Features:

• Measuring range: 0.2 m to 200 m
• Typical accuracy: ±1.5 mm (DLS-A15), ±3.0 mm (DLS-A30)
• Precision: 0.1 mm
• Typical measuring time is 0.3 seconds, longer for some target surfaces
• Up to 10 units may share a single RS-422 line
• Programmable analog output
• Digital output for error signalling
• Flexible power requirements: 9-30 VDC
• Solid aluminum housing
• Dimensions (Height x Width x Length): 53 x 80 x 153 mm (2.1 x 3.1 x 6.0)
• Can be mounted with three M4 screws
• Temperature range −10C to +50C (−10C to +45C in continuous operation)
• Expanded-temperature models available for −40C to +50C (−40C to +45C in continuous operation)

Allen-Bradley 45BPD sensor

ranges from 30mm to several metres

ideal non-contact solution for error proofing, inspection, positioning and measurement applications

Features:

· no user adjustment and its 0 to 10V DC analogue output is scaled linearly over the entire sensing range

· two selectable sensing ranges of 30 to 100mm and 80 to 300mm.

· discrete PNP output and also a 4-20mA analogue output (automatically scaled between the set-points)

· visible red class 2 laser (simplifies alignment in small part detection and measurement applications)

· distance measurements from 0.2m to 6m.

THE DME 5000

new laser distance measurement device

multi-functional switching outputs for standby, preset and other system functions;

device display with all the information available at a glance, and a particularly user-friendly mounting and alignment concept, compact device.

Features:

· temperature range +55°C to -40°C; also suitable for use in deep-freeze storage plants.

· used for determining the position of storage and retrieval devices in automated warehouse technology.

· suitable for process speeds of up to 10m/s

· accuracy of ±2mm with a reproducibility of 0.5mm

· during subsequent operation, the illuminated display shows all the important status and diagnostic functions at a glance.

· two multi-functional switching outputs, e.g. for pre-defined distance values, temperature warnings or an advance pre-fault warning.

· has CSA and UL approvals.

Make presentation on the topic: “Distance measurement devices”.

Read and translate text B.

TEXT B

Time-of-Flight, Triangulation, or Field Based approaches

There are many different classes and instances of noncontact ranging devices, but with very few exceptions they are based on one of the following three basic principles:

1. Energy propagates at a known, finite, speed (e.g., the speed of light, the speed of sound in air)

2. Energy propagates in straight lines through a homogeneous medium

3. Energy fields change in a continuous, monotonically decreasing, and predictable manner with distance from their source

The techniques associated with these basic phenomena are referred to as time-of-flight, triangulation, and field based, respectively.

Time-of-Flight

Time-of-flight (TOF) systems may be of the “round-trip” (i.e., echo, reflection) type or the “one-way” (i.e., cooperative target, active target) type. Round-trip systems effectively measure the time taken for an emitted energy pattern to travel from a reference source to a partially reflective target and back again. Depending on whether radio frequencies, light frequencies, or sound energy is used, these devices go by names such as radar, lidar, and sonar. One-way systems transmit a signal at the reference end and receive it at the target end or vice versa. Some form of synchronizing reference must be available to both ends in order to establish the time of flight.

A characteristic of many TOF systems is that their range resolution capability is based solely on the shortest time interval they can resolve, and not the absolute range being measured. That is, whether an object is near or far, the error on the measurement is basically constant.

Triangulation

Triangulation techniques were known and practiced by the Ancients. Triangulation is based on the idea that if one knows the length of one side of a triangle and two of its angles, the length of the other sides can be calculated. The known side is the “baseline.” Lines of detection extend from either end of the baseline to the target point. A surveyor uses a precision pointing instrument to sight a target from two positions separated by a known baseline. Reference notes that the distance to a nearby star may be calculated by observing it through a pointing instrument at 6-month intervals and using the diameter of Earth’s solar orbit as the baseline. Stereo ranging, which compares the disparity (parallax) between common features within images from two cameras, is another form of passive triangulation. It is of interest to note that human vision estimates distance using a variety of cues, but two of the most important — stereopsis and motion parallax — are fundamentally triangulation based.

Active triangulation techniques use a projected light source, often laser, to create one side of the triangle, and the viewing axis of an optical detection means to create the second side. The separation between the projector and detector is the baseline.

A fundamental issue for all triangulation-based approaches is that their ability to estimate range diminishes with the square of the range being measured. This may be contrasted with TOF approaches, which have essentially constant error over their operating range.

Field-Based Approaches

Whereas TOF and active triangulation techniques employ the wave propagation phenomena of a particular energy form, field-based approaches make use of the spatially distributed nature of an energy form. The intensity of any energy field changes as a function of distance from its source. Moreover, fields often exhibit vector characteristics (i.e., directionality). Therefore, if the location of a field generator is known and the spatial characteristics of the field that it produces are predictable, remote field measurements contain information that may be used to infer distance from the source.

An interesting distinction between field-based approaches and wave-based approaches is that the former, although they employ energy fields, do not rely on the propagation and conversion (and concomitant losses) of energy. That is, they may employ stationary fields, like those generated by a magnet or static charge. Such fields encode position information by their very shape. Sound and light, although having a wave nature, can be exploited in the same manner as stationary fields because of their distancedependent intensity.

Field-based techniques must confront some basic issues that limit their range of application. First, the characteristics of most practically exploitable fields are typically influenced by objects or materials in the vicinity, and it is not always possible to ensure that these influences will remain constant. Second, the variation of fields through space is highly nonlinear (typically inverse square or inverse cube), implying

that the sensitivity of a measurement is strongly affected by proximity to the source. Notwithstanding these concerns, devices have been developed and are available that perform very well in the situations for which they are intended.