SEN FAQ:
Yes, lasers for materials measurement have been an established technology in industrial applications for over a decade. While relatively new compared with ultrasonic and radar, lasers have continued to expand their application base. LTI has been selling into industrial applications for over 10 years. We are installed in steel mills, bulk material handling, railroads, vehicle guidance and positioning applications, and many more.
No one sensor technology provides the best solution in all cases. TOF lasers offer a non-contact measurement device that can read off almost any surface, is highly accurate, can read over long ranges, and is generally easy to set up and use. Laser technology is relatively new to industrial sensors. In the past, laser sensors have been perceived as too expensive or too specialized. But LTI has brought the price point for laser sensors down to competitive levels, and their use has become much more widespread. Below is a table that summarizes the main advantages of TOF Lasers, as compared with other technologies.
Pulsed, 905 nanometers (nm), time-of-flight (TOF) lasers. 905 nm is the wavelength of the infra-red light of the laser (this wavelength lies just outside the visible light spectrum that ranges from 400 nm to 730 nm). TOF signifies the time of flight of the pulse is measured to determine distance
LTI lasers send out pulses of light at a rapid rate (the speed of light), which reflect off target surfaces, and travel back to the laser. The timing of the return pulse is precisely measured which enables the distance to be calculated.
The ULS ranges from <1 Hz to 2000 Hz; the S Series ranges from <1 Hz to 14 Hz
Reflective, or cooperative, targets reflect the laser pulse much better than a non-reflective, or non-cooperative target. Therefore, you can measure objects that have reflective targets at a longer distance than those with a non-reflective target. A non-reflective, or non-cooperative target is a target that does have any special reflective characteristics. Most natural object are non-reflective. If the target is non-reflective, the laser pulses don’t reflect off it as well, so you get a weaker signal back. Therefore, it cannot measure to as long a distance. Even among non-reflective targets, some colors reflect better than others. For example, the color
white reflects more than a darker color. Even a target that is gray instead of white has significantly less reflectivity than white. In most cases, however, this is not a critical factor, only in those with longer ranges or where the laser has trouble picking up a reflection at all.
Yes, all LTI sensors are rated Class 1 for eye safety. But, it is always a good practice not to stare directly into the transmit aperture of any light transmitting device.
The ULS has slightly better accuracy (+/- 2 cm), better ability to look through dusty and hazy environments, better ability to work in adverse conditions, and comes in a more rugged housing (aluminum versus glass-filled polycarbonate).
The S200 Series has up to +/- 4 cm accuracy, is housed in a glass-filled polycarbonate packaging and has a smaller footprint. It has an explosion-proof accessory (Ruggedized Enclosure) which allows it to be rated to meet ATEX and other explosion-proof standards. It is ideal for applications such as level detection or short-range detection of simple targets.
Both the S210 and the S230 come with an alignment laser to facilitate laser alignment.
Pulse Repetition Frequency (PRF) is how fast the sensor is sending out laser pulses. This is important because a faster PRF can take more measurements or detect something at higher speeds, or use more pulses to get a better average. PRFs in the ULS can be set from 1 to 4,500 depending on the mode. PRFs in the S200 Series are set at 2,800 pulses per second.
No, it is fully calibrated before it leaves the factory and will work to any distance within its specified range.
By their very nature, lasers produce a very narrow beam that can be precisely aimed at a target. This is just one of the features that sets laser sensors apart from other sensor technologies, such as ultrasonic or radar.
Beam diameter over distance can be calculated as follows:
Example:
The S200 series is lighter in weight, smaller in size, has a smaller footprint, with nearly the same accuracy, some of the same target selection capabilities, and costs significantly less.
For strong targets, use First or Strongest target modes. For targets in dusty or hazy environments, Last Target Mode is generally recommended.
The S200 has RS232 as well as a 0-5 VDC output trigger that makes it versatile depending on what output you need. The S210 has RS-232, SDI-12, and the trigger. The S230 has RS-232 and 4-20 mA.
The S200 series has three standard target modes: first, last and strongest.
The S200 series also supports several advanced target modes, which can used under very specific circumstances.
If the water is very clear and still, the laser will likely read through the water’s surface, to some point below the surface level. If the depth of the water is very low (say, six inches), the laser may read to the bottom of the tank or vessel containing the water. In either case, if the intent is to measure the water surface under these conditions, the laser sensor will not provide an accurate, consistent measurement.
They can if the water has some color or contour to it, such as rapids. Lasers have more of a problem if the water is clear.
Typically, no. Unless the foam is very low-density and laser light will get through it, the laser can only measure to the top of the foam. However, the customer may be able to use a standpipe, which is separate from the main liquid but still has the same liquid level in it. It may not have the foam, so readings could be made in the standpipe and have accurate measurements. They also may be able to create a small “wash-down” area at the side of the tank which will flatten out the foam.
The presence of steam is a challenging condition. Like most scenarios, it depends on the density & composition of the steam and the nature of the surface to be measured: composition, clear or opaque; still or turbid, etc. A good general rule of thumb is that if you can see through it, the laser will be able to as well. If not, neither can the laser. There are some exceptions – some material reflects infrared rays more than visible light, so it might look relatively clear but the laser still will not penetrate it.
Borosilicate glass typically works well. Also, there is no degradation using plain glass or even plastic. When measuring through glass, it is recommended the face plate of the sensor be 3mm or closer to the glass. Light passing through the glass will create reflections and larger gap could result in measurement error. If there are any questions or uncertainties, it would be best if the customer can get a transmission curve for the glass they are considering and send it to us for review.
The S200 sensor family has the following accessories available:
A Class 1M laser is safe for all conditions of use except when passed through magnifying optics such as binoculars and telescopes.
The ULS is a rugged laser sensor that fits into many applications and is easy to set up and operate. It has several different targeting or measurement modes which allow it to be optimized for different industrial applications. It can work in dusty and dirty applications and measure up to +/- 2 cm accuracy. It can also measure to about a mile to a reflective target and 1/3 of a mile to a non-reflective target.
The ULS comes with the following accessories:
