Review By Dean Bielanowski  Ryobi Website -


Ryobi SW109T

Measure Tech Plus Stud Sensor

By Dean Bielanowski

Whether you are setting up shop, hanging a heavy picture or just need to know the location of a wall stud, then a stud sensor almost becomes a necessity if your rooms or shop are covered with drywall, or similar material and the studs are not visible. You could knock on the walls and listen for the hollow and solid rebound sounds but this is often not terribly accurate.

Stud sensors are made by many different companies and some are better than others. I have found many of the cheaper varieties are just not accurate enough and can even give false readings if you have your fingers anywhere but on the top of the unit.

Today we will take a look at Ryobi's high-end Stud Sensor, the SW109T Measure Tech Plus.

Measure Tech Plus

As the name suggests, this device is more than just a stud sensor. It also includes a laser measuring device, and other associated features we will discuss further on, but for now, let's examine the stud sensing function and basic form of the tool. As you can see from the images in the right hand column, the SW109T features an LCD display rather than LEDs that you might find on cheaper units. The LCD display will display the results for each feature of the unit when in use. It runs on one common 9V battery and comes with printed instructions - the battery is included! It ships in a blister-type pack.

Stud Sensing
The SW109T can detect wooden/metal studs up to 38mm deep. Stud sensors basically work by detecting the differences in density/capacitance between a solid material and and absence of such material. On the left lateral side of the unit is a yellow button. To use the stud sensing feature, you need to push and hold this button in while slowly sliding the stud sensor across the wall. If you release the button, the unit will turn off. This is a battery saving feature of the unit. It eliminates any possibility of leaving the tool turned on and hence, draining your nice new battery. It is a slight inconvenience to have to hold the button in during use, but it wasn't really a problem or limiting issue for me... I'm just mentioning it so you, the reader, are aware of how it is used. When on and sliding the unit across the wall, the LCD screen provides the feedback to the user. The LCD readout in stud sensing mode mimics an ascending bar graph (using horizontal lines). As the sensor begins to detect the edge of a stud, the bar lines begin ascending upward. Once the edge is fully detected, the LCD screen displays the word "EDGE" and a constant audible sound emanates. At this point, you should place a mark on the wall to show the edge of the stud.

To find the other edge, move the unit across to the other side of the perceived stud location and begin scanning the wall moving inward toward your first mark. Here you are trying to find the other edge of the stud. Finding the second edge works in the same manner as finding the first edge. The bars will begin to display as you approach the edge and fully display with audible alarm once the unit has fully detected the solid stud edge. At this point place another pencil mark. The center of the stud will naturally now be in between these two marks. Accuracy-wise, it has worked 100% for me and I have used it successfully on more than a dozen times recently located studs for various fixings, including locating ceiling rafters for installation of the HyLoft Overhead Storage System we recently installed in the shop. It helps to know the direction your rafters are running if using it for that application. It certainly is much more accurate than my "el-cheapo" Stanley unit which has been less than effective previously. There are some materials that the measure tech plus will not work so well with... These include ceramic tiles, carpeting and padding and materials with certain amounts of metallic compounds, such as some wallpapers or paints. Nothing more to say for this feature. I am very happy with the performance of the SW109T in stud sensing mode.

Measuring Function
This nifty function of the machine utilizes a laser beam to measure distances and heights. It is an extremely fast way of measuring a room for example, or measuring the distance to a solid object from any point. It has a range of 0.6 meters up to 15 meters. In addition, the unit can also add measurements together, or multiple measurements to provide square and cubic area measure results. You can switch between units of measurement (feet or meters) so its good for whatever form of scale you are accustomed to. You press the "+" and "x" buttons simultaneously to switch between measurement units.

The basic laser measurement is accomplished by using the "READ" button on the SW109T. If you press it once, it will send out a laser beam from the bottom of the unit and provide a measurement on the LCD screen to whatever object the laser beam has been reflected off. You need to keep your eye on the target to ensure the laser beam hits the object you wish to measure the distance to. Alternatively, you can receive real time measurements if you hold the READ button down, which emits a constant laser beam, allowing you to position the beam exactly on your target and then read your measurement. This ensures you get the most accurate result. Speaking of accuracy, the laser measuring function is most accurate over short distances. As the distance increases, the variation in accuracy can widen. At 6 meters for example, the variation can be as wide as 76mm, which is substantial, although this limit is the widest variation. I found the variation was only around 10-15mm over a 6 meter range when I double checked the laser measurement against a standard tape measure. Accuracy can depend on a number of factors, including the density of the material the laser is rebounding off. The laser measurement is taken from the top end of the SW109T to your target. The printed leaflet manual provides all the information and instructions you need for using all functions and features of the unit.

You can also use the unit as a laser pointing device, if you have a need to do so. Note however, that lasers can be dangerous (maximum output of the SW109T laser is less than 5mW - Class IIIa laser) and should not be pointed at anyone, and you should never look directly into a laser beam, for obvious reasons.

Addition and Multiplication
The SW109T allows you to add and multiply values obtained by the laser measure function. This is useful if you wish to work out the total distance of two or more singular measurements (can add up to 999m) or multiply to figure out the square or cubic measurement of a room for example. Measuring the cubic area may be useful for selecting an air conditioning unit size suitable for the room space and the square measurement might be useful for determining how much paint you need to cover a wall etc. To use these functions, you simply take your first laser measurement, then hit the "+" or "x" button, take your second laser measurement and then again hit the "+" or "x" button, depending on your needs. The result will be displayed on the LCD screen, along with the last recorded distance. In addition, the number of measurements added or multiplied so far will be displayed. This is a handy feature, particularly for renovation or home improvement work.

I'm pretty happy with the performance and results of the SW109T. In stud sensing mode, it is very accurate and you know you can rely on it to accurately find studs and rafters behind drywall or similar sheeting materials, which means less missed studs and less holes in the wall to fill later! The laser measure features are a handy tool to get fairly accurate measurements of rooms, or distances to objects, however, I wouldn't rely on it if you need very precise measurements over longer distances. It is more accurate over shorter lengths. I'd recommend this unit for its accuracy in stud detecting alone... the laser features are an added bonus.

This unit may only be available in Europe, UK, Australia and New Zealand. A Ryobi unit with similar functions as the SW109T is available in the "The Works Cordless Combo Kit" available throughout the USA and Canada.

The SW109T retails for around AUD$70.00

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Ryobi SW109T Photos
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The SW109T MeasureTech Plus Stud Sensor

The four primary function buttons. It seems the "READ" button is upside down, however the laser function works in the reverse direction as the stud sensing feature.

Ascending bars mean a stud edge is approaching...

Note fully ascending bars and the word "Edge" is now visible
(it actually blinks) We have found the edge of the stud. Repeat the process on the other side of the stud to find the second edge. Middle of stud is in between two edge marks.

The projecting laser beam from the bottom of the unit.

Here we have the current measurement reading (bottom right), the total combined reading so far (top right) using addition mode and the total number of measurements taken so far (bottom left).

Switched measurement units to feet and inches. Top value shows cubic feet calculation.

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Reproduction in any form prohibited with express prior written permission. Copyright 2005