High Speed Fiber Optic Infrared Transmitter Is 'Spot-On' for Temperature Measurement
January 1, 2009
Omega Engineering, Stamford, CT, has introduced a high speed industrial fiber optic infrared transmitter and probe system, the OS4000, which offers many new and important measurement capabilities. These include an optical field of view or spot size as small as 0.025", which is less than half the size typically available, and a response time as fast as 1 msec, an order of magnitude faster than similar devices. Before we review this product, let's review this product category and take a look at some typical applications.
One of the most effective methods of making non-contact high temperature measurements in industrial applications is with a fiber optic infrared probe. These devices typically consist of a lens probe assembly which is aimed at the object to be measured, and a fiber optic interconnecting cable, which is connected to an electronics package, the transmitter, to make the temperature measurement and convert it into a useable output signal.
Although thermocouples are the most common temperature measurement devices in process control, they have their limitations. They must be in contact with the measured object, they have a slow response time, and they are subject to electrical and magnetic interference. Fiber optic infrared transmitters overcome these issues but are generally limited to reading temperatures above 100°C. This limitation is imposed by the fiber optic cable which cannot transmit infrared energy below a certain wavelength. This is dependent on the cross-section of the fiber optic strands and their optical properties. Following are some typical applications.
- Annealing Processes the critical surface temperature of the metal can be monitored directly while it is inside an oven, rather than indirectly by measuring the ambient oven temperature.
- Drill Bit Temperature Monitoring for high speed PC board drilling, wear can be determined by optically monitoring the drill bit temperature.
- Semiconductor Doping, Deposition or Sputtering since these processes are usually carried out in a vacuum or controlled gas atmosphere using induction heating, conventional temperature measurement devices cannot be used.
Because measurement conditions vary widely, several probe options are available; a fiber optic lens probe in which the lens determines the field of view, a fiber optic tip probe for general purpose applications, and a polymer bolt probe for immersion in polymer plastic flow, which is threaded so it can be inserted through a pipe or chamber wall. In addition to the common metal housing, there is a ceramic housing for high temperature conditions with a choice of glass or quartz tip assemblies. A built-in laser sighting aids in aligning the field of view to the exact measurement location. The transmitter contains the electronic package and converts the infrared signal into a useful format. It has a connector for the fiber optic probe at one end and one for power and output signals at the other end. The OS4000 offers a choice of analog outputs for connection to a display device, a data logger, or a process control system.
The OS4000 is a state of the art infrared measurement tool. The wide choice of analog output options, wide temperature range, probe assembly models, excellent software interface, and custom capability makes this product an excellent choice for infrared temperature measurement applications. When a spot size of 0.025" is needed or the sampling rate requirement is in the 1 msec range, then it is a no-brainer; choosing the OS4000 in these situations will be "spot-on."
© Copyright 2009 Omega Engineering Inc. All rights reserved. Reproduced with the Permission of Omega Engineering Inc., Stamford, CT 06907. www.omega.com