Power Spectra Laser Range Finder



Please be aware that this is an OEM product with a minimum order requirement of 100 pieces

Competitive Technology Comparison

The Power Spectra Laser Range Finder [PWSP LRF] is a laser based time-of-flight instrument.

Time-of-flight [TOF] measures the time it takes for a burst of light energy to get to the target and back.

Phase based [PB] units measure the relative phase of the modulation of the transmitted and received signals and then deduce the distance. The phase angle corresponds to time which corresponds to distance.

Ultra Sonic Devices [USD] transmit pressure waves and listen for the reflected energy.


LRF Technology Comparison

Category	PWSP LRF	PB LRF	USD
Update Rate	10Khz/1Khz	1Hz.	slow
Accuracy	1"/.4"	1 yd+	6" - 12"
Standard Temp and Pressure	not susceptible	not susceptible	susceptible
Range Gate	yes	no	no
Multipath distortion	distance to	weighted average	weighted average
	nearest largest	of distances to	of distances to
	target	reflected energy	reflected energy
Ability to seal	yes	yes	no
Susceptibility to ambient light	no	yes	no
Distance of measurement	1-100ft+	long range	1-20ft

The Update rate for the PowerSpectra TOF LRF is impressive at 1Khz. standard and optionally 10Khz. The individual samples are normally averaged to increase the resolution of the unit. A common setting is a moving average of 10. The update rate of the phase based LRF is closer to 1 per second -- not suitable for motion measurements. The Ultra Sonic devices have varying speeds of measurement, and suffer from the medium. In general ultra sonic update rates are slower than the LRF.

The accuracy of the PWSP LRF is better than 1 inch. The resolution can be increased with the number of samples averaged. With a typical set-up of 10 samples and 100 Hz updated [averaged data] the resolution is better than .375" and true motion can be measured. With 1 yard or more tolerance in accuracy the phase based LRF is better suited for long distance measurement where the error is a small fraction of the measurement. Ultra Sonic units are more accurate than the phase based unit at short distances, and less accurate than the PWSP LRF at all distances.

Ambient conditions are not a problem for the PWSP LRF with its industrial strength design and TOF measurement technique. Particulate matter, vapors, temperature, pressure can range greatly without affecting the accuracy of the measurements. The ultra sonic devices are greatly affected by all ambient conditions and depend on the speed of propagation of the sound energy which, is affected by the temperature and pressure. It is possible to compensate for the temperature and pressure, but expensive. The eye safe laser can operate at a much higher power output in the TOF design than the PB models. Because of the higher output power the PWSP LRF is nearly impervious to ambient lighting issues. The PB models can have problems with solar and other light sources because of the lower light energy that can be safely transmitted.

The PWSP LRF has a range gate feature which allows the operator to instruct the unit to ignore reflected energy that is too close. This is a useful feature whenever one is measuring a distance that is past something else: down a hall or through a window, for instance. The range gate can help make sure the measurement is to the target.

Multipath distortion is a problem with ultrasonic devices because of the multiple return paths and lack of control of the transmitted energy. The ultrasonic units broadcast energy in a much larger beam than the laser based units. Some of that energy will return to the unit from reflectors other than the target of interest. The Ultra Sonic unit will create a weighted average of the reflected energy received.

The PWSP LRF has a much smaller beam width and the range gate feature. The hardware is also designed to return one value -- the best reflector in the beam. With the PWSP design one will obtain a true reading and have the ability to train the beam on the desired target rather than getting the wrong distance based on multiple targets.

The phase based units also suffer from the multiple reflector situation. The beam width is much smaller than the ultrasonic unit, and the waveform is also distorted by the target. It is very difficult to select the one target and ignore the rest because of the distortion of the reflected signal. This is one of the major contributors to the 1 yd+ accuracy of the phase based units.

One of the practical advantages of the PWSP LRF when compared to the Ultra Sonic units is the ability to transmit through a sound barrier such as glass. The PWSP can be mounted to measure the distance of an object or liquid through a window. In an industrial setting this means that the measurement device can be separated from the item being measured. For example, in the food industry the PWSP LRF can be mounted above the tank and measure the height of the material in the tank while the ultra sonic device would have to be mounted within the tank. Obviously there are health, safety, maintenance and reliability of measurement advantages to being mounted on the outside. The accuracy of the measurement will also be improved, especially when the medium involves airborne interferors...steam, powder etc. The Ultra Sonic solution will provide false readings under these conditions and the PWSP LRF will make proper measurements.

Measurement distances are quite different for the three technologies. The accuracy of the phase based systems requires that the application be several hundred meters to reduce the error to an acceptable percentage. The ultrasonic and PWSP LRF measurement distances overlap. The PWSP LRF encompasses the ultrasonic distance and expands it to more than 100 ft.

For low cost applications at short distances with little or no movement and large tolerances available the ultrasonic unit will be less expensive than the PWSP LRF. If ambient conditions are not ideal, the length is greater than 20 feet, there is motion involved, or tolerances are small then the PWSP LRF is the solution. One can bandaid the ultrasonic technology to give better performance with temperature and pressure compensation and other specialized techniques to try to overcome the rest of the limitations. In the end the bandaided unit will be comparable in cost to the PWSP LRF and still not equal its performance.

For long range applications the phase based LRF may be the solution. The PWSP LRF beam width is set to approximately 1/3 degrees to allow easy target acquisition. For Distances up to 100 ft., motion tracking, dirty or sanitary environments, and high accuracy requirements the PWSP LRF is the clear choice.

Please Note: this is an OEM product with a minimum 100 piece order requirement


Preliminary Specifications

Laser Safety Class	Class I (fully eye safe) [FDA]
Beam Divergence	5.6 mrad [1/3Ÿ]
Wavelength	905 nm [near infrared]
Pulse Rate	1200 Hz.
Operating Range	.3-30 m (1-100 ft.), 20% surface - non-cooperative target(1)
	1-100m (1-330 ft.), 90% surface - White Wall(1)
	1-300m (1-1000 ft.), Plastic Reflector
Accuracy over Temperature Range	<1 cm (.4 in.) typical
	2.5 cm (1 in.) absolute (2)
Resolution over Temperature Range	1mm (0.04 in.) (2)
Accuracy, single shot	+/- 1.5 in.
Repeatability	5 mm [.2 in]
Measurement Rate	5-1200 Hz
Accuracy, integrated	+/- 1.5 in. divided by the sqr root of samples[1-256]
Computer Interface	Bi-directional RS-232 @ 19.2 kBaud
Analog Output	4-20 mA
Power Requirement	10-28 Vdc, 7 W max.
Rating	UL, CSA, EC
Storage Temperature	-20Ÿ to +60Ÿ C
Operating Temperature	0Ÿ to + 35Ÿ C currently (-10Ÿ to +50Ÿ C soon)
Humidity	0-95%, non-condensing
Enclosure Rating	NEMA 6
Size (approximate)	105mm (4.125 in.) H x 152mm (6.0 in.) W
	x 108mm (4.25 in.) D
Weight	1.5 kg (3.3 lbs.)
Mounting	bottom and/or sides tri-pod threaded std. mt.
Standard Accessories
1.	Built in sighting scope
2.	AC/DC power adapter with connector
3.	RS-232 serial cable (6')
4.	User Manual
5.	User Software (Windows 95)
Optional Accessories
1.	Power Cable with connector
2.	Mountable 3" plastic reflectors
3.	RS-485 serial interface upgrade
4.	57.6K baud upgrade
5.	Increased pulse rate to 9600 Hz(3)
DATA INTERFACE
J1 - RS-232 Connector - 9 Pin, Serial
	J2 - Power (+6 to +30 Vdc) Connector
J1-1 Not Connected
J1-2 Data Out (RS-232 XMT)	J2-1 Power Input -- Outer
J1-3 Data In (RS-232 RCV)	J2-2 Power Ground -- Inner
J1-4 Not Connected
J1-5 RS-232 CTS	J3 - Analog Signal(4-20 mA) Connector
J1-6 Not Connected
J1-7 RS-232 RTS	J3-1 Analog Ground -- Outer
J1-8 Not Connected	J3-2 Analog Signal -- Inner
J1-9 Signal Ground

(1) Refers to percent reflectivity to diffuse surface.
(2) Based on averaging 64 shots/measurement across temperature range (0C-35C)
(3) Increased laser pulse rate may exceed FDA Class 1 limits.
(4) Optics must be kept free of moisture, condensation and dust accumulation.
(5) Performance may vary over range depending on size and reflectivity of target.

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