14.12.2015|Articles & Video

UNI-T UT391 Laser Distance Meter Review

With each year, technological progress is influencing our day to day and professional lives more and more. Even such a trivial thing as a measuring tape, which is irreplaceable in construction and high precision repair work, has a digital analog. It’s called a laser distance meter and after it had appeared on the market it quickly started to be referred to as a laser measuring tape.

The main advantage of the laser measuring tape over a regular one is that it allows taking quick and easy measurements of quite long distances without the need of assistance from anyone. Moreover, such devices can measure length, height and width of various objects, as well as their area and volume very accurately.

The meter uses a laser diode as a source of electromagnetic radiation to take measurements. There are two methods of measuring distances:

  • The impulse method - measuring distance based on the delay of the reflected signal
  • The phase method – measuring distance based on the phase displacement of the reflected signal as compared to the sent signal

Phase laser distance meters are more accurate than impulse ones. Also, they are easier to produce and, therefore, are a lot less expensive.

Laser distance meter UNI-T UT391
Laser distance meter UNI-T UT391

Today we are going to talk about a member of the family of phase laser distance meters – UNI-T UT391, a model produced by Uni-Trend. This device can measure distances of up to 60 m with measurement precision of 1,5 mm.

The product comes with a small carrying case that can be attached to a belt for convenience. A user manual and 2 AAA batteries are included in the package contents, as well as a small Phillips screwdriver which is used to open the battery compartment.

Laser distance meter UNI-T UT391
Laser distance meter UNI-T UT391

According to the user manual, the keyboard is made of “Super Soft Touch” material which, in real life, turned out to be regular rubber cover. Let’s take a closer look at the keyboard. The CLR/OFF and the big red ON/MEAS buttons have two functions: switching off/clearing the measurement results and switching off/starting the measurement, respectively. Besides those two, UNI-T UT391 has the following buttons: area and volume measurements, continuous and indirect measurements, adjustment of the measuring reference level (from the front or rear edge), data saving, addition and subtraction of the measured values and, finally, the backlight button that also allows switching between measurement units (meters, inches, feet). Although there are quite a few of them, the buttons are positioned very conveniently on the device.

Laser distance meter UNI-T UT391
Laser distance meter UNI-T UT391
Laser distance meter UNI-T UT391
Laser distance meter UNI-T UT391

The device is made of high quality plastic and is very pleasant to the touch. It should be pointed out that the device is assembled very well without any defects.

Laser distance meter UNI-T UT391
Laser distance meter UNI-T UT391
Laser distance meter UNI-T UT391
Laser distance meter UNI-T UT391

The manufacturer has equipped the UTI391 with a small LCD that can display 4 lines of data. There is no difficulty to see the information on the display in natural daylight but under direct sunlight it fades. Looking ahead, though, I have to say that you probably will not want to use the device under strong sunlight anyway. However, working in places with little or no lighting is very convenient thanks to an excellent backlight of the display.

Laser distance meter UNI-T UT391
Laser distance meter UNI-T UT391

The most important part of the device, without which it would be impossible to measure distances, is located on the front edge. This is, of course, the class II laser emitter (635 nm, 1 mV) and the reflected signal receiver. Maximum distance of measurement (which, again, is 60 m in this case) is directly related to the reflecting capabilities of the target surface. In other words, objects with flat surfaces, such as walls, wood constructions and others alike are ideal for such measurements, while objects with convex or uneven surfaces do not reflect the signal that well.

Laser distance meter UNI-T UT391
Laser distance meter UNI-T UT391

Laser distance meters are usually divided into two categories depending on the maximum measurement distance: day to day and professional. The device we are describing today is in the first category. During testing it was observed that when the meter measured long distances outdoors under strong daylight it experienced some difficulties. This serves as additional evidence that the device is in the day to day category. There are no complaints about measurement accuracy, it’s just as stated by the manufacturer – 1.5-2 mm.

Let’s take a closer look at measuring functions of the UNI-T UT391. First of all, a few words about adjustment of the measurement reference level. By default it is set to the rear edge, it can be switched to the front edge by pressing the corresponding button twice. Another miscalculation was made by the manufacturer here, as the default setting cannot be changed. This means that each time the device is switched off the reference level setting goes back to default, i.e. to the rear edge. Taking into account the fact that the device switches off automatically after two minutes this characteristic is not so much a defect as it is an irritating overlook. The same applies to switching between measurement units.

Let’s move on to the actual measurements:

  • Continuous measurement function. In this mode, measurement results are updated dynamically every 0.5 seconds when moving towards the object. Minimum and maximum values (that are also being updated dynamically) are displayed on the first two lines of the display.
  • Addition and subtraction of the results. Every measured value can be added to or subtracted from the previous one using PLUS and MINUS buttons.
  • Area and volume measurement function. After the area/volume button is pressed the first time the area measurement mode is activated, as indicated on the screen. Area calculation is completed in two steps during which the length and the width of the surface are measured and then displayed on the screen. The volume measurement mode is activated by pressing the button twice, until the indicator is shown on the screen. To measure the volume, the same steps should be completed as in area measurements with an addition of the height measurement.
  • Indirect measurement function. In this mode, the meter takes two or three measurements that are necessary for calculation of the object’s height. The laser beam should be pointed at the following points on the measured object: top, middle horizontal, bottom and bottom in the maximum horizontal position.

In conclusion, despite a few miscalculations UNI-T UT391 is a good laser distance meter which is ideal for indoor exploitation.

Thanks to high quality of assembling, the possibility to measure distances of up to 60 m and a wide range of measuring functions UNI-T UT391 is an excellent day to day device that will prove useful in any repair or layout work.

You can buy the UNI-T UT391 laser distance meter in our store.


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