Source: http://www.nhtsa.gov/people/injury/speedmgmt/speed_lidar_module/pages/5TestProcedures.html
Timestamp: 2013-12-08 12:49:16
Document Index: 254249995

Matched Legal Cases: ['§4', '§2', '§2', '§2', '§2', '§5', '§2', '§5', '§5']

DOT HS 809 812
Section 5 - Test Procedures
5.1 (Reserved) 5.2 (Reserved)
5.3 Labeling and Operation Tests
With the lidar unit in hand, the test engineer shall review the instructions and the markings on the controls to verify that the controls operate as explained in the manual and consistently with their markings. The simulator or normal traffic may be used for input data. It is permitted for controls to have secondary functions beyond those marked; in these cases, there is a particular obligation for the manual to be written in plain English and to describe the use of the controls accurately.
While it is impossible for this test to be exhaustive, the test engineer shall look for:
(a) controls that are unmarked, or marked in a misleading way;
(b) modes of operation that are not documented;
(c) misleading labels appearing in an alphanumeric display; and (d) lack of clarity in the manual, including possible typographical errors.
No misleading wording is permitted on the control panel and display, or in the manual. If an undocumented mode does turn up, such as an engineering test mode for instance, the resulting display shall be clearly different from the display in normal speed-measurement mode.
5.4 Range Accuracy
This test applies only to the accuracy of measurements of the distance to stationary targets. Target ranging shall be checked on the two measured baselines. The reference plane on the lidar unit is the front surface (the surface with the lenses) unless the manufacturer has clearly defined a different reference (see fig. 2). Set the lidar unit at the predetermined height (§4.3) and aim it at the correct target area. If the surveyed distance is not an integer number of meters or feet, corresponding to the system of units of the lidar device, make an auxiliary mark a fraction of a meter (or foot) forward of the fiduciary mark so that the range becomes an integer number of units. Repeatedly record the target range or error indication until five range measurements are recorded. All five readings must be correct to a tolerance of ±0.3 m (±1 ft). Perform this test and calculate the arithmetic mean of the readings for each of the pre-surveyed baselines. 5.5 Long-range Test
Elevate the long-range target (see fig. 6) so that its center, as seen from the lidar UUT, is at least 2 m above the ground or other obstacle. The background should be sky. Determine the greatest range at which the lidar unit can measure the distance to the target. Pay attention to the beamwidth of the UUT and the target's clearance from the ground; be sure that the UUT is ranging to the target and not something else. If a range exceeding 300 m (1000 ft) has been measured and conditions do not permit the UUT to be backed farther away, the test may be stopped. Record detailed observations as the lidar operator moves back from the target, including all distances at which the UUT obtained range measurements and the reason for stopping the test.
5.6 Beam Characteristics Test
Set up the apparatus as illustrated in Figure 7. Note that this figure is not drawn to scale but is dimensioned to verify beam alignment, range accuracy, and beamwidth. Mount the lidar unit under test (UUT) upright on a tripod with the laser beam parallel to the ground (floor) and at the same elevation as the center points of the targets. The tripod mount shall permit the UUT to be rotated so the centerline of the laser beam can be aimed at the center point of each target. To facilitate aligning the laser beam with the target, a small flashlight may be held just above the target. The flashlight must be removed before the test readings are taken. A 60-inch carpenter’s level may be used to help align the front of the UUT with the reference mark.
5.6.1 Beam Alignment. 5.6.1.1 Horizontal. Slowly sweep the beam horizontally across target TC and observe that the range of TC is displayed only when the target is in the reticule of the sight, indicating lateral alignment.
5.6.1.2 Vertical. Rotate the UUT on its side on the tripod, so that it is at a right angle to its normal position. Repeat the process to verify vertical alignment.
5.6.2 Range. Aim and record the distances to each of the three targets: TL, TC and TR. Repeat until ten range measurements have been recorded for each target. Verify that the UUT is capable of measuring and displaying the correct range to each target.
5.6.3 Target Discrimination.
5.6.3.1 Horizontal. Carefully sight the UUT at the space between TL and TC to demonstrate that the lidar beam is slender enough to pass between the targets without causing a reflection and range reading from either target. Repeat for targets TR and TC.
5.6.3.2 Vertical. Turn the UUT on its side on the tripod mount and repeat the procedure to verify that the beamwidth requirement is also satisfied in the vertical plane of the UUT.
5.7 Environmental Tests
5.7.1 Operational Temperature Test. Choose three speeds within the capability of the UUT and store them in a file for use by the simulator software as a "Standard Speed Series." (The speeds should be integer values in the UUT native system of units.) Place the UUT, with the power off, in the environmental chamber and adjust the chamber to the required low temperature, TdLow ±2 ºC (±3.6 ºF). Allow the UUT to reach thermal equilibrium and maintain it at this temperature for 30 min. Prepare the simulator hardware and software so it is ready to run a test. Use protective gloves and remove the UUT from the environmental chamber. Connect the UUT to the standard supply voltage, turn it on, and optically couple it to the simulator. Measure the PRR and then test the UUT at the three simulated speeds. Work quickly, as frost may be forming on the external lens surface. Perform the high temperature test during the same day to dry out the unit.
A simulator test should remain valid despite a thin layer of frost. If the UUT fails to read the simulated speed accurately, repeat the test. The UUT shall meet the requirements of §2.7 within 15 min of operation. Any external frost in itself is not an intended feature of this test, and if it is possible to reduce ambient humidity, this may be done.
Repeat the test just described at the required high temperature, TdHigh ±2 ºC (±3.6 ºF). In the high-temperature case, energize the UUT when it is removed from the chamber, but wait 2 min before performing any measurements, including the test of PRR.
If the UUT is a lidar system, then repeat the test just described at the required low temperature, TsLow±2 ºC (±3.6 ºF). If the UUT is a lidar system then repeat the test just described at the required high temperature, TsHigh±2 ºC (±3.6 ºF). 5.7.2 Operational Humidity Test. Place the UUT, with the power off, in a humidity chamber. Adjust the relative humidity to a minimum of 90 % at 37 ºC (99 ºF) and maintain the UUT at these conditions for at least 8 h. Remove the UUT from the chamber and bring it quickly to the simulator. If the UUT is a lidar system, wait for the UUT to cool to TsHigh. Connect the UUT to the standard supply voltage, then wait 2 min before performing any measurements. The UUT shall meet the requirements of §2.7 within 15 min of operation.
5.8 Low Supply Voltage Indicator Test
A simple connection box, as shown in figure 8, will permit meters to be connected for measurement of voltage and current. Comparison with figure 3 will show that this can be the same box used to inject the pulse and sawtooth signals.
Connect the lidar UUT to the adjustable supply voltage and properly couple its optics to the target speed simulator. Switch the UUT on and let it warm up for 2 min at its standard supply voltage. Set the system to consume maximum power. Set the target speed simulator to simulate a vehicle moving at 110 km/h (70.0 mph). Measure the simulated speed with the lidar unit. Decrease the lidar unit’s supply voltage by 0.2 V and again measure the simulated speed. Continue to decrease the supply voltage and measure simulated speed until the low voltage alert is activated. Record the supply voltage level. Send each reading to the computer file, annotated by the voltage at which it occurs. No erroneous speed reading should occur. Increase the supply voltage until the low voltage indicator is deactivated, and again measure the simulated speed to verify that the UUT reads 110 km/h (70.0 mph).
Also, for a battery powered lidar device designed to accept a 12 V automotive adapter, verify that when using this adapter the device works properly down to its low voltage alert level. The lowvoltage alert levels are specified in §2.8.
5.9 Supply Voltage Tolerance Tests
Use the setup as in the previous section with a meter to monitor the supply voltage to the lidar UUT. Determine the working voltage range according to §2.9. 5.9.1 Pulse Repetition Rate. For units capable of a fixed PRR, set the simulator to measure PRR. Step through voltages as in §5.8, reaching the high and low limits according to §2.9 while noting the voltage and PRR. Be sure to record all digits of the PRR. The PRR shall not vary by more than 0.1 % from its value at standard supply voltage.
5.9.2 Range and Speed. In this part, the simulator software can be used to record the data. Prepare a table of distance-speed combinations according to the approach in §5.11. Set the simulator for normal speed simulation, including the description of the UUT. Next step through the voltage range as in §5.9.1, setting a different distance and speed at each voltage step. The UUT shall not display any erroneous speed readings. A blank display is not considered an erroneous reading. If a blank occurs, the test must be repeated, and an accurate non-blank speed must be obtained at each step.