Digital Tape Measure - Page 1
Forum section: electronics / testgear

author: trevwhite
author_rank: Frequent Contributor
timestamp: May 07, 2013, 08:14:36 pm
content: Hi allI found these on Ebayhttp://www.ebay.co.uk/itm/160902446778?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649Has anyone used one? I was wondering if they are any good considering the price is so low? There are a few different ones. I saw some atwww.maplin.co.ukand they were a bit more money but not much. But I dont know if these are as accurate as they state? I have a few measurements to take soon and this would save me a lot of time but only if I get one that actually takes correct measurements.Any help would be greatThanksTrev

author: kripton2035
author_rank: Super Contributor
timestamp: May 07, 2013, 08:27:05 pm
content: it is an ultrasonic model, it is NOT precise. it has a laser pointer, but it measures the distance with ultrasonic sensors.the other models measure effectively with laser beam. they are much more precise (+- 1.5mm) and a longer distance (around 50 m)their price begin around £80 for no brand one.

author: trevwhite
author_rank: Frequent Contributor
timestamp: May 07, 2013, 08:28:53 pm
content: Hi. Thanks for the reply. How well can the ultrasonic version measure? Do you know by any chance?

author: jpb
author_rank: Super Contributor
timestamp: May 07, 2013, 08:43:30 pm
content: I have an ultrasonic one.They are designed for internal measurement of rooms. They are popular with estate agents as they save faffing around with a tape measure - you hold it against one wall and get the measurement to the other. (I am NOT an estate agent, I just bought mine as it was on special offer and thought it might be useful - of course apart from trying it out I never really use it.)Using it outside without a flat wall to reflect the ultrasonic wave off is problematic.So if you work fitting carpets, selling houses or want to measure the height of a very high ceiling then they are useful.Having done this reply, I am suddenly thinking that they might be useful for measuring the depth from the access hole to the level of the oil in my oil tank but as I've not tried this I don't know if it would work.

author: trevwhite
author_rank: Frequent Contributor
timestamp: May 07, 2013, 08:53:28 pm
content: Hi, I just want to measure some rooms properly. It is a pain with a tape measure and was hoping it would be quicker with one of these units as they were only £10 or so. If they are an inch out its no big deal for me.Sounds like the Ultrasonic one might be okay. How repeatable are the measurements? Does it always measure the same for a particular wall?Trev

author: kripton2035
author_rank: Super Contributor
timestamp: May 08, 2013, 09:11:08 am
content: I have both an ultrasonic and later I bought a laser one. never used the ultrasonic anymore !On the face of it, ultrasound has many of the same advantages that a Laser Distance Meter enjoys – one-person / one- handed operation, no need to access the target personally, etc. However ultrasound is intrinsically less accurate, because sound is far more difficult to focus than laser light. Accuracy is typically several centimetres, compared with a few millimetres for laser. And in some conditions, the ultrasound accuracy can be much poorer than the ‘typical’ values.Ultrasound needs a fairly large, smooth, flat surface as the target, so that is a severe limitation. You can’t measure to a narrow pipe, for example. The ultrasound signal spreads out in a cone from the meter and any objects in the way can interfere with the measurement. Even with laser aiming, you can’t always be sure that the surface from which the sound reflection is detected is the same as that where the laser dot is showing. This can lead to gross errors.Range is limited to about 15m, whereas some laser devices can measure up to 200m. Ultrasonic measuring devices may be cheaper, but the cost of their inaccuracies and limitations is far greater.http://www.transcat.com/technical-reference/PDFs/Application%20Notes/cordex-laser-distance-meters.pdf

author: jpb
author_rank: Super Contributor
timestamp: May 08, 2013, 09:32:27 am
content: Quote from: trevwhite on May 07, 2013, 08:53:28 pmI've not used mine for a while and it is at home and I'm at work, but my memory is that the accuracy is probably within an inch for standard sized rooms with a blank facing wall. They are certainly less accurate than laser ones but also much cheaper.According to Bosch the accuracy of their laser device is 2mm and the accuracy of an ultrasonic device is 50mm in 10m (but 10m is a pretty big room).http://www.amazon.co.uk/Bosch-Digital-Laser-Range-Finder/dp/B0033UWLWY/ref=sr_1_1?ie=UTF8&qid=1368004913&sr=8-1&keywords=ultrasonic+tape+measure+accuracyThese laser ones seem a lot cheaper than they were. When I bought my ultrasonic one the laser ones were a couple of hundred pounds or more. Now they are £73 - I feel tempted to get one for no good reason other than it would be fun to have!