theuerkorn's Full Review: Bosch DLR165K Laser Rangefinder Kit
The evolution of the tape measure finally offers good alternatives and the user has the choice between relatively inexpensive ultrasonic units (albeit with laser pointer) and a more costly true laser measurement. Consumer grade ultrasonic measurement is a rough estimating tool at best where one has to double check the result to make sure the measurement didn't pick up any other surface than the intended one. Sound deadening materials in fact are practically unmeasurable and short distances pose similar issues. Lasers appeared a bit expensive until the limitations of the ultrasonic device became hindering and the laser devices became more affordable.
Bosch?
Well, frankly I first looked at the Stanley product line, but the TLM100 is too inaccurate with +/- 1/4 inch, while the TLM200 gets closer with +/- 1/8 inch and a bit more comfort in provided calculations. The flag ship TLM300 offers an impressive +/- 1/16 inch accuracy and a lot more calculation power but for a proud price.
The Bosch DLR165K, on the other hand, offers the accuracy of the (3x more expensive) Stanley TLM300 in a smaller package but also minimal calculations like the TLM100. In the end, the price slightly more than the TLM100 made the Bosch an excellent choice when trying to use the device for precision work (which I wouldn't recommend the TLM100 for).
DETAILS
Design: [***--] Generally, the DLR165K is a box with a display and a few buttons, not much to get excited about even if it has a waist. The display is large enough for most eyesight and the buttons are clearly marked but lack tactility since they're the typical blister switches without a well defined shape. The (red) measurement button is for use similar to a remote control, though it may be more practical to have it on the side. The Blue color makes sure one recognizes the heritage (Bosch), but it also makes it a bit harder to locate the small device where a brighter color like Orange or Yellow would be more beneficial but not essential.
Accuracy: [*****] Above all, accuracy is for me the most important factor for a replacement or rather supplement for the standard tape measure (which I still use in many cases). So the provided +/- 1.5 mm (1/16 inch) is a typical value and currently on par with much more expensive precision devices. The maximum allowable deviation is rated at +/- 3 mm. Accuracy was the single most important argument for me to purchase the DLR165K! The pin point accuracy of the laser is a huge plus over and above ultrasonic measurement and even rivals traditional tape measures at least in places that are hard to measure. Accuracy goes down a bit when using the extension. Further, there is no user accessible calibration to improve accuracy. Repeatability is excellent and within only occasional variations of the last decimal place.
Usability: [****-] The square design with over-molded elastomer grips fits surprisingly well in the user's hand when held like a remote control. Unfortunately that's not how you would measure against a wall and that's when the button placement becomes a bit cumbersome. Audible feedback to signalize a successful measurement is limited to the clicking sound of an internal relay (not very loud). This along with the lack of display back lighting is the biggest problem when using the DLR165K in a typical construction site environment. The laser can be turned on "permanently" as a pointer which makes it a lot easier to discuss remote structures.
Reliability: [*****] The sturdy design successfully presents a rugged image and I have no indication of a mechanical failure so far. On the measurement level, the laser is (surprisingly) independent of materials. Exceptions are highly reflective material (to the degree of flat mirrors) and highly transparent material (windows). The latter is interesting though since the device's sensitivity is able to pick up a signal reflected from a target behind a window despite the involved reduction and scatter caused by the glass. Most building materials (including black granite) are very reliable targets. Most matte surfaces can be hit in a wide range of angles and still return reliable measurements. (Virtually impossible with the ultrasonic units!)
Range: [*****] Unlike ultrasonic measurement devices, the laser allows to measure much closer and the Bosch goes as short as 2 inches (50 mm). The long range heavily depends on the reflective quality of the target surface. It can reach to an impressive 165 ft (50 m) which would be a good argument in its favor as one would need a fairly big tape to measure that far. Needless to say that ultrasonic device don't apply since they typically reach to only a third of that.
Speed: [****-] Depending on distance and reflective material, Bosch gives up to 4 second for a single measurement before time-out (failure). However, most targets take less time to be reliably measured and complete within half a second or less. Continuous measurement is an option and reduces the number of times for pushing buttons -- if that concern outweighs the reduced battery life. Applications may be limited to "walk offs" and similar quick assessments. Of course now you need to be aware that you're wielding a Class 2 laser (< 1 mW).
Calculations: [***--] Not so impressive are the extras in the form of calculations provided by the DLR165K. Aside from standard addition, subtraction and multiplication (via Area and Volume), the only other feature worth mentioning is the Pythagorean theorem (a2 + b2= c2) which calculates inaccessible distances, provided there is a 90 degree angle in there somewhere. A positive is the memory management which checks the added values for compatibility to avoid erroneous operations (i.e. adding area to a volume).
Flexibility [****-] As most devices, the DLR165K can use both ends of the housing (along the axis of the laser) as a measurement reference. A novelty is the "centered" mounting which is compatible with tripod system. Another neat idea is the "swing-out extension" to allow measuring in a corner where the device normally couldn't reach all the way in. However, this is basically a flimsy molded plastic thorn which doesn't exactly improve accuracy. The imperial and metric units (ft / in, decimal ft, and mm / m) should please any preference, though I am not sure who actually uses decimal feet (other than manually calculating square or cubic feet).
Value: [****-] At roughly $120 street price, the Bosch DLR165K provides excellent accuracy with a limited amount of extras. The application is limited to cases where there is a target to bounce off (including optional laser target card). Hence, the traditional tape measure is by no means going to be fully replaced. However, a laser device is an excellent help in measuring to inaccessible points or over longer distance (especially when there is no helper to deal with the second end of the tape). Regardless, home usage is hard to justify unless you got to have the latest gadgets and this one sure fits the bill. (Either way, the ultrasonic devices are often not worth the consideration.)
Limitations: Since this device measures the time it takes to hit a target and the reflected light to return to the sensor, it's obvious that it has to rely on such surface to be available. Very matte surfaces (aside from plush fabrics) are actually less of a problem than mirror finishes (literally). Yet, both mirrors and windows work surprisingly well when striking the glass perpendicular. Since the beam doesn't get scattered much, minor angular deviations will make the measurement impossible unlike opaque surfaces. Further, it's for obvious reasons very difficult to use in free space where no feature to bounce off is available. You won't be able to use it for cutting boards to length as one would have to add a raised edge etc. which then may turn out more cumbersome and potentially inaccurate than a normal tape measure.
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