DT 9812 / DT 9818 Medical Waveform-Generator
Digitimer Stimulator DS5 Control Unit
Compared with Digitimer Constant Current Stimulator Model DS7A (CE), delivering with each Trigger a rectangular shaped
Stimulus, the new Model DS5 (CE) works like an „Amplifier“. The DS5 delivers a Bipolar Constant Current Stimulus at the
output which is precisely proportional to the analog voltage applied to the DS5 input. The DS5 was designed for the "Nerve
Excitability/Threshold Tracking Studies" by Prof. Bostock from the University College Sobell London and his "Qtrac"
Software. But the DS5 in combination with the Medical Waveform Generator DT 9812 DT 9818 is also a high quality
alternative to the standard Stimulator DS7A.
The DT 9812/DT 9818 Medical Waveform-Generator creates with a minimum of effort any bipolar stimulus shape to
control the DS5. The combination Medical Waveform-Generator and Stimulator DS5 allows the user to operate the DS5
like the Standard Stimulator Model DS7A. For more DS5 and DS7A details see www.digitimer.com.
The DT 9812 / DT 9818 Medical Waveform-Generator is a combination of two parts:
1.: Control Software MWG V2.7 or higher with a set of basic waveform templates.
2.: BNC Box DT 9812 (Software Trigger) or DT 9818 (Hardware Trigger) with Analog Output to control the DS5 Stimulator.
When using a new or different hardware box refer to Data Translation GmbH first to enable the use of the software.
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1. DT 9812 DT 9818 Hardware: BNC Box with DAC and Input- Output- USB- Connector
DT 9812 BNC Box Software Trigger
DT 9818 BNC Box Hardware Trigger without Delay
Note: The Delay between "Start" (Trigger TTL-IN) and ANALOG OUT (Waveform) depends on the processing
time of the PC/Laptop, only "TTL sync OUT" starts exactly when the waveform is present at Waveform OUT.
"TTL sync OUT" can be used to start additional devices e.g. a recorder. The Hardware Box is connected to
the Laptop/PC by USB cable.
Only Model DT 9818 allows Hardware Trigger without any delay, see note1) on page 5.
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2. Control Software MWG V2.7 and Basic Waveform Templates
The Control Software MWG V2.7 or higher allows the following functions:
2.1 Definition of a single Stimulus (Pulse Form and Pulse Duration, Amplitude, Polarity).
The following Waveform Templates (Pulse Shapes) are standard:
Square wave (positive/negative); increasing ramp and decreasing ramp (positive/negative); triangle and
sine wave. Creating user defined waveform patterns of any shape is possible any time by editing an ASCII
Pattern for example using Excel® (ASCII-File) which can be easily imported into the Control Software MWG
V2.7. Contact Data Translation GmbH for special custom tailored templates.
Medical Waveform Generator
- Pattern Generation -
Medical Waveform Generator
- Main -
2.2 Digital Pulse Program Generator
This feature allows the individual generation of complex pulse train pattern.
2.3 Oscilloscope Function: visualization of DS5 Control signals "Current" and "Voltage"
The DS5 creates two Analogue Monitor Signals (BNC on the DS5 rear side) which are proportional (1) to the
delivered stimulus current and (2) to the source voltage to drive this current. The Oscilloscope-Function
allows the real time visualisation of both signals on the PC screen for an "online Control" of the applied
waveform. Just connect the DS5 Monitor BNC Outputs to the Recording Analog IN, CH0 and CH1.
2.4 Trigger-Function
The Trigger Function (DT 9812: TTL IN; TTL OUT is connected parallel to avoid a BNC T-connector if needed)
allows the start of the waveform generation from a footswitch or TTL Trigger Signal from external devices
(positive going edge, negative going edge on request). The Output "TTL sync" allows exact synchronisation
with external devices like an EMG-Recorder.
Between start (TTL IN) and the start of the waveform (TTL sync OUT) is a short delay depending on the
speed of the PC processor. Only Model DT 9818 allows Hardware Trigger without any delay, see 1) page 5.
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3. Principle of Operation:
The pulse shape is defined by a sequence of digital ASCII digits (numbers) called "Template", created and
stored on the Laptop/PC. The Template is either automatically generated using the "Automatic Waveform
Generation" or individually designed using Microsoft Excel or any other text software containing a list of
numbers each representing one sample of the waveform Voltage (e.g. 5.02=5.02V). This information is
transferred via USB into the Digital/Analog Converter (DAC) in the DT 9812/9818 Hardware BNC Box. The
DAC unit converts the digital signal into the analog waveform voltage required to make the DS5 generate a
stimulus current for the patient. A set of standard templates is provided with the software.
4. Patient Safety
Non MDD Devices
Medical Product (CE)
USB Optical Isolator
The medical grade USB Opto Isolator (optional)
realizes an additional patient safety layer to
connect "non MDD" devices (Laptop/PC) to
"MDD" devices (Digitimer DS5) by isolating the
ground potential. (Galvanic isolation protection
is 4KV).
This means the normal ground connection
between Laptop/PC and DS5 is isolated and
separated.
Note: In case no USB Isolator is used the same effect of patient safety is accomplished by connecting all
devices (DS5, Labtop/PC including all peripherals, Monitor, Printer, RJ45-LAN) to a "Medical Grade MDD
Certified Safety Isolating Transformer (CE)". In this case too it is guaranteed that the higher leakage current
of the non-MDD devices cannot flow directly to the MDD devices coming too near to the patient.
Please also note the DS5 Output is perfectly isolated from the DS5 ground connection. Therefore it is
acceptable to keep the DS5 when connected directly to a PC/Laptop without any isolator away about two
meters (2m) from the patient to avoid unsafely touching the DS5 housing and the patient at the same time.
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5. Specifications:
5.1 BNC Box connections
"ANALOG OUT" (Waveform): sampling rate 50 kHz (200µs), to control the Stimulator Digitimer DS5.
"TTL sync" (Out): sync pulse generated with the presence of the analog waveform at the output (see note1).
"RECORDING ANALOG IN", "CH 0" - "CH 3" (4x Analog Input): sampling rate 50 kHz (200µs), to convert and record
the two DS5 Signals "Stimulus Current (mA) and Voltage (V)" for visualization on the PC Monitor.
"Trigger" ("TTL in"): for external starting the Waveform Generation. ("TTL out" is connected to "TTL in").
"USB Connector": to connect the BNC Box to the Notebook/PC.
When using a new or different hardware box refer to Data Translation GmbH first to enable the software.
5.2 Generation of a single Stimulus
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•
•
•
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Pulse Form
Pulse Form
Amplitude
Polarity
Duration
Standard:
Square wave; increasing ramp; decreasing ramp; sine wave form
Individual:
Import individual generated pulse form file (ASCII template, EXCEL)
"Waveform OUT" range 0 - ±10 V
Standard:
positive/negative square wave, increasing and decreasing ramp, sine wave
DT 9812/9818: any value (range 50 - 2000µs)
DS5: depending on the selected safety limits
5.3 Digital Pulse Generator
Definition Pulse Sequence, "Level 1" (one Train):
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Frequency range 0 - 500 Hz
Number of single pulses
Definition Pulse Sequence," Level 2" (looping of "Level 1" Pulse Train)
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Train frequency range 0 - 500 Hz
Number of train repetitions
Example: Pulse Program: 5 x 100 Hz for 1s each, Inter stimulus Interval (ISI) 10s (0.1Hz).
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Pulse sequence "level 1" (Train): Frequency: 100Hz; number: 100; Duration: 1s
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Pulse sequence "level 2" (Loop): Frequency (Train): 0.1Hz; number: n=5
5.4 Oscilloscope Function 4x "RECORDING ANALOG IN, CH0 - CH3"
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•
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Simultaneous display of two analog DS5 Control Signals, one representing stimulus current the other stimulus voltage
and/or additional external signals.
Start (Trigger) signal recording
All channels may be stored and retrieved
6. Note1): Model DT 9818: Hardware Trigger without delay
Using Model DT 9818 instead of Model DT 9812 enables hardware triggering without any waveform delay caused by the PC
processing time. For more details please contact HW MedicalProducts Wiesbaden.
Designed and manufactured by:
Data Translation GmbH, Im Weilerlen 10, 74321 Bietigheim-Bissingen,
Daniel Schmidt, +49(0)7142/9531-0, sales@DataTranslation.de, www.DataTranslation.de.
For sales information, user specific topics and Digitimer DS5 questions contact HW MedicalProducts Wiesbaden
For Model DT 9812 and Model DT 9818 Hardware/Software details please contact Data Translation GmbH.
Status: 11.05.2011
DT 9812-9818 Medical Waveform-Generator for Digitimer DS5 V7 engl.docx
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HW MedicalProducts - Consulting and Sales
Helmut Wehking, Neuberg 1-b, 65193 Wiesbaden, Tel: +49-611-185 1944, Fax: -46
helmutwehking@wehking-med.de www.wehking-med.de