Overview
Researchers currently operating GRASS polygraph systems for isolated tissue bath studies can cost-effectively modernize their data acquisition infrastructure by migrating to the iWorx IX-RA-834 digital recorder while retaining their existing GRASS force transducers. This technical note outlines the system compatibility, hardware configuration, and integration steps required for a seamless transition.
Background
GRASS polygraph systems have provided reliable analog recording capabilities for decades in physiology research, particularly in tissue bath applications measuring force generation in isolated smooth and skeletal muscle preparations. However, traditional polygraph instruments present several limitations:
- Limited data retention: Analog recordings on paper or proprietary media are
difficult to archive and search - Poor data portability: Analog formats lack standardization and are incompatible
with modern analysis software - Hardware obsolescence: Repair and replacement parts for legacy GRASS
equipment are increasingly difficult to source - Integration constraints: Analog systems cannot readily interface with modern
laboratory information systems or computational analysis platforms - Manual analysis requirements: Force measurements require manual digitization
or proprietary software conversion
Modern digital data acquisition systems address these limitations while preserving the ability
to use existing transducer hardware investments.
System Overview: IX-RA-834 Data Recorder
The iWorx IX-RA-834 is a versatile, multi-channel digital data acquisition system specifically designed for physiological research applications including isolated tissue and organ studies. Key specifications relevant to tissue bath applications include:
Hardware Specifications:
- DIN8 Transducer Inputs: 4 channels (A5-A8) with bridge amplifier interfaces
Add an IA-400D for additional 4 transducer inputs - Input Range: ±10 VDC, 16-bit resolution
- Excitation Power: ±5 VDC @ 100 mA per channel
- Sampling Rate: 200 kHz aggregate across all channels
- BNC Inputs: 4 additional general-purpose channels (A1-A4)
- Stimulation Capability: Low voltage (±15V @ 35mA) and isolated high voltage (0-
1mA @ 100V) outputs - Interface: USB 2.0 connection to Windows or macOS computer
- Software: LabScribe data acquisition and analysis platform with extensible module library [2]
Compatibility: GRASS Force Transducers with iWorx DIN8 Inputs
GRASS force transducers, including the widely-used FT-03 series, produce low-level differential
voltage outputs proportional to applied force. The IX-RA-834’s DIN8 transducer inputs (A5-A8) are specifically designed to accommodate such instruments through bridge amplifier architecture.
Signal Characteristics:
GRASS force transducers operate with the following electrical characteristics:
- Output impedance: Low impedance differential output from internal Wheatstone bridge
- Typical sensitivity: 5-10 mV/gm of force (depends on transducer configuration)
- Frequency response: Suitable for quasi-static tissue bath measurements up to
several hundred Hz - Noise characteristics: Low drift and noise suitable for force measurement
applications - The IX-RA-834’s DIN8 bridge amplifier inputs are optimally configured for these signal levels.
Integration: C-DIN-GRASS Adapter Cable
iWorx provides adapter cables specifically designed to connect legacy GRASS transducers to modern digital recorders. The adapter cables are available in two configurations to match the connector gender of your existing GRASS transducers:
Cable Options Grass Adaptor Cable
C-DIN-GRASS-M: Grass Male to DIN8 Male Adapter
- 5-foot cable
- Compatible with GRASS FT-03 male connectors
- DIN8 male connector for direct attachment to IX-RA-834 inputs
C-DIN-GRASS-F: Grass Female to DIN8 Male Adapter
- 5-foot cable
- Compatible with GRASS FT-03 female connectors
- DIN8 male connector for direct attachment to IX-RA-834 inputs
Specification: When ordering, you MUST specify the gender of your GRASS transducer
connectors (Male or Female) to ensure correct cable configuration.
Integration: Stimulation
For tissue bath experiments that require electrical stimulation, the HCS-100 high current stimulator can be added to the iWorx recording system. The HCS-100 provides high-output stimulation for organ bath and tissue bath applications, allowing researchers to drive stimulation protocols from the iWorx ecosystem.
System Configuration for Tissue Bath Applications
Hardware Setup
The integration process requires:
- iWorx IX-RA-834 data recorder
- C-DIN-GRASS-M or C-DIN-GRASS-F adapter cable(s) for each GRASS force transducer
- Existing GRASS force transducer(s) (e.g., FT-03 series)
- HCS-100 as a 4-channel, 50 V stimulator with up to 500 mA total output
- Standard 12 VDC power supply (included with IX-RA-834)
- Computer with Windows or macOS operating system
- USB connection to IX-RA-834
- Tissue bath apparatus (unchanged from existing setup)
Channel Configuration
The IX-RA-834 provides four DIN8 transducer channels (A5-A8), allowing simultaneous recording from up to four independent GRASS force transducers in multi-chamber tissue bath experiments. Each channel includes:
- Dedicated ±5VDC excitation power for bridge-based transducers
- Programmable gain via input resistor selection (allows adaptation to different GRASS
transducer sensitivities) - 16-bit digital conversion at 200 kHz aggregate sampling rate
- Differential instrumentation amplifier for noise rejection
Gain Configuration
The DIN8 inputs use bridge amplifier circuits where gain is programmed by placing a resistor between pins 5 and 8 of the DIN8 connector. The C-DIN-GRASS cables set the gain of the amplifier to x100. The LabScribe software allows straightforward configuration of units settings for each channel.
LabScribe Data Acquisition Software
The IX-RA-834 is controlled entirely through LabScribe, iWorx’s comprehensive data acquisition and analysis platform.
Data Acquisition Features:
- Real-time multi-channel recording (up to 128 channels with iWire expansion)
- Configurable sampling rates and channel filtering
- Simultaneous visualization of multiple channels
- Event marker annotation capability
- Live signal calibration and verification
Data Analysis Features:
- Post-experiment signal analysis and filtering
- Custom analysis modules including force measurement, peak detection, and kinetic parameter extraction
- Force-time integral calculations for tissue contraction work
- Comparative analysis across multiple experimental protocols
- Export to standard formats (text, Excel) for further processing
- Migration Workflow: Transitioning from GRASS Polygraph
Setup
Hardware Assessment
Identify all GRASS force transducers currently in use, noting:
- Number of transducers
- Connector gender (male or female) on FT-03 transducers
- Typical signal ranges and sensitivities
- Existing chamber configurations
- Document existing experimental protocols and recording parameters
System Acquisition and Setup
- Launch LabScribe and verify hardware detection
- Configure active channels (A5-A8 for GRASS transducers; additional BNC or iWire channels if needed)
- Set appropriate gain values for each GRASS transducer based on sensitivity specifications
- Apply desired analog filtering (low-pass filtering at 100-200 Hz typical for tissue bath work)
- Configure sampling rate (1-10 kHz typical for force measurements; system supports up to 200 kHz)
- Create recording templates matching your existing experimental designs
Validation and Calibration
- Perform system calibration using known force standards (e.g., calibrated weights)
- Record test experiments with existing tissue preparations
- Compare force measurements and noise characteristics with legacy GRASS recordings
- Validate LabScribe analysis modules produce equivalent results to prior analysis methods
Advantages
Immediate Benefits:
- Modern data management: Digital recordings are easily archived, searched, and backed up
- Enhanced analysis: LabScribe provides quantitative force analysis tools unavailable in analog systems
- Multi-chamber capability: Four channels allow simultaneous recording from multiple tissue bath chambers
- Equipment reliability: iWorx systems have active support and readily available replacement components
- Future expansion: iWire serial interface enables straightforward addition of ECG, EMG, or other biopotential measurements
Long-term Benefits:
- Reduced maintenance costs: Digital electronics are more reliable than aging analog equipment
- Integration capability: Digital data integrates with laboratory information systems and databases
- Computational analysis: Easy integration with MATLAB, Python
- Publication standards: Digital data formats meet current journal requirements for transparency and reproducibility
Compatibility Notes
- The IX-RA-834’s DIN8 inputs are designed specifically for bridge-amplifier transducers like the GRASS FT-03 series
- Connector gender must be specified: Ensure you order the correct adapter cable (C-DIN-GRASS-M for male GRASS connectors, C-DIN-GRASS-F for female connectors)
- The 5-foot cable length permits typical bench mounting configurations; longer custom cables are available through iWorx
- Multiple IX-RA-834 recorders can be synchronized via Sync-In/Sync-Out connectors for experiments requiring more than 4 simultaneous force channels
Technical Support
For detailed implementation questions or assistance with system configuration:
Email: [email protected], Website: www.iworx.com, Info: [email protected]
Teaching: (603) 726-1371, Research: (603) 742-2492 x 22
