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RTD Probes with Mounting Threads and M12 Connectors

Vibration Resistant Platinum RTD (PT100) Sensor with M12 Connector and Mounting Thread


Item# PR-21A-3-100-A-1/4-0600-M12-1

Volume discounts available
Volume Discount Schedule
Quantity Price each
1-4 $121.24
5-9 $115.18
10-24 $112.75
25-49 $107.90
50-99 $105.48
100+ $103.05

In stock

Lead Time (If not in stock): 6 weeks
Vibration Resistant Platinum RTD (PT100) Sensor with M12 Connector and Mounting Thread PR-21A-3-100-A-1/4-0600-M12-1 PR-21A-3-100-A-1/4-0600-M12-1
  • Integral 4-Pin M12 A-Coded Male Connector for Easy Installation. An M12 Extension Cable is Required for Installation.
  • Available With a Variety 316L SST Threaded and Non-Threaded Housings
  • Pt100 or Pt1000 Class A, 4-Wire Platinum RTD Elements per IEC60751 Standard
  • Available with 1/4', 1/8', 6mm and 3mm Probe Diameters and a Wide Variety of Standard Lengths

PR-21A-3-100-A-1/4-0600-M12-1 Model Options

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Edit these specs to order a different model. Not all combinations are valid. Options compatible with previous selections will be in bold.

*Highlighted options are not compatible. Please select a different combination.

Process Temperature Range
Sensor Application
Process Connection Size
Nominal Output
Probe Diameter
Probe Length
Additional Feature
Number of Wires
Sheath Material
Termination Connection Type

See our New Higher Temperature, Bendable RTD Sensors at PR-26

Note: These Sensors Require an M12 Extension Cable to Connect the Sensor To Your Instrumentation. A Partial List Of Our M12 Extension Cables is Included in the Ordering Table Below.

Our RTD sensors with M12 connections provide for easy and efficient installation or removal of these sensors for periodic calibration, troubleshooting or replacement. Gone are the days of having to pull extension cables from cable trays in order to calibrate or replace the sensor, now you simply disconnect the sensor from the extension cable saving cost and downtime. The Omega PR-21 RTD is a flexible and robust temperature sensor constructed with 316L Stainless Steel housings and sheaths for strength and corrosion resistance. These sensors include a 4-pin, M12 A-Coded plug connector for easy assembly to patch cables or extension cables, as well as a variety of 'NPT' pipe thread and metric mounting thread options for easy installation into a wide variety of threaded ports. A non-threaded housing option is also available for other types of installations.

For use in thermowells, the PR-21SL Spring-Loaded version of this sensor is the preferred solution. The PR-21SL design includes a non-threaded PR-21A style probe with a self-gripping spring and 1/2NPT threaded fitting to insure that the probe will contact the bottom of the thermowell bore without damaging the sensor. This insures that the sensor length will always be a perfect fit for your thermowell. See the PR-21SL page for additional information.

The mounting thread options on the PR-21 Series sensors allow them to be used in a wide variety of applications, including:
  • Stand alone immersion sensors.
  • Installed directly into your product or process using an existing NPT or metric threaded port.
  • When combined with our M12-Handle, non-threaded 'A' style PR-21 probes can be used in hand-held sensing applications.
  • Other applications using a variety of available compression fittings or other accessories.

  • These RTD sensors can be used in any 2, 3 or 4-wire application by selecting one of the two available wiring arrangements (see the wiring diagrams below) and using only those wires needed for your measurement connection. This allows for simplified, trouble free installation with any existing application. This also allows the PR-21 series sensor to be used for a wide variety of replacement applications since it can be connected as-is with just about any measurement or control equipment available when combined with a 4-pin female M12 connector extension or patch cable.


    When ordering your PR-21 sensor, don't forget your extension cable. Omega offers a wide selection of extension cables including over molded PVC, Polyurethane and Silicone cables, as well as customized cables in a variety of materials with optional stainless steel braid or hose for improved mechanical protection, and a wide selection of instrument connections.

    Connect your PR-21 RTD sensor to one or more of Omega's wide variety of in-stock controllers, data loggers, transmitters, hand held thermometers, PLCs, or other measurement & control products to complete your measurement or control system. Omega offers a selection of programmable and fixed range transmitters that can be connected directly to the M12 connection of your PR-21 sensor. There are also wireless transmitter options available.

  • Metal Parts: 316L Stainless Steel Sheath and Housing.
  • Connector: 4-Pin 'A'-Coded M12 Plug Connector
  • Standard Mounting Threads: 1/2NPT, 3/8NPT, 1/4NPT, M10x1mm, M8x1mm, G1/4 BSPP, G1/2 BSPP and Non-Threaded
  • Standard Probe Diameters: 1/4', 1/8', 6mm and 3mm
  • Standard Probe Lengths: 6' for 1/4' & 1/8' Diameters, 160, 260 & 360mm for 6mm and 3mm Diameters
  • Sensor: Pt100 (100 Ohms at 0°C, .00385 TCR (alpha)) Standard, Pt1000 and Other Options Available
  • Accuracy: Class A Standard (per IEC 60751), Others Available Upon Request
  • Temperature Range: -50 to 250°C Except for the Connector Which is 85°C Max
  • Insulation Resistance: 100 Megohms Minimum at 100VDC at Room Ambient
  • Response Time: 3 Seconds Max (63.2% Response) When Immersed in Water Flowing at 3 feet/sec
  • Vibration Resistance: 10g's from 10 to 500Hz per MIL-STD-202G, Method 204D, Test Condition A (6' long or shorter)

  • loading all models
    loading all reviews
    Rated 5 out of 5 by from Direct Replacements These RTD's have great build quality and work well. They are offered in multiple wiring schemes, allowing them to be used as direct replacements parts for products like Meriam MDT500 integrated laminar flow element devices.
    Date published: 2023-04-06
    Rated 5 out of 5 by from rtd great quality, very accurate, and the quick disconnect feature makes swapping them out a breeze.
    Date published: 2021-06-21
    Rated 4 out of 5 by from Good RTD Good sensor overall. The shaft can be sealed to <10E-5 TorrL/s helium with an 1/8 inch Swagelok bored through tube fitting. Be careful not to bend the shaft though, the 1/8 inch is pretty delicate. Omega's mating cable is also pretty good but I wish they offered a shielded version with a metal connector.
    Date published: 2020-05-22
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    Could this be used in a flow apparatus to measure temps from -40F-140F with an accuracy of 0.5% full scale?

    Asked by: Pipeline Engineer
    Thank you for your inquiry Pipeline Engineer. Yes you can use this sensor to measure the temperature of the flow stream. This probe has an accuracy of Class A = &plusmn;(0.15 + 0.002*t)&deg;C or 100.00 &plusmn;0.06 O at 0&ordm;C. Here is the link for more information about the accuracy of a Class A RTD:
    Answered by: Application Engineer MC
    Date published: 2022-09-19

    Okay I saw the option 1 &amp; 2 diagram that but where&rsquo;s pin 1, 2, 3 &amp; 4 on the probe located. If only hooking up a 3 wire probe what wire do I not connect. Sorry not much information on the datasheet.

    Asked by: Debbie
    On the datasheet wiring diagrams you can see that 2 wires are common on each side of the PT100 symbol. If you only have a 3 wire input instrument you can just leave one wire from either side unconnected. If you are unsure you can always measure point to point on the wire to make sure the PT100 is located correctly per your instruments wiring diagram.
    Answered by: ANBENG
    Date published: 2020-04-03

    What is the pressure rating for the 1/2&quot; NPT probe?

    Asked by: ray1
    Thank you for you inquiry. Unfortunately this device doesn't have pressure rating.
    Answered by: CB Engineer
    Date published: 2020-11-16

    I'm looking at the product details for this probe; Vibration Resistant Platinum RTD (PT100) Sensor with M12 Connector and Mounting Thread, Item# PR-21B-3-100-A-1/4-1200-M12-1. And can't find the wiring diagram for it

    Asked by: Debbie
    If you click on Datasheet(PDF) under the bullets on the product page there is a wiring diagram for both available options.
    Answered by: ANBENG
    Date published: 2020-04-01

    What is the resistance of the RTD at its temperature extremes? What is the temperature coefficient?

    Asked by: Anonymous
    Thank you for your inquiry Anonymous. The resistance of this RTD at any temperature is 100 ohms. The alpha value for a Pt100 RTD like the PR-21D-3-100-A-1/8-0600-M12-1 is 0.00385.
    Answered by: Application Engineer MC
    Date published: 2022-09-19

    How I can represent this product PR-21A-3-100-A-1/8-0475-M12-1 as a AutoCAD drawing? Especially there are 4 pin, Could you name it please?

    Asked by: Andre
    Omega does not provide CAD drawings of it's products so send a request to to see if any dimensions of the probe needs to be discussed in greater detail.
    Answered by: Applications Engineer ANB
    Date published: 2022-07-25

    Can these be used without a thermowell using compression fittings? What would the pressure rating be for that type of application?

    Asked by: Alex U
    You can use a Compression fitting to seal the PR-21 series into a process however Omega does not specify a pressure rating.
    Answered by: ANBENG
    Date published: 2020-04-01
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