Plexon Stimulator 2.0 User manual

Stimulator 2.0 April 2011
Plexon Inc
6500 Greenville Ave. Suite 700
Dallas Texas 75206
United States of America
Tel: [phone]
Fax: [phone]
E-mail: [e-mail]
www.plexon.com
Stimulator 2.0 April 2011
STIMULATOR 2.0

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Stimulator 2.0
User’s Guide April 2011
CAUTION: THIS STIMULATOR IS NOT FOR USE IN HUMANS
CAUTION: READ THE ENTIRE MANUAL BEFORE ATTEMPTING TO OPERATE THIS EQUIPMENT
IMPORTANT: OBSERVE THE FOLLOWING SEQUENCE DURING ALL EXPERIMENTS:
1. TURN THE STIMULATOR POWER ON
2. LAUNCH THE USER INTERFACE PROGRAM
3. CONNECT THE STIMULATOR TO THE ELECTRODES
4. CONDUCT THE EXPERIMENT
5. CLOSE THE USER INTERFACE PROGRAM
6. DISCONNECT THE STIMULATOR FROM THE ELECTRODES
7. TURN THE STIMULATOR POWER OFF
Plexon Inc Proprietary
The information contained herein is the property of Plexon Inc. and it is proprietary and restricted
solely to assist Plexon Inc. customers.
Neither this document nor the contents may be disclosed, copied, revealed or used in whole or in
part for any other purpose without the prior written permission of Plexon Inc. This document must
be returned upon request of Plexon Inc.
The information contained in this document is subject to change without notice. Plexon Inc.
reserves the right to make changes in equipment design or components as progress in engineering
or manufacturing may warrant.
This user’s guide is PN 14-20-A-13
This user’s guide refers to:
Hardware PN 14-20-A-10-A
Firmware PN 14-20-A-07
Software PN 14-20-A-08
Copyright © 1983-2011 Plexon Inc, All Rights Reserved
® Plexon is a registered trademark of Plexon Inc.
Printed in the United States of America

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Table of Contents
1Introduction..............................................................................................6
2System Requirements ...............................................................................6
3System components..................................................................................7
4Installation................................................................................................8
4.1 Driver Installation ..................................................................................................................................... 8
4.2 Software Installation ................................................................................................................................ 9
4.3 Hardware Installation............................................................................................................................12
4.4 Turning on the power for the first time .........................................................................................14
5Getting Started........................................................................................15
5.1 Overview .....................................................................................................................................................15
5.2 Operational Flowchart...........................................................................................................................16
5.3 Launching the Stimulator 2.0 software ..........................................................................................17
5.4 Creating a burst of rectangular pulses ............................................................................................18
5.5 Verifying the output on an oscilloscope .........................................................................................19
5.6 Compliance voltage and stimulation failure.................................................................................22
5.7 Automatic electrode discharge ..........................................................................................................24
5.8 Arbitrary Waveforms & Complex Rectangular Pulses..............................................................25
5.9 Impedance measurement.....................................................................................................................27
5.10 Working with real electrodes .............................................................................................................30
5.11 Starting stimulation from a digital input .......................................................................................32
5.12 Stopping stimulation ..............................................................................................................................34
6GUI Function Reference ..........................................................................35
6.1 Parameters Edit/Load ...........................................................................................................................35
6.1.1 Edit...........................................................................................................................................................35
6.1.2 Load.........................................................................................................................................................35
6.2 Stimulation Stop/Start...........................................................................................................................36
6.2.1 Stop..........................................................................................................................................................36
6.2.2 Start.........................................................................................................................................................36
6.3 Rectangular Pulse Parameters ...........................................................................................................37
6.3.1 First Phase Amplitude.....................................................................................................................37
6.3.2 First Phase Width..............................................................................................................................37
6.3.3 Interphase Delay ...............................................................................................................................37

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6.3.4 Second Phase Amplitude................................................................................................................37
6.3.5 Second Phase Width.........................................................................................................................37
6.4 Number of Repetitions and Pulse Rate...........................................................................................38
6.4.1 No. of Repetitions ..............................................................................................................................38
6.4.2 Rate..........................................................................................................................................................38
6.5 Arbitrary Waveform Patterns.............................................................................................................39
6.5.1 Fixed Sampling Rate ........................................................................................................................39
6.5.2 Variable Sampling Rate .................................................................................................................40
6.6 Vmon scaling and Z conversion .........................................................................................................41
6.6.1 Vmon scaling (Stimulation mode) ............................................................................................41
6.6.2 Vmon scaling (Z test mode)..........................................................................................................41
6.6.3 Z conversion.........................................................................................................................................42
6.7 Function Stimulate / Function Z test...............................................................................................42
6.7.1 Stimulate Mode ..................................................................................................................................42
6.7.2 Impedance Test Mode .....................................................................................................................42
6.8 Trigger Mode .............................................................................................................................................43
6.8.1 Software Trigger Mode ..................................................................................................................43
6.8.2 Rising Edge Trigger Mode.............................................................................................................43
6.8.3 Level Trigger Mode ..........................................................................................................................44
6.9 Edit/Load All..............................................................................................................................................44
6.10 Start Mode...................................................................................................................................................45
6.11 Monitor Channel.......................................................................................................................................45
6.12 ABORT ..........................................................................................................................................................46
6.13 File Open / File Save ...............................................................................................................................47
6.14 Options: Discharge Mode......................................................................................................................48
6.15 Options: Digital Output Mode .............................................................................................................48
7Input and Output Connectors..................................................................50
7.1 Power In.......................................................................................................................................................50
7.2 Digital In ......................................................................................................................................................50
7.3 USB 2.0 .........................................................................................................................................................50
7.4 Stim Out .......................................................................................................................................................51
7.5 Digital Out ...................................................................................................................................................51
7.6 Current Monitor .......................................................................................................................................52

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7.7 Voltage Monitor........................................................................................................................................53
7.8 Stimulation Cable.....................................................................................................................................53
8Sample Arbitrary Waveform Pattern Files ...............................................54
9Stimulator Limitations.............................................................................55
9.1 Maximum Compliance Voltage Varies with Stimulation Amplitude...................................55
9.2 Power on/off Transients.......................................................................................................................55
9.3 Current Monitor with an Open Circuit ............................................................................................56
9.4 Impedance Test with an Open Circuit .............................................................................................57
9.5 Channel fails to start in Impedance Test mode ...........................................................................57
10 Specifications ..........................................................................................58

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1Introduction
The Plexon®Stimulator 2.0 is a 16-channel constant current stimulator system. It has 16
individually programmable constant current sources that share a common return path. Stimulation
currents may be defined with 16-bit precision up to ±1 mA and delivered with ±10 V compliance.
The graphical user interface makes it easy to define bi-phasic rectangular pulses with micro-Amp
precision and micro-second temporal accuracy. Bursts of pulses repeated at a user defined rate are
also easily configured. In addition, Stimulator 2.0 adds the ability to load arbitrary waveform
patterns from text files.
Playback of pulses and arbitrary stimulation waveforms may be initiated from the GUI or triggered
in response to external digital inputs. Each channel has a dedicated digital input that may be used
in an edge triggered or level triggered (gated) mode to initiate stimulation with microsecond
latency. Each channel also has a dedicated digital output to signal to other devices the precise time
when stimulation is occurring.
The actual current and voltage delivered to any electrode can be conveniently monitored on an
oscilloscope using the standard BNC monitor outputs. A convenient impedance test mode provides
nanoamp resolution and additional filtering and programmable gain for the monitor channel
outputs so that the voltage elicited in response to sub microamp currents may be resolved for
impedance measurement.
Thank you for purchasing this Plexon product. We hope you are pleased with every aspect of it.
Please do not hesitate to contact us if you have any questions.
2System Requirements
A modern personal computer running Windows 7 or Windows XP with a free USB 2.0 port is
required to operate the system.
An oscilloscope is highly recommended for monitoring the actual current and voltage waveforms
during stimulation.

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3System components
When you receive your Plexon stimulator, confirm that you have the following pieces:
1. USB memory with software & drivers Plexon 14-20-A-14
2. AC power cord (7.5 ft)* Volex 17250 10 B1
3. Power Supply Plexon 09-06-A-14-P1
4. DC power cable (6 ft) StockCable R58190A-06
5. USB Cable (2m) Molex 88732-8902
6. Stimulator Plexon 14-20-A-10-A
7. Stimulation Cable Plexon 14-03-A-03
8. Test Board (model electrodes) Plexon 14-04-A-03-A
* International customers: The stimulator power supply has an International Electrotechnical
Commission (IEC) 60320 C14 inlet for AC power (shown below). The AC power cord supplied with
the stimulator has an IEC 60320 C13 connector and a NEMA 5-15 plug compatible with the AC wall
outlets in North America. Users in other regions must supply a power cord with an IEC 60320 C13
connector and a plug that is compatible with the AC wall outlets in the region of use.
1
2
3
4
5
6
7
8

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4Installation
Read the entire installation section before proceeding with the installation. Follow the installation
steps in the order that they are presented. Install the drivers first, followed by the software,
followed by the hardware. Do not connect the stimulator to an electrode implant until you have
read the entire manual.
4.1 Driver Installation
Read the entire Driver Installation section before proceeding with any of the steps.
4.1.1 Browse to the folder \Stimulator\Driver on the USB flash drive and run the program
CDM20802_Setup.exe. On some computers, you will get a warning:
Windows 7: Windows XP:
4.1.2 Click Yes or Run to continue:
A command window opens briefly to display the status of the driver installation and then
closes automatically:
Hint: If you do not see the command window at least briefly then it is quite possible that the
driver installation did not complete. In this case, double click on CDM20802_Setup.exe a
second time.

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4.2 Software Installation
Read the entire Software Installation section before proceeding with any of the steps.
Hint: If you are trying to replace an existing version of the software, you should first remove the
existing version before installing the new version.
4.2.1 Browse to the \Stimulator\Software folder on the USB flash drive
4.2.2 Double-click the file Stim-2_Setup.exe to begin the installation process. On some computers,
you will get a warning:
4.2.3 Click Yes or Run to continue. The welcome screen appears:
If the software is already installed, then the welcome screen gives you the option to repair
(re-install) or remove the software as shown on the right above. If the software is not
already installed, then the welcome screen shown above on the left appears.
Click Next to continue.

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4.2.4 Select the location to install the software:
The default install location for Windows 7 (64 bit) is C:\Program Files (x86)\Plexon Inc\
The default install location for Windows XP is C:\Program Files\Plexon Inc\
Click Next to continue.
4.2.5 You will be asked to confirm that you would like to start the installation:
Click Next to continue.
4.2.6 When the installation begins, it may take a couple of minutes before the progress bar begins
moving across the window. This is especially true in Windows 7:

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4.2.7 Once the progress bar starts moving, the installation completes quickly.
Click Close to complete the software setup.

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4.3 Hardware Installation
Read the entire Hardware Installation section before proceeding with any of the steps.
An oscilloscope is highly recommended for viewing the output of the monitor channels.
4.3.1 Ensure that the power switch on the power supply is in the off position.
4.3.2 Connect the AC power cord between the AC outlet and the power supply.
4.3.3 Connect the DC power cord between the power supply and the stimulator.
You may connect to either OUT 1 or OUT2 on the power supply.
4.3.4 Connect the USB cable between the stimulator and the computer.
4.3.5 IMPORTANT: Turn on the stimulator power and launch the stimulator GUI before
connecting the stimulator to any electrodes.

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4.3.6 Connect the stimulation cable between the stimulator and the test load board. Be sure to
line up the white orientation dots on both connectors.
4.3.7 Connect BNC cables between the monitor channel outputs and an oscilloscope. Monitoring
the current and voltage delivered to the electrode is an essential part of stimulation.

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4.4 Turning on the power for the first time
4.4.1 Turn the power supply on. The six LEDs on the front of the power supply and the one LED
on the front of the stimulator should illuminate.
4.4.2 The first time you turn the stimulator on a “Found New Hardware” balloon will appear in
the lower right hand corner of the computer screen. In Windows 7, the balloon changes
from “Installing device driver software” to “Your device is ready to use”. In Windows XP,
the balloon cycles through several different displays including “Plexon Stimulator”, “USB
Composite Device”, and “USB Serial Converter X” where X is successively A, B, C, then D:
Windows 7: Windows XP:
…
(repeats for USB Serial Converter B, C, D)
…
4.4.3 If the “Found New Hardware Wizard” appears, then the drivers for the stimulator are not
properly installed. Refer to section 4.1 for the driver installation procedure.

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5Getting Started
This section introduces the basic functions of the stimulator guides you through basic stimulator
operation using the model electrodes on the test board. It is highly recommended that you work
through this section before attempting to do any other type of stimulation. Note that you will need
an oscilloscope to see the output of the monitor channels.
IMPORTANT: OBSERVE THE FOLLOWING SEQUENCE DURING ALL EXPERIMENTS:
1. TURN THE STIMULATOR POWER ON
2. LAUNCH THE USER INTERFACE PROGRAM
3. CONNECT THE STIMULATOR TO THE ELECTRODES
4. CONDUCT THE EXPERIMENT
5. CLOSE THE USER INTERFACE PROGRAM
6. DISCONNECT THE STIMULATOR FROM THE ELECTRODES
7. TURN THE STIMULATOR POWER OFF
5.1 Overview
Every stimulation protocol begins with the definition of the stimulation pattern. The stimulator 2.0
graphical user interface (GUI) provides a means for defining bi-phasic rectangular pulses and
bursts of identical pulses that are repeated at a fixed rate. More complicated rectangular
waveforms and non-rectangular arbitrary waveforms may be defined in and loaded from a simple
text file. Once defined, the stimulation pattern is downloaded into the stimulator memory for
playback. Playback can be initiated from the GUI or in response to a digital input to the stimulator
hardware. During playback, the actual current and voltage delivered to the electrode can be
observed on the monitor outputs. Monitoring the electrodes during stimulation is a critical
component of successful stimulation.
In addition to performing stimulation, Stimulator 2.0 also has a special impedance testing mode. In
impedance testing mode, the stimulation pattern is a predefined 1 kHz ±100 nA sine wave that is
automatically loaded into every channel. Playback of the impedance test waveform on particular
channels is initiated from the GUI. The voltage elicited in response to the impedance test current is
then observed on the voltage monitor output to determine the electrode impedance. Variable gain
steps are provided to resolve a wide range of electrode impedances.
The flowchart in section 5.2 presents the basic operational steps for using Stimulator 2.0.

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5.2 Operational Flowchart
Start Stim 2
Software
Function
Stimulate
Rectangular
Pulses
First phase
amplitude
and width
Interphase
delay
Second phase
amplitude
and width
Number of
pulses
Rate
Trigger Mode
Load
Start
Monitor
Arbitrary
Waveform
Load File
Number of
pulses
Rate
Trigger Mode
Load
Start
Monitor
Function
Z Test
Automatically
loads
waveform
Start
Vmon Scaling
Monitor

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5.3 Launching the Stimulator 2.0 software
Make sure the stimulator is connected to the computer and turned on. Then launch the Stimulator
2.0 software by double clicking on the desktop icon. You should see the factory default graphical
user interface as shown in the figure below:
Hint: You may load the factory default configuration at any time by selecting Open from the File
menu and then selecting the configuration file “Factory_Default.stm”. By default this file is installed
in the directory C:\PlexonData\Stim-2\Configuration files.
Note that if the USB cable is not connected to the stimulator or if the stimulator power is turned off
when the software is started then and error message will appear. Likewise, if the USB cable is
disconnected or the stimulator power is turned off while the software is running an error message
will appear and the program will close:

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5.4 Creating a burst of rectangular pulses
For each channel there is a row of channel specific controls and then at the bottom of the interface
there are additional global controls. These controls are described individually in detail in section 6
of the manual. In this section, only the controls required for generating rectangular pulses using
the GUI controls are discussed.
The first step is to configure the stimulation parameters for a single channel. We will start off
configuring channel 1 to generate a bi-phasic rectangular pulse that repeats indefinitely at a rate of
200 Hz.
Examine the controls for channel 1:
The default configuration specifies a single biphasic pulse with a short inter-phase delay. The first
phase is +100 µA for 50 µs, the inter-phase is 0 µA for 25 µs, and the second phase is –100 µA for 50
µs.
To make it easier to see on the oscilloscope, we want to generate a continuously repeating pulse
instead of a single pulse. Locate the “No. of repetitions” control at the right hand side of the row of
controls and type “INF” in the control:
Hint: If the No. of repetitions control is set to “1” and you press the down arrow, the control will
change to “INF”. You can also type “0” in the control and when you click on any other control the 0
will change to INF.
The controls for channel 1 should now look like this:
The next step is to download the stimulation parameters into the stimulator hardware. Click on the
“Load” button at the far the left of the row of controls:
Note that the GUI controls for configuring the pulse parameters become grayed out once the
channel has been loaded. To change the parameters you must go back to “edit” mode.

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Once the parameters for a channel have been loaded you may start the stimulation by clicking on
the “start” button:
The stimulation begins, and because the number of repetitions is set to infinite, the pulses will
continue until the “Stop” (or “Edit”) button is pressed.
5.5 Verifying the output on an oscilloscope
Now examine the current and voltage waveforms on an oscilloscope to see if they make sense. Note
that both the current and voltage monitors output a voltage signal and that there is a scaling factor
that relates what you see on the monitor output to what is happening at the electrode. The scale
factor for the current monitor is 2.5 mV/µA and by default the scale factor for the voltage monitor is
0.25 V/V. That means that if there is a 100 µA current flowing into the electrode from the
stimulator, the current monitor will read:
   
 
Likewise, if the stimulator was applying 1V to the electrode, the voltage monitor would read:
  

The current monitor waveform you see should appear similar to the figure below:
At the beginning of the pulse, the current monitor (IMON) jumps from 0 mV to +250 mV and stays at
+250 mV for 50 µs. Then the current monitor drops back to 0 mV for 25 µs and finally drops to
−250 mV for 50 µs. Considering the 2.5 mV / µA scaling factor on the current monitor these 250 mV
steps represent current steps of 100 µA as expected from our channel configuration settings. The
durations also match our settings.
50 µs
50 µs
25 µs
+250 mV @ IMON = +100 µA @ electrode
–250 mV @ IMON = –100 µA @ electrode

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The output of the voltage monitor is a bit more interesting:
At the beginning of the pulse, the voltage monitor (VMON) jumps from 0 mV to +125 mV, then
linearly increases another 266 mV over the 50 µs duration of the first phase. Considering the
default scaling of the voltage monitor, the voltage at the electrode initially jumps 500 mV and then
increases another 1.06 V over the course of the 50 µs pulse.
The initial jump in the electrode voltage is due to a property of the electrode called “access
resistance”. In order to drive a current I into the electrode, we must apply a voltage V to the
electrode that satisfies Ohm’s law with respect to the access resistance of the electrode:

    
The subsequent rise in electrode voltage during the first phase of the pulse is due to charging of the
electrode “capacitance”. By definition, the capacitance of the electrode relates the voltage on the
electrode to the amount of charge deposited on the electrode:
  

Therefore, the rate at which the electrode voltage changes during the pulse is directly proportional
to the amount of current applied to the electrode and the capacitance of the electrode:

  

  
The change in electrode voltage during the first phase of the pulse is thus given by:
     

The access resistance and capacitance of the model electrodes on the test board are 4.99 kand
4700 pF respectively. Therefore the expected initial voltage jump for a 100 µA current is:

     
VACCESS
VCHARGE
50 µs
50 µs
25 µs
+266 mV @ VMON = 1.06 V @ electrode
+125 mV @ VMON = 500 mV @ electrode