The purpose of this knowledge base article is provide a simple visual guide to the common process connections found on Hamilton sensors.


The PG13,5 is the most common connector for Hamilton sensors. This metric straight thread connector relies on an o-ring around the sensor body to provide the seal against process pressure. While PG13,5 connectors have wrench flats, proper sealing is achieved at 2 Nm (18 inch-lb) which is approximately finger-tight. Sensors with PG13,5 connections may rely upon a separate sensor holder to mate with piping connections such as G1-1/4, TriClamp, and others.


NPT refers to National Pipe Thread. This is a tapered pipe thread commonly found in North America. Sensors that use NPT connections are designed to install directly into process piping thus no additional hardware is needed. NPT connections are common in industrial applications. Since the threads are tapered they are not suitable for hygienic applications. Look for NPT connections on the InchTrode pH sensor products.


This process connection is also sometimes referred to as an Ingold fitting. It uses a female threaded union nut to mate with a fixed socket welded to the bioreactor vessel. The seal between the sensor holder and the socket is created with the O-ring on the sensor body. The O-ring position for the holder should match the length of the socket. This creates a flush seal with the inner wall of the vessel and avoids any dead space where contamination might occur. G1-1/4 connections are uncommon on process sensors themselves. They are more typically found as part of the sensor holder such as our FlexiFit products.


TriClamp process connections rely on a tapered flange on the sensor holder. This flange mates with a similar tapered flange welded to a nozzle off the process vessel. A sanitary gasket is placed between the two flanges to form a seal. Finally, a mechanical clamp is tightened around both flanges to affix the holder in place. TriClamp connections come in different diameters typically ¾, 1½, and 2 inch. The flange size of the sensor holder much match the flange size on the vessel. TriClamp connectors on sensors are uncommon and only offered on certain conductivity sensors. They are more common with sensor holders used for mounting 12mm sensors into the process.

Less common sensor process connections

NEUMO BioControl

NEUMO is a German company that has designed many different sanitary connections. Their BioControl connection uses a bolt down flanged process connection with an O-ring seal around the internal lip of the flange to form a flush process connection. NEUMO BioControl connections are an option on the Conducell I inductive conductivity sensors.


The Varivent process connection is a flush flange connection. It is similar to the TriClamp connection in that it relies on a clamp to hold the flange of the sensor together with a matching flange on the process connection. Varivent connections use an o-ring seal around the internal diameter of the connection. Varivent connections are most commonly found in breweries, dairies and other food applications. They are sometimes known as Tuchenhagen connectors from the name of the company that invented them. Varivent connections can be found on certain Conducell I and the Conducell 4USF-VV products.

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