The Optris CTi LTex is a two-piece infrared temperature measuring system for applications in hazardous areas. It pairs a passive IR receiver, the sensing head, with active evaluation electronics. The sensing head can be installed as a passive element inside the hazardous area, with energy to the head limited by two R. STAHL zener barriers approved for zone 1. The electronics and both barriers mount together in an aluminum housing for installation in zone 2, division 2, or the safe area. Sensing heads are exchangeable, each carrying an individual calibration code as its head ID.
Measuring principle: passive IR sensing head with active evaluation electronics
Hazardous-area concept: intrinsically safe by energy limitation with two R. STAHL zener barriers
Sensing head classification: simple electrical device according to EN 60079-0 / EN 60079-11, to be verified by the operator
Barrier types: 9002/22-032-300-111 and 9002/11-137-029-001 (R. STAHL AG)
Barrier approvals: Europe PTB 01 ATEX 2053X (zone 1) and PTB 01 ATEX 2054X (zone 2); IECEx PTB 08.0057X; USA UL E81680V1S3; Canada CSA 1284580 (LR 43394)
Barrier installation location: zone 2, division 2, or safe area
Optics: 2:1, 15:1, or 22:1
Sensor cable: 9.8 ft (3 m), 26.2 ft (8 m), or 49.2 ft (15 m), shielded type FEP TD 833 CF
Housing: CA-215 aluminum with mounting rail for both zener barriers and the CTi LTex electronics
Barrier environmental rating: IP67, –4 °F to 140 °F (–20 °C to 60 °C). See the note in the Specifications tab
At a glance
Passive sensing head installs as a simple electrical device in hazardous areas
Intrinsically safe by energy limitation with two zone 1 zener barriers
ATEX, IECEx, UL, and CSA barrier approvals for global installations
Supplied as a system in one aluminum housing with 2:1, 15:1, or 22:1 optics
Concept
Passive head, safe electronics
Only the passive IR receiver enters the hazardous area. The active evaluation electronics stay in zone 2, division 2, or the safe area.
Protection
Two zener barriers
Energy to the sensing head is limited by two R. STAHL barriers with zone 1 approval, one on the sensor signal and one on the head temperature sensor.
Approvals
ATEX, IECEx, UL, CSA
Barrier approvals cover European zones, IECEx, and North American class, division, and group classifications.
What it is used for
Some of the use cases for the Optris CTi LTex include:
Temperature measurement in hazardous areas: installing the passive sensing head inside a hazardous zone.
Zone 1 installations: using the approved zener barriers for energy limitation to the sensing head.
North American classified locations: applications covered by the UL and CSA approvals for the barriers.
Retrofitting existing installations: swapping sensing heads, each identified by its individual calibration code as head ID.
Documented intrinsic safety verification: using the manufacturer's declaration of cable and sensing head inductance and capacitance.
Key features
Passive sensing head: the IR receiver can be installed as a passive element in hazardous areas.
Energy limitation by zener barriers: two R. STAHL barriers, type 9002/22-032-300-111 and 9002/11-137-029-001, with zone 1 approval.
Complete system housing: a CA-215 aluminum housing with mounting rail for both zener barriers and the CTi LTex electronics.
Separate barrier per circuit: the sensor signal and the head temperature sensor each pass through their own barrier.
Exchangeable sensing heads: each head carries an individual calibration code as its head ID.
Three optical resolutions: 2:1, 15:1, or 22:1, with three selectable cable lengths.
Documented cable and head data: the manufacturer's declaration lists cable inductance and capacitance and the sensing head capacitance for intrinsic safety verification.
Why engineers pick it
Measure inside the hazardous zone. Only the passive sensing head enters the hazardous area. The active electronics stay in zone 2, division 2, or the safe area.
Approved barrier concept. European, IECEx, UL, and CSA approvals for the zener barriers used.
Supplied as a system. Sensor, both zener barriers, and electronics come together in one aluminum housing, so the protection concept arrives assembled rather than specified separately.
Documented for verification. The manufacturer's declaration under EN 60079-11 item 5.7 gives the cable and sensing head values needed for the operator's intrinsic safety assessment.
Important note
The functionality and correct reading of the CTi LTex sensor can only be guaranteed if the recommended barriers are used. Substituting a different barrier type will affect both the measurement and the protection concept.
Classification of the sensing head as a simple electrical device must be verified by the operator. Optris provides the manufacturer's declaration under EN 60079-11 item 5.7, but responsibility for the installation assessment rests with the operator.
Frequently asked questions
Can I use the CTi LTex as a 2-wire sensor?
No. Do not connect a supply voltage to the analog outputs, as this will destroy the output. The CTi LTex is not a 2-wire sensor. If you need a two-wire device, review the Optris CSmicro series instead.
Can I shorten the cable between the sensing head and the electronics box?
It is not recommended, because the cable's impedance forms part of the sensor calibration. On all CTi LTex models the sensing head cable can be shortened if necessary, but doing so introduces an additional measuring error of about 0.1 K per metre removed. On this product the cable also carries documented inductance and capacitance values used in the intrinsic safety assessment, so any change should be reviewed against that assessment.
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, transmission must be set to 0.78. That figure is an average characteristic value and may scatter between units, so determine it experimentally if your application requires it. Confirm with W5 that a CF lens is available and permitted for your hazardous-area installation before specifying one.
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, and confirm any change against your installation's intrinsic safety assessment.
Configuring and scaling
Select the optics and cable length on this page and use Request Quote to order. Optics are 2:1, 15:1, or 22:1, and cable lengths are 9.8 ft (3 m), 26.2 ft (8 m), or 49.2 ft (15 m). Contact W5 for anything the selector doesn't cover, including approval documentation for your installation and the measurement specifications for your chosen optic.
Scope of supply
CTi LTex sensor with the selected optics and cable length; aluminum housing with mounting appliance for two zener barriers and the CT electronics; two zener barriers, type 9002/22-032-300-111 and 9002/11-137-029-001; mounting nut; quick start guide.
Get the CTi LTex specified and supplied
W5 Engineering supplies Optris infrared temperature measurement products. Hazardous-area installations need the zone or division classification, gas or dust group, and temperature class settled before the sensor is specified. Contact us with your area classification, process temperature, target size, and working distance, and we will return a configuration recommendation, the approval documentation you need, and a quote.
