About Selecting Temperature Sensors
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Bayonet-Mount Thermocouple Probes for Surfaces
Quick to install and remove, these probes won’t shake loose from a surface even in high-vibration environments. Twist their bayonet fitting into an adapter mounted on your surface to hold them in place. Their tip is exposed, so they can respond to rapid changes in surface temperatures but can’t be used in liquids. For accurate readings, move the fitting along the length of the cable until the tip of the probe is pressing firmly against the surface you’re measuring. To prevent wear, corrosion, and abrasion, an armored stainless steel cable protects the wiring that connects these probes to your temperature-monitoring device. This makes these probes a good choice for humid and harsh environments.
Pick the thermocouple type that best covers the temperature range you expect your surface to be. You should also make sure the thermocouple type you choose is compatible with the device you plan to connect it to. These probes are often used with temperature controllers and thermometers.
These probes are manufactured to conform to ASTM E230 for accuracy. Accuracy is how far off the reported value is from the actual temperature.
Choose a probe with spade or ring terminals if you plan to connect to a terminal block. For installation, note that the red wire lead is negative.




Probe | Cable | Wire | |||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Lg. | Dia. | Response Time, sec. | Max. Temp., °F | Accuracy | Probe Material | Sensor Type | Material | Max. Temp. °F | Lead Lg. | Gauge | 4 ft. Cable Lg. | 6 ft. Cable Lg. | 8 ft. Cable Lg. | 10 ft. Cable Lg. | |
Type J—Flat-Pin Mini Thermocouple Connector | |||||||||||||||
1/2" | 3/16" | 2.5 | 900° | ±4° F between 32° to 533° F ±0.75% above 533° F | 304 Stainless Steel | Grounded | Stainless Steel | 900° | __ | __ | 0000000 | ||||
Type J—Round-Pin Thermocouple Connector | |||||||||||||||
1/2" | 3/16" | 2.5 | 900° | ±4° F between 32° to 533° F ±0.75% above 533° F | 304 Stainless Steel | Grounded | Stainless Steel | 900° | __ | __ | 0000000 | ||||
Type J—Spade Terminals | |||||||||||||||
1/2" | 3/16" | Not Rated | 900° | ±4° F between 32° to 533° F ±0.75% above 533° F | 304 Stainless Steel | Ungrounded | Stainless Steel | 900° | 3" | 20 | 0000000 | ||||
1/2" | 3/16" | 2.5 | 900° | ±4° F between 32° to 533° F ±0.75% above 533° F | 304 Stainless Steel | Grounded | Stainless Steel | 900° | 3" | 20 | 0000000 | ||||
Type K—Flat-Pin Mini Thermocouple Connector | |||||||||||||||
1/2" | 3/16" | 2.5 | 900° | Not Rated below 32° F ±4° F between 32° to 533° F ±0.75% above 533° F | 304 Stainless Steel | Grounded | Stainless Steel | 900° | __ | __ | 0000000 | ||||
Type K—Round-Pin Thermocouple Connector | |||||||||||||||
1/2" | 3/16" | 2.5 | 900° | Not Rated below 32° F ±4° F between 32° to 533° F ±0.75% above 533° F | 304 Stainless Steel | Grounded | Stainless Steel | 900° | __ | __ | 0000000 | ||||
Type K—Spade Terminals | |||||||||||||||
1/2" | 3/16" | Not Rated | 900° | Not Rated below 32° F ±4° F between 32° to 533° F ±0.75% above 533° F | 304 Stainless Steel | Ungrounded | Stainless Steel | 900° | 3" | 20 | 0000000 | ||||
1/2" | 3/16" | 2.5 | 900° | Not Rated below 32° F ±4° F between 32° to 533° F ±0.75% above 533° F | 304 Stainless Steel | Grounded | Stainless Steel | 900° | 3" | 20 | 0000000 |
Magnetic Thermocouple Probes for Surfaces

Often used where it’d be difficult to mount a standard probe, these probes stick onto magnetic surfaces to take temperature readings. They have a magnet that holds them firmly in place on motors, bearings, and other surfaces. A spring behind the probe protects the cable from strain that could cause it to fray or break. Pick the thermocouple type that best covers the temperature range you expect your surface to be. You should also make sure the thermocouple type you choose is compatible with the devices you plan to connect it to. They’re often used with temperature controllers, thermometers, and other temperature-reading devices.
Probes with wire leads offer more flexibility than probes with connectors already attached because you can either wire them to a terminal block or add your own connector. For installation, note that the red wire is negative.
Spring-loaded probes help keep readings accurate by making sure the tip stays in constant contact with the surface you're measuring. These probes are manufactured to conform to ASTM E230 for accuracy. Accuracy is how far off the reported value is from the actual temperature.
Probe | Cable | Wire | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Lg. | Dia. | Movement | Response Time, min. | Max. Temp., °F | Accuracy | Sensor Type | Lg., ft. | Material | Max. Temp., °F | Lead Lg. | Gauge | Holding Force, lbs. | Each | |
Type J | ||||||||||||||
Wire Leads | ||||||||||||||
1/2" | 1" | Spring Loaded | Not Rated | 1000° | ±4° F between 32° to 533° F ±0.75% above 533° F | Exposed | 6 | Fiberglass | 1,000° | 1/4" | 24 | 16 | 0000000 | 0000000 |
Type K | ||||||||||||||
Wire Leads | ||||||||||||||
1/2" | 1" | Spring Loaded | Not Rated | 1000° | Not Rated below 32° F ±4° F between 32° to 533° F ±0.75% above 533° F | Exposed | 6 | Fiberglass | 1,000° | 1/4" | 24 | 16 | 0000000 | 000000 |