USB Laser Range Finder

LR4 - Precision USB Laser Rangefinder

The LR4 interface board adds a USB port to an off-the-shelf, inexpensive laser distance measurement tool, allowing software to control the rangefinder and automate data collection.

For years scientists, engineers, and experimenters have wrestled with ultrasonic or IR distance sensors that give mediocre results.  The LR4 makes possible high precision, true time-of-flight laser range finder technology in an affordable package.

Range:                           0.1 to 50 meters
Accuracy:                      3mm max / 2mm typical
Interface:                        USB
Power Consumption:       < 200mA (USB bus powered)
Measurement Rate:         0.4 to 2.5 Hz

When attached to a simple Fluke 414D laser measurement tool (available Fry's or for around $125), the LR4 forms a USB attached laser rangefinder ideal for industrial or robotics use.

The laser rangefinders are vastly superior to ultrasonic rangefinders, which suffer from problems caused by their wide beam pattern.  Narrow objects often appear much wider than they are because of the 20 to 30 degree sense angle of ultrasonic.  IR distance sensors aren’t even in the same league as the LR4.  IR sensors, such as those based on the Sharp GP2D12, have limited range (around 3 feet), non-linear output, and are very imprecise.

When you order the LR4 you will receive a kit that includes the two flex cables that are needed to connect the LR4 to a Fluke 414D.

Here’s how it works:

Purchase an LR4 online here.
Purchase a Fluke 414D.
Open up the 414D and unplug the 414D’s LCD display and keypad.
Clip the 414D's battery wires and plug them into the LR4. (no soldering!)
Plug the LR4 in place of the LCD and keypad.

Now attach the LR4’s USB cable to a USB port and begin using your precision range finder.

This video demonstrates the assembly process.

This video shows off some of the features of the older LR3 and new LR4 using the demo software (available below).  The video was made before we designed the LR4, but all of the features mentioned in the video apply to the LR4 because the LR4 is software compatible with our previous LR3 board.

The LR4 is a standard HID (Human Interface Device) class peripheral.  This means that most operating systems have built in driver support for the LR4.  For example, Microsoft Windows allows applications to read data directly from HID devices - no messy drivers to write.

The LR4 supports both continuous and one-shot measurement modes.  While in continuous mode, the LR4 performs up to two distance measurements per second.  Distance data and status information is returned in simple 8-byte packets.

The LR4 also supports a "keyboard emulation" mode which simulates key presses on a keyboard.  This allows the LR4 to "type" distance measurements directly into standard application programs such as spreadsheets and word processors.

Measurement Rate
Fluke's new 414D laser distance meter has much better range (50m) over their previous comparable product, the 411D (30m).  To accomplish this, Fluke has decreased the measurement rate.  Under good conditions the 414D will produce a measurement every 400ms.  If the range to the target gets above 15 or 20 meters, the measurement rate will decrease.  Targets with poor reflectivity such as a dark or bumpy surface will also cause measurement rate to suffer.  The slowest measurement rate that we have seen from the 414D is about 23 measurements per minute or about 0.4Hz.

Reference Software

The LR4 demo software (see download link below) includes two Windows applications, LRDemo and LRSimple, that show how to create software that interfaces to the LR4.  Full source code is included for both of these applications under a BSD style license.  See the license information at the top of each source file for more information.

The LRSimple application is a bare bones Win32 Console app that implements the simplest method to start the LR4 and read distance measurements.  If you intend to integrate the LR3 into a larger custom application, then this source code is the place to start.

The LRDemo application is a full featured Windows MFC application that demonstrates all of the features of the LR4.  It is somewhat more complex than the LRSimple app and probably should be used as a reference when needing to implement more advance features.

A Win32 command prompt app that logs data from the rangefinder to a CSV file.  Each measurement is date and time stamped with millisecond precision.

Demostrates how to work with multiple LR3 devices attached to a single PC.  This app lists all attached LR4 devices along with their serial numbers, then data is collected from each rangefinder and displayed.

Opens all LR3/LR4 devices and logs data from each one in a separate CSV file along with a date/time stamp.


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Purchase an LR4 Interface Board

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Frequently Asked Questions

Feel free to email us ( with your questions.  Here are some that we have heard more than once:

Does the LR4 work with the Fluke 419D Measurement Tool?
No, it does not...yet.  We plan to make available a version of the LR4 that will work with the Fluke 419D, which has a range of 80 meters.

Can I use more than one LR4 attached to a single Windows PC?
Yes.  Each LR4 contains a unique serial number, so it's easy to identify each LR4 in the system.  The reference software (see above) contains a sample app called LrMulti.  This app demonstrates how to use more than one LR4.

I'm planning on using the LR4 with an embedded microcontroller, is there a more simple way to interface than using the USB port?
The LR4 has a logic level serial port - see the LR4 data sheet (above) for details.  You can connect +5V, Gnd, Rx, and Tx to the LR4 and easily interface the LR4 with Arduino, PIC, or any embedded processor that has a serial port.  Note: The LR4's serial port is not a full 12V RS232 compatible interface.  If you are interfacing the LR4 to a standard RS232 port, then you will need to use a MAX3232 type level shifter.

Does the LR4 work under Linux?
Yes.  Since the LR4 is a generic USB Human Interface Device (HID), it will work well with Linux using Linux USB HID drivers that are present in most builds.  Unfortunately we don't have any reference software to demonstrate LR4 operation under Linux, but there are many good Linux USB HID resources on the web.  Here are a couple: