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Amplifiers
Each force plate connects to a SGA6-4 six channel strain gauge amplifier (Figure 1). These have switch selectable gains of 1000x, 2000x, or 4000x for each channel. All channels also have a selectable low-pass filter of 10 Hz or 1050 Hz cutoff. Bridge excitation levels of 2.5, 5, or 10 volts can be chosen. The output signal is rated up to +10V and is suitable for input into an A/D converter. Table 1 shows the specifications of the SGA6-4 amplifier.
Figure 1. SGA6-4 Strain Gauge Amplifier
| Amplifier | |
|---|---|
| Inputs | Six four arm Wheatstone bridges |
| Bridge Excitation | Each channel switch selectable by user. 2.50, 5.00, or 10.00 volts DC ± 0.01 |
| Bridge Balance | Balance potentionmeter for each channel accessible on top cover. |
| Gain | Adjustable on each channel through top cover plate by DIP switches for 1000, 2000, or 4000. May be adjusted 10% from these values with printed circuit mounted potentionmeters. |
| Filtering | DIP switch selectable 10.5 Hz or 1050 Hz 30-dB point for second order critically damped low-pass filter. |
| Output | ± 10 volts into a minimum 2K ohm load. |
| Sample/Hold Control Input | 0 volts (0.8 volts maximum) places the sample/hold amplifiers in sampling mode. Voltages >2 and <15 enable the hold mode on all channels simultaneously. |
| Reference Output | A precision output voltage of the same value as the excitation voltage is provided for calibration of A/D converters. |
| Power Supply | |
| Input | 230 VAC ±10%, 50 Hz. 10 watts typical input power. |
| Output | ±15 volts at 0.25 amp +2.50, or +5.00, or +10.00 volts at 0.25 amp. |