AC/DC Strain Gage Amplifier
for Interfacing Data Acquision Systems - Model P122

Model P122 rackmount style

The AC/DC Strain Gage Amplifier features high gain, low noise, stabilized DC amplification with versatile input switching to permit operation as an AC amplifier. It is intended to provide a signal conditioning interface for data acquisition systems, oscilloscopes and other devices. The large LED display continuously monitors the output and simplifies setup and calibration procedures.

Transducer excitation, balancing circuitry, amplification and filtering are standard features. With appropriate sensors, the P122 can process signals such as pressure, force, temperature and many others. The AC input switch positions provide an excellent interface for EEG, EMG, EOG, ECG and other bioelectric signals.

Some typical applications include multiple channel in-vitro tissue bath studies, cardiovascular measurements, pulmonary mechanics, gut motility studies and many more.

The P122 is designed to take up less than 2 inches of rack space, allowing a complete, powerful data acquisition system to be configured in a minimum of space.

The P122 amplifier must be used with a Grass medical-grade regulated power supply. The power supplies provide highly regulated ▒12 VDC. All models are CSA/UL listed for medical device safety.

Amplification   50 minimum to 100,000 maximum
Amplification Settings   6-position step switch.
Settings of 2,000, 5,000, 10,000, 20,000, 50,000 and 100,000
Vernier Control   Ratio of 40 to 1
Input Selections
DC   For DC bioelectric potentials from electrodes and for interfacing transducers
AC   For AC coupling of bioelectric potentials from electrodes and AC coupling transducers. Time Constants of 0.01, 0.1, 1 and 10 seconds, switch selectable
Input Impedance   1 Mohm, differential
Balance Voltage   ▒200 mV DC, ▒5% accuracy
Coarse Control   3-position toggle switch: x0.1, x1.0, x20
Fine Control   10-turn potentiometer provides 0.1, 1.0 and 20 mV/turn
Drift   Less than 1 ÁV/hr after thermal stabilization
With Grass FT03
Force Transducer
  5 mg/hr (typical)
(cutoff frequencies, -6 dB)
  3000, 1000, 300, 100, 30, 10, 3, 1, 0.3, 0.1 Hz
Line Filter   Notch-type filter (50/60 Hz), switch selectable
Time Constants   0.01, 0.1, 1 and 10 seconds, switch selectable. Corresponding to frequencies of 10, 1, 0.1 and 0.01 Hz
Output Connector   BNC, front and rear panels
Load Tolerance   5 kohms or greater
Maximum Output   ▒5.0 volts
Display   3-digit LED, minimum resolution: ▒10 mV
Set Output   Pushbutton allows output to be adjusted to zero
Noise   10 ÁV peak to peak, referred to input (DC to 3 kHz)
CMR (Common
Mode Rejection)
  20,000:1 (86 dB) at 100 Hz
Physical Size
P122 Rackmount   19" W x 1.75" H x 8" D
(48.3 cm x 4.45 cm x 20.3 cm)
Weight   3.125 lbs. (1.44 kg)
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• Amplification from 50 to 100,000 for processing of a wide range of bioelectric signals
• AC and DC Input extends versatility by providing excitation for transducers and, with convenient switching to AC, supports EEG, EMG, ECG and other signals
• ▒ 200 mV Balance Voltage simplifies transducer balancing and provides precise measurements of offset potentials
• 10 Low Pass filter positions from 0.1 Hz to 3000 Hz plus line filter tailors the bandwidth to the signal and optimize the A/D process
• LED output display shows instantaneous data values and simplifies setup and calibration
• Very low drift; less than 1microvolt/hour minimizes time-consuming rebalancing procedures

Model P122   AC/DC strain gage preamplifier, 19" rackmount cabinet, includes manual (power supply required)
Model RPS312RM   Medical-grade power supply, 19" rackmount cabinet for use with P122 rackmount model
Optional Accessories:
Model F-7IC3/REV1   3-lead input cable, 16-foot length (4.8 m)
Model TAC-7   Transducer cable, 8-foot length (2.4 m) for connection to most Grass transducers