer over the "WET" part of the trip and was now over the "DRY" part.
"Feet WET" was used, on the return flight, to indicate that the aircraft was no longer over “DRY” land and was now over the "WET" part of the return trip.
The same type of terminology is used for control systems, whether PLC type or plain-old ordinary relay type. There is a difference though... the difference is in the "Relative" usage of the terms.
If we assume that the space between Machine-A and Machine-B is an ocean (or, at least, extremely wet, as I have seen in some of the worse places I've worked) then the phrases make sense.
If, as the drawing indicates, Machine-A is from an OEM and Machine-B is an existing machine at the customer site, then, we have four physical possibilities.
OEM to provide “DRY” Contact for the Customer:
The OEM provides wiring and power to drive a relay in the Customer’s Machine. The OEM gets "Feet-WET" when his wiring leaves his control cabinet. The Customer has access to a set of contacts, controlled by the OEM, while keeping his “Feet-DRY”. The customer wiring does not leave the control cabinet. The OEM might or might not actually provide the relay.
OEM to provide “WET” Contact for the Customer:
The OEM provides a relay and a set of contacts, for the Customer, in the OEM’s Machine. The Customer gets "Feet-WET" when he, the Customer, provides wiring to the set of contacts residing in the OEM’s Machine. In this case, the OEM typically provides the relay. The Customer’s wiring goes “Feet-WET” when it leaves his control cabinet.
Customer to provide “DRY” Contact for the OEM:
The Customer provides wiring and power to drive a relay in the OEM’s Machine. The Customer gets "Feet-WET" when his wiring leaves his control cabinet. The OEM has access to a set of contacts, controlled by the Customer, while keeping his “Feet-DRY”. The OEM wiring does not leave the control cabinet. The OEM typically provides the relay.
Customer to provide “WET” Contact for the OEM:
The Customer provides a relay and a set of contacts, for the OEM, in the Customer’s Machine. The OEM gets "Feet-WET" when he, the OEM, provides wiring to the set of contacts residing in the Customer’s Machine. In this case, the Customer typically provides the relay. The OEM’s wiring goes “Feet-WET” when it leaves his control cabinet.
(this text added by PHIL to fix formatting of main page.this text added by PHIL to fix formatting of main page.
this text added by PHIL to fix formatting of main page. Sorry Terry it was a board glitch)
On the Left, Machine-A (from the OEM) is providing power to drive a relay.
In the upper section, the relay is resident in the Customer’s Machine (Machine-B).
In the lower section, the relay is resident in the OEM’s Machine (Machine-A).
On the Right, Machine-B (from the Customer) is providing power to drive a relay.
In the upper section, the relay is resident in the OEM’s Machine (Machine-A).
In the lower section, the relay is resident in the Customer’s Machine (Machine-B).
A design spec might call for the OEM to "Provide a set of WET Contacts", or "Provide a set of DRY Contacts" for the Customer. Or, the spec might call for the Customer to “Provide a set of WET Contacts", or "Provide a set of DRY Contacts" for the OEM.
Looking back to my military days, the phrases "Feet DRY" and "Feet WET" had some significance.
To say "Feet DRY" meant that an aircraft had reached land-fall. That is, it was no longer over the "WET" part of the trip and was now over the "DRY" part.
"Feet WET" was used, on the return flight, to indicate that the aircraft was no longer over “DRY” land and was now over the "WET" part of the return trip.
The same type of terminology is used for control systems, whether PLC type or plain-old ordinary relay type. There is a difference though... the difference is in the "Relative" usage of the terms.
If we assume that the space between Machine-A and Machine-B is an ocean (or, at least, extremely wet, as I have seen in some of the worse places I've worked) then the phrases make sense.
If, as the drawing indicates, Machine-A is from an OEM and Machine-B is an existing machine at the customer site, then, we have four physical possibilities.
OEM to provide “DRY” Contact for the Customer:
The OEM provides wiring and power to drive a relay in the Customer’s Machine. The OEM gets "Feet-WET" when his wiring leaves his control cabinet. The Customer has access to a set of contacts, controlled by the OEM, while keeping his “Feet-DRY”. The customer wiring does not leave the control cabinet. The OEM might or might not actually provide the relay.
OEM to provide “WET” Contact for the Customer:
The OEM provides a relay and a set of contacts, for the Customer, in the OEM’s Machine. The Customer gets "Feet-WET" when he, the Customer, provides wiring to the set of contacts residing in the OEM’s Machine. In this case, the OEM typically provides the relay. The Customer’s wiring goes “Feet-WET” when it leaves his control cabinet.
Customer to provide “DRY” Contact for the OEM:
The Customer provides wiring and power to drive a relay in the OEM’s Machine. The Customer gets "Feet-WET" when his wiring leaves his control cabinet. The OEM has access to a set of contacts, controlled by the Customer, while keeping his “Feet-DRY”. The OEM wiring does not leave the control cabinet. The OEM typically provides the relay.
Customer to provide “WET” Contact for the OEM:
The Customer provides a relay and a set of contacts, for the OEM, in the Customer’s Machine. The OEM gets "Feet-WET" when he, the OEM, provides wiring to the set of contacts residing in the Customer’s Machine. In this case, the Customer typically provides the relay. The OEM’s wiring goes “Feet-WET” when it leaves his control cabinet.
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