Low-cost measurement of high temperatures in harsh environments

This new ratio pyrometer is suitable for OEMs that need to measure the temperature of metals, metal oxides, ceramic or semiconductor materials in harsh, high-temperature environments, including metal casting, welding, forming and sintering applications.

The thermoMETER CT ratio is a fibre-optic ratio pyrometer that measures temperatures from 700 up to 1800degC. By operating on the ratio principle, the sensor is insensitive to contaminants such as dust, smoke or steam that may partially obstruct the target. Even in cases where the infrared radiation beam is weakened to 95 per cent of its original intensity due to smoke or steam, the ratio pyrometer still provides high-integrity measurements.

Micro-Epsilon says that the compact dimensions and attractive price-performance ratio of the pyrometer sets a new standard. Chris Jones, Managing Director at Micro-Epsilon (UK), comments: "The CT ratio is another market-leading product from Micro-Epsilon. Technically, the product meets and exceeds the performance of all ratio pyrometers in the marketplace today, with the flexibility of multiple-output options and output signal flexibility, from simple analogue to digital and fieldbus interfaces. The low price level of just 1950 for the system is significantly below the price level of other ratio pyrometers and enables users to solve applications with this technology that previously were cost-prohibitive."

How it works

The fibre optics ratio pyrometer operates on the two-channel measurement principle: two integrated infrared detection channels with relatively close spacing but with different measuring wavelengths produce two independent electrical signals. These signals depend on the infrared radiation emitted from the target and signal components, which are influenced by the optical transmission path between the object and the pyrometer or from of the object if, for example, it moves or changes its size.

By taking the ratio of the two signals, the ratio pyrometer principle eliminates (or averages out) any signal parts that are similar in both channels. The measured temperature of the object therefore only depends on the signal ratio and the emissivity ratio (slope value).

When it comes to measuring the temperature of objects with unknown or changing emissivity, the ratio thermometer principle provides extremely accurate results, provided the emissivity ratio does not change over time or temperature.

Easy integration

The compact sensor head of the thermoMETER CT ratio pyrometer has a diameter of just 25mm and a length of 70mm, enabling it to be mounted into restricted spaces in production lines and machines. A fibre-optic cable connects the optical sensor head to the electronics. The optics and the cable can be used in ambient temperatures of up to 250degC without the need for additional cooling. By using a fibre-optic cable, the device is insensitive to electromagnetic interference (EMI) found in induction-based heat treatment processes and other electrically noisy environments.

Rapid temperature measurements with response times of 5ms can be achieved. An optical resolution of 80:1 with a selectable focus, in combination with built-in laser aiming, enables accurate measurements to be made from a spot size of 1.3mm diameter.

In order to adapt the sensor to different measurement tasks, the pyrometer offers a choice of a one- or two-channel (ratio pyrometer mode) device, which enables users to select the most appropriate one without having to specify different sensors.

Applications

Typical applications for the ratio pyrometer include: temperature control of inductive heating coils; temperature measurement of the pouring stream on casting machines; during the reheating of steel ingots and steel billets in forging processes; in general soldering and welding processes; and in process steps in semiconductor production and in photovoltaics.

The electronics simplify the programming of the sensor, display of temperature measurements and make for easy wiring of the analogue outputs (0/4-20mA and 0-5/10V). To facilitate network integration, Micro-Epsilon offers an optional integrated Profibus DP interface or other plug-in digital interfaces including USB, RS232, RS485 or Ethernet. Programmable signal processing provides flexibility for different production processes.

Micro-Epsilon also offers its user-friendly software that provides a graphical interface and display, and the logging of temperature readings from all output channels and signal characteristics over time. Users can also configure parameters and set up alarms such as 'dirty lens' alarms.

The standard focus of the lens is 60mm. However, an additional, variable-focus lens can be provided so that the focal point of the lens can be set anywhere between 65mm and 300mm.

Follow the link for more information on the thermoMETER CT ratio.