UFI Model 2991
Impedance Converter
Measurement of the electrical signals that precede or accompany most biological events is often difficult. Measurement problems stem mainly from very low signal amplitudes, high source impedances, and vulnerability to power line interference.
The Model 2991 Impedance Converter provides a way around these difficulties. Instead of trying to measure very small voltage changes, the Model 2991 measures the correlated impedance changes. These range from 0.2 ohm for an impedance cardiograph to over 5 ohms for an impedance respiration transducer. Whether impedance changes are due to resistance, capacitance, or inductance variations, or more usually, a combination of these, the Model 2991 converts them into DC voltages. This technical note discusses several novel ways to use physical transducers with the Model 2991.
Model 2991 specifications
- Electrodes: UFI Model 1081FG contoured Ag-AgCl electrode pair or similar
- Input connectors: 5-way binding posts
- Excitation frequency: 75 kHz
- Front-end offset correction: 10-turn balance control
- Input impedance range: 1 to 2000 ohms
- Noise level: less than 5 millivolts peak-to-peak
- Display: Analog meter
- Output impedance: 4000 ohms typical
- DC output level for 0.25% impedance change: 250 millivolts
- AC output level for 0.25% impedance change: 2 volts
- Output connectors: Two BNC, one for DC, one for AC
- Power supply: 9V battery with built-in test
- Plastic case size: 2.5" x 5" x 7" (64mm x 127mm x 178mm)
- Weight: 16 ounces (450g)
- Options: EKG filter to provide respiration and EKG from the same two electrodes -- contact UFI
Download the Model 2991 user manual
Published references to the Model 2991
