Customers will sometimes ask "Why do ASG PG series LVDTs use a screw-clamp terminal block inside a condulet instead of a connector?" The answer is that, as a rule, a well-designed terminal block can produce a more reliable termination than a mated connector and is typically easier to install in a power plant, which is the primary application for PG series LVDTs. The 1/2“ conduit port easily accommodates rigid conduit, flexible conduit, liquid-tite and sealtite conduits, armored cable, and all types of cord grips.
It is well recognized that connectors are the highest failure items in any electronic hardware installation. However, sometimes users may have specific reasons for desiring a male connector that is sufficiently reliable for their proposed application. There are several choices for connectors that can be inserted into the 1/2 -14 NPT female conduit port adapter that is factory-installed in the condulet's 3/4” bottom port.
1. Turck makes two industrial grade 6-pin minifast® receptacles with a 1/2-14 NPSM male thread that can be inserted into the condulet adapter. However they are only rated to 105 C (220° F). The part numbers are RSF 61-0.3M for the standard and RSF 68-0.3M for the heavy duty version. These part numbers are for stock 0.3 m (12 in.) lead versions, which the user will have to shorten. A 6-pin connector means the user must remove the jumper between terminals B and C in the terminal block. If the application only needs 4 or 5 connections from the LVDT, Turck also offers suitable 4- or 5- pin minifast® connectors but the user would have to maintain in place the internal jumper between terminals B and C. Turck also offers a variety of standard molded cordsets up to 10-m (33 feet) long for either of these connectors, in both straight and right-angle termination versions, but they too are only rated for 105 C.
2. Another way to provide separable connections is to insert a cord grip into the condulet port adapter, and use an in-line connector set, particularly molded cordsets as noted above. If the application needs the full temperature capabilities of PG series LVDTs, then the cord grip, the connecting cable, and the connectors should be rated for 175 C (350°F) minimum. An aluminum cord grip with a 1/2-14 NPT male thread is available from Remke as p/n RSR-1004-H for 0.19 to 0.25 inch cable diameters, RSR-1005-H for 0.25 to 0.31 inch cable diameters, and RSR-1006-H for 0.31 to 0.38 inch cable diameters. All of these cord grips use a silicone rubber bushing rated for the PG series LVDTs' full 175 C temperature range.
3. A third way to install a connector rated for the full temperature capabilities of a PG series LVDT is to utilize a MIL-DTL 26482 type 2 receptacle attached to a MIL cable adapter from Glenair, Inc., specifically an Amphenol MS3471-W10-06P receptacle threaded into a Glenair 330-AS003B1004-5 thread adapter. This 6-pin receptacle is rated for 200 C, which exceeds the temperature rating of all PG series LVDTs. The mating connector is an Amphenol MS3476-W10-06S plug with a 97-3057-1004 cable clamp. Note that the cable used with the mating plug must also have a 200 C rating, and that practically all MIL-DTL connectors have equivalent commercial designations that are well known to MIL connector distributors.
The foregoing are merely a few ways to attach a connector to ASG's PG series of heavy duty AC-LVDTs. ASG does not offer these variants to the commercial market, but users are free to apply these solutions.
Although there are many other constructs possible, the key question is: Why not use the terminal block? A follow-up question is: Have you looked at ASG's LA-27 series of LVDTs with connector terminations? The standard version is built with the Turck 6-pin minifast® receptacle. There is a version with the same specifications and ratings as the PG series, including its temperature rating, that provides a separable connection. Another version is available with the high temperature cord grip and a user-specified length of high temperature 6-conductor (3x24 AWG STP) cable that typically runs to a junction box located away from the hot area in the immediate vicinity of the steam turbine by the user. So, while ASG does offer some LVDTs for the power gen industry with alternative connection arrangements to the terminal block in a condulet, a majority of the industry still prefers ASG’s PG series LVDTs to maximize reliability.