Medical Oxygen Sensor Connector Types
When you remove a failed oxygen sensor from a ventilator or anesthesia workstation, the connector on it may not be one you recognize. Medical oxygen sensors use several connector types, from flat contact rings on the sensor body to small plugs on a cable, and the replacement has to connect the same way as the original.
To identify a medical oxygen sensor connector, check its shape and note whether it sits on the sensor body or on a cable, then confirm it on the sensor’s datasheet. This guide will show you how to recognize each common connector type and what else has to match.
Common Medical Oxygen Sensor Connector Types
Medical oxygen sensors, also called O2 cells, don’t share one standard connector. The table below covers six common types, with what each one looks like.
| Connector type | How it looks |
|---|---|
| Slip rings | Flat, gold-colored metal rings on one end of the sensor, with no plug or cable |
| 3-pin Molex | Small, white, rectangular plastic connector with three pins in a row, on a circuit board on top of the sensor |
| 3.5 mm mono jack or plug | Round socket on the sensor, or a round plug on a cable, the same size as a headphone connector |
| 4P4C modular jack | Small rectangular socket for a clip-in plug, the size used on telephone handset cords |
| 6P4C modular jack | A wider clip-in socket, with six positions and four contacts |
| Wired leads with a plug | Two loose wires from a circuit board on top of the sensor, each ending in a single-pin plug |
1. Slip Rings
Slip rings are flat, gold-colored metal rings set into one end of the sensor, around a central opening. The rings are the electrical contacts, so a slip-ring sensor has no plug or cable. They sit inside a raised rim on the housing, one ring inside the other, with a non-metal band between them. When the sensor is fitted in its holder, contacts in the equipment touch the rings and pick up the signal.
2. 3-Pin Molex Connectors
A 3-pin Molex connector is a small, white, rectangular plastic connector with three metal pins in a single row. On an O2 cell, it connects to a small circuit board on top of the sensor. One side of the housing has a raised ramp, which lets the mating plug fit only one way round.
Connectors of this style come in several families, each with its own spacing between the pins, called pitch. Two 3-pin connectors from different families can look similar and still not mate. To confirm the right one, check the sensor specified in your equipment’s instructions for use (IFU), or look up your equipment in a compatibility list.
3. 3.5 mm Mono Jacks and Phone Plugs
A 3.5 mm mono plug is a slim, round metal pin the size of a headphone plug, set in a black grip at the end of a cable that runs from the top of the sensor. Some sensors have the matching round socket, called a 3.5 mm mono jack, built into the sensor body instead.
“Mono” means the plug carries one signal. It still needs two metal sections, a tip for the signal and a sleeve for the return path, separated by one dark insulating ring. A stereo plug carries two signals, so it has three metal sections and two rings.
4. 4P4C and 6P4C Modular Jacks
A modular jack is a small, black, rectangular socket set into the top of the sensor, which takes a clip-in plug, the same style used on telephone cords. Inside the opening, a row of thin gold contacts runs along one edge.
The code in the jack’s name gives two numbers: the positions in the socket and the contacts actually fitted. A 4P4C jack has four positions and four contacts, the size used on telephone handset cords. A 6P4C jack is wider, with six positions but only four contacts fitted, so the two outer positions stay empty.
5. Wired Leads and PCB Plugs
Some sensors have two loose wires instead of a connector on the body. The wires, one black and one white, are joined to a small printed circuit board (PCB) on top of the sensor, and each wire ends in its own single-pin plug. Each plug connects to a matching contact inside the equipment, so the wire length also has to be long enough to reach it.
6. Less Common Connectors
A few medical oxygen sensors use connectors outside the common types. There are three you may come across:
-
Four-pin male socket: four exposed metal pins on the sensor body
-
Straight miniature power jack: a small round socket, similar to those used for DC power
-
Two-way Mate-N-Lok: a rectangular two-contact connector made by TE Connectivity
These connectors are harder to match by eye, so the model and part number on the sensor’s label are the safest way to confirm them.
How to Identify the Connector on Your O2 Cell
You can identify most O2 cell connectors by eye, with the sensor in your hand, then confirm the match with the part number on its label. Check these three things:
-
Shape: flat rings, a round socket or plug, or a rectangular connector
-
Contacts: the number of rings, pins, or metal sections on a plug
-
Mounting: whether the connector sits on the sensor body or at the end of a cable or wires
These checks narrow the connector down to one of the common types, but a visual match doesn’t always confirm the exact version. Some sensor models come in versions with different connectors, so read the model and part number from the sensor’s label and look them up in a compatibility list. If the label is worn, the equipment’s IFU or service manual names the specified sensor.
Does the Same Connector Mean the Sensor Will Fit?
Not always. A matching connector tells you the sensor will plug into the equipment, but it doesn’t tell you whether the sensor sends the right signal or fits in its holder. Two more things have to match:
-
Output signal: whether the sensor sends a voltage in millivolts (mV) or a current in microamps (µA), and its output range in room air. A sensor with the wrong output can plug in and still give an incorrect oxygen reading or fail calibration.
-
Housing: the size, shape, and mounting of the sensor body, so the sensor seats correctly in its holder.
A compatibility list already accounts for both, because it pairs each equipment model with a sensor whose connector, output, and housing match. You can look up your equipment in our compatibility list to find that sensor directly.
Read more: How to Choose the Right Medical Oxygen Sensor for Your Equipment
Start With Your Equipment Model
If the connector on your sensor doesn’t match any type above, or its label is unreadable, the equipment it came from can still lead you to the right replacement. At NRC Pure, we match each of our medical oxygen sensors to specific equipment models, so knowing your equipment narrows the search to the sensor built for it.
You can find those matches in our compatibility list by searching for your equipment’s manufacturer and model. If you’re still unsure after checking the list, contact us with your equipment details, and we’ll help you find the matching sensor.
Frequently Asked Questions
Can I Use an Adapter to Fit a Different Connector?
No. An adapter or a rewired connector changes the electrical path the equipment was designed for and can affect the oxygen reading. Use a sensor whose connector matches your equipment, and have qualified personnel install it as the equipment’s IFU describes.
Can a Damaged Connector Cause a Low Oxygen Reading?
It can. Corrosion, bent pins, or a loose fit can interrupt the contact or add resistance to a signal of only a few millivolts. The result may be a low or unstable reading, or a calibration error. Inspect the equipment-side contacts when you replace the sensor, because a new sensor won’t fix a damaged socket.
Is the Connector Part of the Sensor or the Equipment?
Both sides have a part. The sensor carries its own half, such as slip rings, a jack, or a plug on a cable, and the equipment carries the matching half. When you replace the sensor, its half of the connection is replaced with it, and the equipment’s half stays in place.
