Hardware

ATI Nano17 setup

This guide is intended to replicate the setup for measuring fingertip forces which I've used for the past 8 years. The setup below costs about $15000 US dollars (~£10k), so is easily within reach for most funding applications and startup budgets. This setup, along with a 3d printer (I have an Ultimaker 2), should be all you need to measure fingertip forces in a wide range of contexts.

My lab has:

2*NANO17-E Transducer with Strain Relieved Cable. I always have purchased transducers with the middle (25) calibration. 

These plug in to an interface board via the multi-prong connector at the back. Newer model have a plug for a power supply.

Each of the interface boards outputs, through a giant black wire, to a National Instruments USB-6343 DAQ device with screw terminals (32 analog inputs, 500 kS/s, 16-bit resolution, ±10 V. NI 781439-01) .

You can wire your interface boards into this particular DAQ as follows:

First strip back the big black cable a bit to give you some room to work with. Then, with mini wire strippers, strip back the jacket on the small wires to leave ~0.5cm of the inside exposed. Then wire them up as follows:

The first batch of wiring (1-21) is for the first transducer, and occurs in the first 2 leftmost sets of ports on the DAQ. Make sure you take note of which wires are solid, and which wires have the white stripe running through them - the order matters. The second batch of wiring (33-53) is for the 2nd transducer, if you have one. If you have more than 2 transducers, you need a different DAQ (e.g., this), and this guide will not be quite so helpful (but you can refer to the manual here, which has all the information for you to decode at your leisure).

Some things to note:

Weirdly, you leave a number of wires (orange, orange stripe, silver, white, white stripe, black stripe, silver) unconnected. I don't know why.

Also, if your interface board (the black box which your big fat black cable plugs in to) has a DC socket and plug, then lucky you. If it doesn't (i.e., if you acquired yours 2nd hand) then you need to get the power from your DAQ, and wire the red wire into channel 96, and the red striped wire into channel 82. If you can plug your interface board into the wall, then you don't have do (although I'm assured it won't affect your transducer if you get your power from both sources).

Also, if you want to trigger another device from your DAQ (in my case, motion tracking cameras), you connect this wire up into 31 (output) and 32 (ground). The code attached to this page automatically sends a trigger to anything that's waiting, but it doesn't matter if you don't have anything connected up.

Once you have this all connected up (making sure you use the right screws and follow the wiring diagram), unzip the contents of .RAR on this page into your 'My Documents/Matlab' folder*. If you have the same setup as me (2 force sensors connected that DAQ shown above, and Matlab 2014a), this should be plug and play. 

Each transducer comes with it's own calibration file from ATI (either on CD, or emailed with your order). To work with my code, you need to alter the numbers in the 'calibration34.txt' and 'calibration18.txt' with the ones from your sensors' calibrations. To do this, open the ATI calibration files in notepad/plain text editor of your choice (right click and 'open with'), which will open the file like this:

You need to replace the stuff in the calibration34.txt and/or calibration18.txt with these numbers (the ones from your own file, not the ones above) - this is best done manually rather than copying and pasting, as they files are delineated in different ways.

Some stuff to watch out for:

(1) you need a 32 bit version of Matlab, along with the the signal processing toolbox and the data acquisition toolbox. 

(2) if you have a version of matlab newer than 2013a, you need to dump a particular system file in your c:/windows folder (look in the 'readme' folder in the .RAR for details).

(3) you need to run matlab as an administrator (right click on icon in start menu, and select from menu). This might not be necessary after the first run depending on where you installed matlab, but as a first troubleshooting, run as an admin and see if the error changes.

(4) don't forget the calibration file - if you use the numbers I've included then it will appear to work but your force outputs will be garbage

(5) the name (ID) of your DAQ might be an issue as well - if you run the code and it bumps back a screed of errors which end in: 

"the specified device ID is invalid..." 

then type into the matlab console

daqwinfo('nidaq')

This will give you a load of info about your DAQ, including its name (InstalledBoardIds). Use the name here (mine was 'Dev2') to replace the 'Dev1' on lines 221 and 222 of Forcesensors.m