If the input is a ground referenced (single-ended) signal, the signal is connected to S+ and signal ground is connected to S-. Alternatively, a differential signal such as from a bridge sensor can be input across the S+ and S- pins.
The inputs have a 1K series resistor to limit input current to a safe level.
Gain of the AD620 is adjusted using a 100K potentiometer (marked 104). The advertised gain is 1.5x to 1000x and a lower resistance equals a higher gain. Turning the pot CW increases the gain.
The output of the AD620 is passed through one of the two LM358 op amps configured as a unity gain buffer. The LM358 can source about 30mA and sink 20mA. The output of this buffer is available on the pin labeled VOUT.
Zero Offset Adjustment
The other half of the LM358 is also setup as a unity gain buffer to feed the Vref input of the AD620.
The input of the LM358 has a 10K potentiometer (marked 103) and series 1K resistor tied between the V+ and V- power rails. The potentiometer adjusts the voltage input to the LM358 and the output is fed into the Vref pin on the AD620. This allows any offset to be adjusted out or if desired, a positive or negative offset can be adjusted in. Turning the potentiometer CW increases the offset in a positive direction.
To set the offset, the S+ and S- pins are shorted together and the 10K zero offset potentiometer is adjusted until the voltage at VOUT measures 0V or the desired amount of offset.
Module Connections
The module has inputs on one end and outputs on the other. These can be used to connect wires or header pins can be soldered in depending on the application.
1×4 Input Header
VIN = Module power (3.5 to 10V)
GND = Ground for module power
S- = Signal Input (negative connection)
S+ = Signal Input (positive connection)
1×4 Output Header
V- = Negative voltage output from 7660
GND = Ground
VOUT = Signal Output
GND = Ground