When your sensor is connected to arduino and works fine, after you start the USB_theremin_0.maxpat patch you will see something like usb_theremin_0.jpg. In this patch the object usbsen2 is responsible for interfacing with arduino. In the “numberbox” connected right after “sbapshot~” you will see values about 20000 hz (without any antennae connected). The “multislider” area will be black. 
If you will connect any metal stuff to the antenna plug, the value will go down. 
How to tune the system: 
If you will push the space bar the “key” object with the help of “select” will send “bang” to “offset” abstraction to set so called “zero” point. It will happen in 2 seconds (because of “delay 2000”). Delay gives you time to keep distance from the sensor. 
After that the “multislider” will show you the diagram of your movements in front of the sensor (like on the image) and you will hear the “theremin” sound. 
Normally when the installation is set up, fixed and nobody is staying close to your antenna, you just push the space bar to tune it. 
During the long term exposition I use a special “timer” patch to produce the auto tuning of the installation. I will explain it later. 
The slider “log steepness” permits you to scale the system and to extend the sensitive area as much as possible (top positions of the slider). 
The “velocity” subpatch calculates how fast and in what direction you move.

Step by step instruction: 
The sketch I have sent you can work only with older version of Arduino software. 
Download it here and install: 
http://files.arduino.cc/downloads/arduino-0023.dmg 
Run Arduino. 
From the “File” menu open sensorReader5.pde file from the folder sensorReader5 I have sent you. 
Connect Arduino to USB port. 
Open “Tool” menu. 
Select “board” – Arduino Duemilanove or Nano w / ATmega328 
Select “Serial Port” – /dev/cu.usbserial-..... 
Click the left most “verify” button in the top menu. 
Wait a bit. 
The program should tell you “Done compiling” and write in white font “Binary sketch size: 2970 bytes (of a 30720 byte maximum) 
In case of the announcement in red font there is some mistake. 
If everything fine, click “upload” button (second from the right). 
Wait. 
In a little while the program should tell you “Done uploading”.

Sending you updated collection of patches. 
USB_theremin_0.maxpat – the easiest theremin patch to test the sensor. 
USB_theremin_1.maxpat – the classical single antenna theremin. 
USB_theremin_2.maxpat – a kind of previous patch. 
USB_scaleplayer_x1.maxpat – the patch to play scales by means of the internal MIDI synthesizer. 
USB_SFPlayer_x1.maxpat – the patch which plays a preloaded sound file which starts and stops at some adjustable distance. 
USB_GRAIBS1_x1.maxpat – the granular synthesizer, controlled by the proximity sensor. 
USB_GRAINS2_x1.maxpat – the granular synthesizer, similar to the previous one, sensitive to the velocity of movement which controls it’s volume. 
If you want to locate the sensor far from the computer, the best solution is to solder a small extra circuitry (receiver1.gif). In this case you can use some good enough power supply (any voltage between 8 – 12 v.) or just the 9 v. battery. And 5v. you can get from USB or Arduino. 
This circuitry is located near the computer. The sensor is connected by the long cable (up to 30 m.) which is connected to the battery plug of the sensor. The ground wire comes to the GND pin of the sensor and the signal wire comes to the battery 9v. pin. The sensor gets power and sends the data via the same wire. 
Similar way of connection via a sound card is on the photo t-sensor+audioin_long5_660.jpg 
And of cause you can locate the battery near the sensor and connect it the same way we did during the first testing. Perhaps the data cable can be 5-7 m. long. But the battery will be empty in 1-2 days. 
In all cases makes sense to put the sensor into the strong plastic box to avoid any external influences (sensor052_box.jpg).