What it is

The Optris CTi 3M is a miniaturized two-piece infrared thermometer for non-contact temperature measurement of metal from 86 °F to 3,362 °F (30 °C to 1,850 °C). It measures in a short 2.3 µm spectral range, which reduces reading errors on materials with unknown emissivity. That makes it suited to metals, secondary metal processing, metal oxides, and ceramic materials. The sensing head is only 0.55 in (14 mm) in diameter and 1.10 in (28 mm) long. It runs up to 185 °F (85 °C) ambient without cooling and connects by cable to a separate electronics box. Exposure time is a very fast 110 µs.

• Temperature range: 86 °F to 3,362 °F (30 °C to 1,850 °C) across six models
• Spectral range: 2.3 µm
• Optical resolution: 12:1 (3MXL), 22:1 (3ML), 33:1 (3MH), 75:1 (3MH1, 3MH2, 3MH3)
• Smallest spot: 0.04 in (1 mm) with CF1 optics on the 3MH
• Exposure time: 110 µs (90%); response time 320 µs (90%)
• Sensing head: 0.55 in (14 mm) diameter × 1.10 in (28 mm) length, or 1.26 in (32 mm) with CF optics; up to 185 °F (85 °C) ambient without cooling
• Environmental rating: IP65 (NEMA-4). See the note in the Specifications tab
• Outputs: 0/4–20 mA, 0–5/10 V, thermocouple K, alarm; built-in USB
• Power supply: 8–36 V DC / 1.2 W

What it is used for

Some of the use cases for the Optris CTi 3M include:

• Metal temperature measurement: non-contact measurement of metal surfaces from 86 °F (30 °C) up to 3,362 °F (1,850 °C).
• Secondary metal processing: monitoring metal temperatures in downstream processing steps.
• Metal oxides: measuring oxidized metal surfaces, where the 2.3 µm range reduces errors from unknown emissivity.
• Ceramic materials: measuring ceramics across a wide temperature range.
• Small targets: measuring spots down to 0.04 in (1 mm) with CF1 close-focus optics.
• Tight installations: mounting the 0.55 in (14 mm) head in confined locations, with the electronics box sited remotely.

The model range

Six models split into two groups. The 3MXL, 3ML, and 3MH cover the lower bands at 12:1, 22:1, and 33:1, with flat measurement uncertainty of ± 2.7 °F (± 1.5 °C). The 3MH1, 3MH2, and 3MH3 all run 75:1 optics and switch to a proportional uncertainty of ± (0.3% of reading + 2.7 °F / 1.5 °C), which is the better basis at high temperatures.

Within the 75:1 group, the 3MH1 is noticeably noisier than its siblings: 200 mK NETD and ± 1.1 °F (± 0.6 K) repeatability, against 95 mK and ± 0.45 °F (± 0.25 K) on the 3MH2 and 70 mK on the 3MH3. If your process sits inside more than one model's band, the higher model is the quieter instrument.

Temperature ranges are scalable via the programming keys or software and app. Full optical, electrical, and environmental data is in the Specifications tab.

Key features

• 2.3 µm spectral range: reduces reading errors on materials with unknown emissivity.
• Low starting temperature: the 3MXL measures from 86 °F (30 °C).
• Miniature sensing head: 0.55 in (14 mm) diameter and 1.10 in (28 mm) long, or 1.26 in (32 mm) with CF optics, with an M12 × 1 thread.
• Head operates without cooling: up to 185 °F (85 °C) ambient.
• Fast measurement: 110 µs exposure time and 320 µs response time.
• Three optics options: standard focus, close focus (CF) at 4.3 in (110 mm), or close focus (CF1) at 1.2 in (30 mm) for spots down to 0.04 in (1 mm).
• Separate electronics box: with an LCD display showing 0.1 K resolution and programming keys.
• Flexible outputs: 0/4–20 mA, 0–5/10 V, and thermocouple K analog outputs, an alarm output, and built-in USB.
• Optional fieldbus interfaces: EtherNet/IP, Profinet, EtherCAT, Ethernet TCP/IP with Modbus TCP, Modbus RTU, RS485, RS232, or two optically isolated relay outputs.
• Three programmable I/O pins: external emissivity adjustment, ambient temperature compensation, uncommitted value, trigger (reset of hold functions), or alarm output.
• Signal processing: peak hold, valley hold, and averaging, plus extended hold functions with threshold and hysteresis.
• Software and app: configuration through Optris CompactPlus Connect software or the IRmobile app.

Why engineers pick it

Metal measurement from 86 °F. Six models span 86 °F to 3,362 °F (30 °C to 1,850 °C) with the same compact two-piece design, reaching lower than the 1M or 2M.

Less sensitivity to emissivity. The short 2.3 µm spectral range reduces reading errors on materials with unknown emissivity.

Small spots, close in. CF1 optics focus to 0.04 in (1 mm) at 1.2 in (30 mm), the only CTi sensor with a second close-focus option.

Flexible integration. Analog outputs, built-in USB, three programmable I/O pins, and optional industrial Ethernet, fieldbus, and relay interfaces.

Frequently asked questions

What distance-to-spot size ratio is correct for my application?

The size of the measuring object and the thermometer's optical resolution determine the maximum distance between the sensing head and the object. To prevent measuring errors, the object should fill the field of view of the optics. The spot should always be the same size as the object or smaller.

Which settings change if an external close-focus lens is used?

The optional CF lens allows measurement of small objects. When it is fitted on the CTi 3M, transmission must be set to 0.92. That matches the CTi 1M and CTi 2M but differs from the 8–14 µm sensors in the range (LT, LTfast, LThot, LTex), which use 0.78. The figure is an average characteristic value and may scatter between units, so determine it experimentally if your application requires it.

Can I shorten the cable between the sensing head and the electronics box?

On the CTi 3M the sensing head cable can be shortened by a maximum of 9.8 ft (3 m). This matches the CTi 1M and CTi 2M and differs from the 8–14 µm sensors, where shortening is discouraged and introduces an error of about 0.1 K per metre.

How do I exchange the sensing head?

Heads are connected and calibrated at the factory. Any exchange of sensing heads and electronics is possible within a given model group. Every head carries a specific calibration code printed on the head cable, and that code must be stored in the electronics box for correct temperature measurement and sensor functionality.

How can I improve the noise amplitude of the sensor?

Do not move the head cable during measurement. Use shielded cables only and ground the sensor shield. Avoid ground loops and related signal interference in industrial environments. It may be necessary to interrupt the ground connections inside the electronics box by switching the internal jumper to another position. Review the manual before doing so.

Can you connect two pyrometers to the same computer?

Yes. Using CompactPlus Connect or CompactConnect, depending on which pyrometers you have, you create separate instances of the software. Two pyrometers can be connected via the USB ports. Connection over RS485 is also possible, with the first pyrometer connected to the PC through the supplied RS485-to-USB adapter.

Accessories

• CF-lens (ACCTCFHT): close-focus lens for small spot measurement, M12 × 1.
• Mounting bracket, fixed (ACCTFB): fixed bracket for mounting the sensing head.
• Air purge collar with integrated CF-lens (ACCTAPLCFHT): keeps the lens clear in dusty or fume-laden process environments.

Configuring and scaling

Select the model, optics, and cable length on this page and use Request Quote to order. Cable lengths are 9.8 ft (3 m) standard, 26.2 ft (8 m), or 49.2 ft (15 m). Contact W5 for anything the selector doesn't cover, such as optional digital interfaces, relay outputs, and accessories.

Scope of supply

CTi 3M with a 9.8 ft (3 m) cable, mounting nut, and quick start guide.

Choosing between the CTi 3M, 2M, and 1M

All three are short-wavelength metal sensors on the same 0.55 in (14 mm) head, and they divide by temperature band. The CTi 3M measures at 2.3 µm from 86 °F (30 °C), by far the lowest start in the group, and reaches 3,362 °F (1,850 °C). The CTi 2M measures at 1.6 µm from 482 °F (250 °C) to 3,632 °F (2,000 °C). The CTi 1M measures at 1.0 µm from 662 °F (350 °C) to 3,992 °F (2,200 °C) and reaches highest. As a rule, the shorter the wavelength, the higher the temperature it suits. Note that the 3M head is limited to 185 °F (85 °C) ambient, against 257 °F (125 °C) for the 1M and 2M, so check the mounting location as well as the process temperature.

Get the CTi 3M specified and supplied

W5 Engineering supplies Optris infrared temperature measurement products. We match the model to your temperature range, target size, and working distance, then specify the optics, cable length, and any fieldbus interface you need. Contact us with your process temperature, measurement distance, and the ambient temperature at the mounting point, and we will return a configuration recommendation and quote.