The 01MT-5B8 is a Belimo passive averaging temperature sensor with a Pt 1000 (1000Ω Platinum RTD, continuous sensing element) on a 50 ft (15 m) flexible probe. The probe is strung serpentine across the face of a coil, mixing box, or large duct cross-section so the controller reads a single true average temperature instead of a single-point reading from one location. Unlike multi-point averaging sensors that take readings at discrete points along the cable, the Pt 1000 element is continuous along the entire probe — every inch of the cable contributes to the reading, eliminating air stratification blind spots between sense points. The signal returns directly to the controller as a resistance — no 24V supply or signal conditioning required.
Defeating air stratification on cooling and heating coil discharge, mixed-air plenums, large supply and return ducts, AHU plenums where outdoor and return air have not yet mixed, and any application where a single-point sensor would give biased readings depending on where the probe was placed. Especially useful in freeze protection and economizer changeover, where cold spots near a coil edge should not be missed.
Key Features
Unlike multi-point averaging sensors that take discrete readings along the cable, the Pt 1000 element is continuous along the entire probe length. Every inch contributes to the reading — no blind spots between sense points.
UV-resistant orange polycarbonate enclosure with NBR70 seal. UL94 5VA flame class and UL 2043 plenum compliant for return-air ducts.
Bendable 50 ft (15 m) probe strings serpentine across coil faces and duct cross-sections without crimping or losing accuracy at the bend points.
Ships with the A-22D-A08 mounting kit (6 brackets) for clipping the probe into serpentine routing, plus the A-22D-A09 enclosure mounting plate and 1/2" NPT conduit adapter. No additional parts pull required.
Passive resistance returns directly to the controller — no 24V supply, no signal conditioning, no scaling required.
Pluggable terminal block accepts up to 2.5 mm² conductors. Block lifts out for bench-side wiring, then snaps back in.
Industry-leading factory warranty backed by Belimo's worldwide service network.
Technical Specifications
| Specification | Detail |
|---|---|
| Sensor Style | Flexible cable averaging temperature sensor — 50 ft probe |
| Measured Value | Temperature (averaged across probe length) |
| Sensing Element | Pt 1000 (1000Ω Platinum RTD, continuous sensing element) |
| Sensing Method | Continuous element along entire probe length |
| Measuring Range | -30...160°F [-35...70°C] |
| Fluid Temperature Range | -30...160°F [-35...70°C] |
| Probe Length | 50 ft [15 m] |
| Application | Air — across coil face or duct cross-section |
| Mounting | A-22D-A08 mounting kit (6 brackets, included) for serpentine routing of the probe; A-22D-A09 plate (included) for enclosure mounting |
| Cable Entry | 1/2" NPT conduit adapter included — cable gland with strain relief, ø6...8 mm |
| Electrical Connection | Pluggable spring-loaded terminal block, max 2.5 mm² |
| Housing | UV-resistant polycarbonate, orange — UL94 5VA |
| Enclosure Rating | NEMA 4X / IP65 (UL Enclosure Type 4X), UL 2043 plenum compliant |
| Protection Class | IEC/EN III, Protective Extra-Low Voltage (PELV) |
| UL 2043 Compliance | Suitable for use in air plenums per NEC 300.22(C) and IMC Section 602 |
| Time Constant τ (63%) | 100 s typical at 0 m/s air velocity |
| Power Required | None — passive resistance element |
| Weight | 0.55 lb [0.25 kg] |
| Manufacturer | Belimo |
| Manufacturer Part Number | 01MT-5B8 |
| Warranty | 5-year factory warranty |
What's In the Box
- 01MT averaging temperature sensor with 50 ft (15 m) flexible probe in orange UV-resistant housing
- A-22D-A08 mounting kit (6 brackets for serpentine probe routing)
- A-22D-A09 mounting plate (S-housing)
- 1/2" NPT conduit adapter
No additional probe brackets, mounting plates, or conduit fittings required for a standard install. Pluggable terminal block is part of the housing.
Documentation
Frequently Asked Questions
Does this need 24V power?
No. The 01MT-5B8 is a passive resistance temperature sensor — the controller reads its element directly through the analog input. No 24V supply or signal conditioner needed.
What sensing element is in the 01MT-5B8?
The 01MT-5B8 uses a Pt 1000 (1000Ω Platinum RTD, continuous sensing element). The letter after '01MT-5' identifies the element: B=Pt 1000, E=Ni 1000 (JCI), L=NTC 10K Type II, M=NTC 10K Type III (Precon), Q=NTC 20K. The trailing digit identifies probe length: 4=10 ft, 5=20 ft, 8=50 ft. Match the element to your controller's input curve.
What is an averaging sensor and when do I need one?
An averaging sensor uses a long flexible probe strung across the face of a coil or duct cross-section so that the reading reflects the true average temperature, not the value at one point. Single-point probes can read 10°F or more above or below the actual average if placed near a stratified pocket. Use averaging when reading mixed air, when controlling freeze protection across a coil face, or whenever the duct cross-section is large enough that placement of a single sensor would meaningfully bias the reading.
What does "continuous sensing element" mean for the Pt 1000?
Belimo's Pt 1000 averaging sensor uses a single platinum element that runs the entire length of the probe — every inch contributes to the resistance reading. This eliminates the gaps between sense points found on multi-point averaging sensors (which use 4-12 discrete elements connected in series or parallel). For applications where stratification might exist between sense points — narrow cold fingers off an OA intake, for example — the continuous element catches what a multi-point would miss.
How do I install the probe across a coil face or duct?
String the probe in a serpentine pattern across the duct cross-section, clipping it to the duct wall using the included A-22D-A08 brackets (6 supplied). Aim for roughly one foot of probe per square foot of duct cross-section, with the serpentine pattern covering the full face evenly. The enclosure mounts to the duct exterior using the included A-22D-A09 plate and routes into 1/2" NPT conduit via the included adapter.
What temperature range does the 01MT-5B8 handle?
Probe and cable jacket are rated -30 to 160°F (-30...160°F [-35...70°C]). Pt 1000 and Ni 1000 elements share this wider range. NTC variants of the 01MT have a narrower fluid temperature range of 30 to 120°F.
Does it work with my BAS?
Any BAS controller with a temperature input configured for the Pt 1000 curve will read this sensor directly. See the linked Resistance Characteristics PDF for the full curve table at standard temperature points.
How is this different from the 01DT duct sensor?
The 01DT is a single-point insertion probe — it reads temperature at one location in the duct. The 01MT averages temperature across the entire probe length, defeating stratification that would bias a single-point reading. Use 01DT for small ducts where the air is well-mixed; use 01MT for large ducts, mixing plenums, and any application where one location wouldn't represent the whole air stream.
- Sensor Type:
- Averaging
- Averaging Type:
- Flexible Cable
- Output Signal:
- Temperature Only
- Temperature Element:
- 1K Platinum RTD
- Probe Length:
- 50 Foot
- Sensing Method:
- Continuous Element
- Humidity Element:
- None
- CO2 Element:
- None
- VOC Element:
- None
- Display:
- No Display
- Setpoint:
- No Setpoint
- Override:
- No Override
- Supported Protocols:
- None
- Enclosure:
- NEMA 4X Enclosure
