Why does ASG use a screw-clamp terminal block in PG series LVDTs instead of a connector?

Why does ASG use a screw-clamp terminal block in PG series LVDTs instead of a connector?

Customers will sometimes ask "Why does 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 area for PG series LVDTs. The conduit port easily accommodates rigid conduit, flexible conduit, liquid-tight and sealtite conduits, armored cable, and all types of cord grips.

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 condulet port adapter that is factory-installed in the condulet's bottom port:

1. Turck makes two industrial grade 6-pin minifast® receptacles with a 1/2-14 NPSM male thread that is 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, a suitable 4- or 5- pin connector could be used but the user would have to maintain in place the internal jumper between terminals B and C.)

Turck makes a variety of molded cordsets up to 10-m (33 feet) long for either of these connectors, but they also are only rated for 105 C (220° F).

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 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 which use a silicone rubber bushing rated for a PG series LVDT's 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? There is a version with the same specifications and ratings as the PG series, including its temperature rating, and provides a separable connection. Another version is available with the high temperature cord grip and a high temperature 6-conductor cable that typically goes to a junction box away from the turbine.