Omron ES1-LWT Non-Contact Infrared Temperature Sensor

The Omron ES1-LWT is a compact, non-contact infrared (IR) temperature sensor designed for industrial process monitoring and control. It measures surface temperature of moving, hot, or electrically live objects without physical contact. With a measurement range of -20°C to 500°C and a linear 4-20 mA analog output, the ES1-LWT integrates directly with PLC analog input modules, providing real-time temperature data for closed-loop control, quality assurance, and predictive maintenance.

Measurement Specifications

• Temperature Range: -20°C to 500°C

• Spectral Response: 8–14 µm (long-wave infrared)

• Optical Resolution (D:S): 10:1 (standard) or 20:1 (with lens option)

• Accuracy: ±1°C or ±1% of reading (whichever greater) at 23°C ambient

• Repeatability: ±0.5°C

• Response Time (90%): 150 ms (adjustable digital filter up to 5 seconds)

• Emissivity Setting: 0.10 to 1.00 (adjustable via potentiometer or external voltage)

Optics and Field of View

The ES1-LWT features a fixed-focus optics with a distance-to-spot ratio of 10:1. This means at a distance of 100 mm from the target, the measured spot diameter is 10 mm. For smaller targets, the sensor can be positioned closer (minimum focus distance 50 mm). An optional 20:1 lens is available for measuring small parts at longer distances. The sensor head includes a visible laser sighting (class 2,<1 mW) for precise aiming, which can be turned off during normal operation.

Electrical Output and PLC Integration

The primary output is a 4-20 mA current loop (two-wire) proportional to temperature: 4 mA = -20°C, 20 mA = 500°C. This signal can be directly connected to any PLC analog input module (e.g., Omron CP1W-AD041, CJ1W-AD081) with a 250 Ω resistor to convert to 1-5V if needed. The sensor operates on a 24V DC power supply (10-30V DC range), drawing a maximum of 50 mA. An optional open-collector alarm output (NPN, 30V/50mA) can be set to trigger at a user-defined high or low temperature threshold, useful for direct PLC interrupt or indicator light.

Emissivity Adjustment

Emissivity (ε) of the target surface affects IR measurement accuracy. The ES1-LWT allows adjustment from 0.10 to 1.00 via an internal potentiometer or by applying an external 0-10V signal to the emissivity input (0V = ε 0.10, 10V = ε 1.00). For PLC-controlled emissivity, an analog output from the PLC can dynamically set ε for different materials in an automated process.

Mechanical Design and Environmental Ratings

The sensor head is housed in stainless steel (IP65 rated) with a M18×1 threaded body, length 95 mm, and a 2-meter shielded cable (4 wires: power+, power-, 4-20mA+, alarm output). Operating temperature for the electronics is 0°C to 70°C (without cooling); for the optics, 0°C to 150°C (with optional air purge/cooling jacket for higher ambient). Humidity: 10-95% non-condensing. Vibration resistance: 5 g at 10-55 Hz.

Applications in PLC-Controlled Processes

Common applications include: monitoring plastic extrusion temperature (non-contact avoids melt sticking), detecting overheating in conveyor bearings, measuring steel or glass surface temperature in annealing lines, controlling induction heating processes, and quality inspection of food products (baking, frying). The 4-20 mA signal allows a PLC to implement PID temperature control by adjusting heater power, fan speed, or conveyor speed.

Installation and Calibration

Mount the sensor with the target spot fully within the object's surface (avoid edges or background). For shiny metal surfaces (low emissivity), apply a high-emissivity coating (e.g., black paint, tape) or use the sensor at a shallow angle. Calibration is traceable to NIST; field verification can be done using a blackbody source or by comparing with a contact thermocouple at low temperatures (≤100°C). The sensor includes a built-in ambient temperature compensation circuit for accurate readings despite varying ambient conditions.

Standards and Compliance

The Omron ES1-LWT complies with CE (EMC Directive 2014/30/EU, EN 61326-1), RoHS, and is FDA compliant for the laser sighting (21 CFR 1040.10). It meets the measuring instrument standard EN 60947-5-2 for proximity sensors.

Ordering and Accessories

Standard model ES1-LWT includes sensor head, 2m cable, and mounting nuts. Optional accessories: air purge collar (ES1-LWTC) for dusty environments, water cooling jacket (ES1-LWTW) for ambient up to 200°C, and a 20:1 lens kit (ES1-LWTL20). A programming module (ES1-LWTP) allows advanced parameter adjustment via PC (emissivity curve, response time, alarm hysteresis).

Conclusion

The Omron ES1-LWT infrared temperature sensor provides reliable, non-contact temperature measurement from -20°C to 500°C with a standard 4-20 mA output for direct PLC integration. Its rugged design, adjustable emissivity, and laser aiming make it a versatile tool for industrial process monitoring and control.