Description:The T-GAGE sensor is a passive, non-contacting, temperature-based device from Banner Engineering, combining the ease-of-use of a photoelectric with the brain power of a more sophisticated sensor. It activates an output when it detects objects that are either hotter or colder than the ambient condition. The output can be used to verify and inspect control processes.
Q: When would I use a temperature sensor?
A: Use a temperature sensor to measure objects that are inaccessible, extremely hot or moving too fast. If you have an application in which you must monitor extreme temperatures that might damage other types of sensors, you might want to consider a T-GAGE. Some applications include: hot part detection, ejection verification of injection-molded parts, flame process verification, hot glue detection, cold part detection and roller monitoring.
Q: How does a temperature sensor work? A: The T-GAGE looks and operates as easily as an Expert photoelectric sensor. The T-GAGE is different in that it detects the infrared light energy emitted by objects instead of its own emitted light. That’s why it’s considered a passive device. The sensor uses a thermopile as a receiver element to detect the emitted infrared energy within its field of view. This information is measured and analyzed by an ASIC, and depending on the thermal contrast, an output is given.
Q: How far will it sense? What is its range?
A: The practical range of the T-GAGE is limited only by the sensing environment, item size and sensor’s field of view (FOV). Ideally, the range is the distance where the FOV is completely filled. Remember, as you move away from the item to be sensed, the surrounding area’s ambient temperature begins to reduce the thermal contrast.
Q: Why is the sensor’s field of view (FOV) so important?
A: If the target object is smaller than the sensor’s FOV, the actual temperature sensed will be an average of that object and everything else in the FOV. This can affect the thermal contrast. By filling the field of view with as much of the target object as much as possible, you increase the thermal contrast leading to a more reliable output.
Q: What do you mean by “thermal contrast?”
A: It is the temperature difference between ambient temperature and the item to be sensed. High thermal contrast increases switching accuracy.
Q: How do I know if my target fills the sensor’s field of view (FOV)?
A: The FOV is defined by target and the selection of the lensed thermopile. Choose between three D:S ratios of 6:1, 8:1 or 14:1. The goal is to fill as much of the FOV as possible with the target. Although the thermopile is lensed, it still can be influenced by intense incidental signals beyond the focal range.
Q: What is the D:S ratio?
A: D:S ratio refers to the sensor’s distance-to-spot size ratio which is inversely related to the viewing angle. A sensor with a small viewing angle will have a large D:S ratio. For a sensor with an 8:1 ratio, the sensor’s spot size is a 1" diameter circle at a distance of 8". As you go out further from the sensor face, the spot size will be larger.
Mouse over the D:S ratio below and see how the viewing angle changes.
Q: How do I know if I'm aiming at the target object?
A: The sensor is barrel-shaped so the viewing will be off the end. Mechanical and optical alignment are accurate within +/- 3 degrees. In more complex sensing environments, we offer a laser alignment accessory.
Q: What if my target object is in a hot oven? How will the sensor detect it?
A: The T-GAGE can switch at temperatures above the 300 °C range, however the T-GAGE is most efficient when there is high thermal contrast, such as when switching between ambient temperature and hotter than ambient. Here’s an analogy: It’s more difficult to hear someone shouting in a loud factory environment than it is to hear someone shouting in a quiet office.
Q: How quickly does the temperature sensor reach a final temperature reading?
A: A sample takes 25 milliseconds; the device requires one on and off cycle, so the actual response must be considered 25 milliseconds on and 25 milliseconds off.
Q: How do I make sure the temperature sensor isn't measuring background objects?
A: Be sure that the target fills the entire field of view (FOV), and ALWAYS try to eliminate potential hot objects that might be picked up by the FOV.
Q: I have a very harsh environment. Can this sensor handle it?
A: The T-GAGE is housed in a 18mm rugged stainless steel barrel that can withstand environments such as those found in food processing, metal manufacturing, construction and transportation industries.
Q: What's the temperature range of this sensor?
A: Our present sensor can sense temperatures from 0° to 300°C.
Q: What's the hottest temperature it can sense?
A: It can sense temperatures hotter than 300°C but it’s possible to saturate the circuit. Higher temperatures can still be taught as an output provided there is significant thermal contrast between the taught temperature and ambient.
Q: What temperature difference does it need to switch?
A: The T-GAGE can switch with a change of 3° C or 6° F.
Q: Does this sensor provide an absolute temperature reading?
A: No, the T-GAGE provides a relative temperature reading. Absolute temperature is an exact reading with known calibrated sources as base reference, while relative temperature readings are only approximate. Absolute temperature requires enormous calibration certainty and is cost prohibitive for most simple automation processes; relative or observed temperature indication devices can be produced in a far more cost effective manner.
Q: How do I set the relative temperature?
A: This device is calibrated at the factory and doesn’t need to be adjusted in the field. Keep in mind, this sensor is basically an on/off switch.
Q: Is there a way to estimate an object's temperature by its color?
A: The US Navy published guidelines for steel, and while not “absolute” they have proven very useful over the decades. For example, “red hot” steel is ~1077° F (581° C).
Q: What is emissivity?
A: All materials and surfaces emit and absorb energy. Emissivity is a measurement of the thermal signature and characteristics of different materials and surfaces. Anything in nature with a temperature above absolute zero emits energy. Emissivity measurement is represented as a ratio of energy emitted by an object at a given temperature to energy emitted by a blackbody at the same temperature. A blackbody is a perfect radiator with an emissivity of 1. Typical objects have an emissivity of .5 to .98. On the opposite end of the spectrum, a mirror has an emissivity of 0. Be aware that shiny surfaces may provide erroneous signals to the thermopile receiver. Matte surfaces tend to be fairly accurate.
Q: Is there an emissivity rating system for surfaces?
A: Emissivity is a ratio between an absolute radiator of energy and the object in question. We measure the blackbody with no reflectance as having an emissivity of 1. A highly reflective surface, such as a mirror, has an emissivity of 0. Most objects in between have an emissivity of .5 to .98.
Q: How do I figure out the emissivity of my surface?
A: Emissivity is not easy to measure because it depends on many different properties: temperature, wavelength, angle, oxidation and surface texture. While there are rather involved ways to measure emissivity, the general rule is shiny, unpainted metals have low emissivity while non-glossy, matte surfaces have high emissivity. Consult a Banner Application Engineer about how to increase your emissivity reading.
Q: At what minimum distance can the T-Gage detect an object?
A: Because the T-GAGE is a passive infrared receiver, there is no dead-zone or blind spot in front of the lens.
You can mount the T-GAGE all the way up to the surface of the target, as long as it doesn’t physically impact the sensor. Always observe the top temperature specification of the sensor. If the sensor is too close to an extremely hot target, the sensor's circuit may overheat.
A: The T-GAGE looks and operates as easily as an Expert 