AD620 Microvolt/Millivolt Signal Amplifier Module with Zero Calibration

Specifications

• Main Amplifier Chip: AD620A

• Voltage Converter Chip: HT7660

• Offset Op-Amp: LM358

• Power Supply (VIN): 3~10VDC

• Signal Inputs: S+ (Positive), S- (Negative)

• Outputs: Vout (Amplified Signal), V- (Negative Voltage Reference)

• Tuning: 2x 3296 Potentiometers (Gain and Zero Offset)

• Dimensions: 32mm (Length) x 22mm (Width)

Downloads:

• AD620 Instrumentation Voltage Amplifier Module -Instruction Manual

Key Applications and Projects

• Digital Scales: Amplifying the weak differential output from a strain gauge load cell so an Arduino can accurately calculate weight.

• Biomedical Sensors: Building DIY ECG (Electrocardiogram) or EMG (Electromyogram) circuits to read tiny electrical impulses from muscles or the heart.

• Industrial Sensor Interfacing: Boosting signals from long cable runs or low-output thermocouples to prevent signal degradation before reaching the main control board.

Unlock New Capabilities (Project Evolution) The Custom Smart Scale: Move beyond basic blinking LEDs and build a practical measurement tool! Wire a 5kg aluminum load cell to the S+ and S- inputs of this module. Supply the board with 5V from an Arduino Uno. Use a multimeter to adjust the top calibration potentiometer until Vout reads exactly 0V with no weight on the scale. Place a known weight on the scale, and adjust the bottom magnification potentiometer until you get a strong, readable voltage. Feed Vout into the Arduino's analog pin, add a simple OLED screen, and you have built a highly accurate, custom digital scale from scratch!

PACKAGE INCLUDED

• 1 x AD620 Voltage Amplifier Module

• 2 x 4-Pin Male Headers (Unsoldered)

FREQUENTLY ASKED QUESTIONS (FAQ)

1. What is the main purpose of this module? It is designed to take extremely weak electrical signals (microvolts or millivolts) from sensors and amplify them into a larger voltage range that a standard microcontroller can easily read.

2. What is the input power requirement? The module requires a DC power supply between 3V and 10V connected to the positive and negative power supply pins.

3. What does the HT7660 chip do? The HT7660 is a charge pump voltage converter. It takes your positive input voltage and flips it to generate a negative voltage rail internally, which is required for the AD620 to operate properly around a zero-volt baseline.

4. What is the V- pin on the output side used for? This is the Negative Pressure (-Vin) output. It provides access to the negative voltage generated by the HT7660 chip, which you can use as a reference or to power other dual-supply op-amps in your project.

5. What is the difference between S+ and S-? These are the differential signal inputs. The AD620 amplifier measures the difference in voltage between the S+ and S- pins, rather than measuring a single pin against ground.

6. How do I adjust the amplification (gain)? You adjust the magnification (gain) by turning the brass screw on the top blue potentiometer.

7. How do I remove the baseline offset (Zero Calibration)? You can calibrate the zero offset by turning the bottom blue potentiometer. Short the S+ and S- pins together to simulate a zero-input state, measure the Signal Output (Vout) pin with a multimeter, and slowly adjust this potentiometer until the output voltage reads exactly 0.00V.

8. What is the LM358 chip used for? The LM358 dual operational amplifier works in conjunction with the calibration potentiometer to buffer and inject the zero-calibration offset voltage into the AD620's reference pin.

9. Are the header pins pre-soldered? No, the module includes two loose 4-pin male headers. You will need a soldering iron to attach them to the board.

10. What are the physical dimensions of the board? The printed circuit board measures 32mm in length and 22mm in width.

11. Can I use this with a 3.3V microcontroller like an ESP32? Yes. You can supply 3.3V to the power supply pins. Just ensure that you tune the magnification potentiometer so that the maximum Vout signal does not exceed your microcontroller's 3.3V analog input limit.

12. Why do the potentiometers say "3296"? "3296" is the standard component code for this specific style of multi-turn precision trim potentiometer, as printed on the side of the blue housing.

13. Does this module work with load cells? Yes, it is exceptionally well-suited for load cells. A load cell is a Wheatstone bridge that outputs a differential millivolt signal, which connects perfectly to the S+ and S- signal inputs.

14. What do the exposed silver pads on the bottom do? The bottom of the board shows the through-hole solder joints for the two 3296 potentiometers.

15. Is this board suitable for high-frequency AC signals? Instrumentation amplifiers like the AD620 are generally optimized for DC or relatively low-frequency AC signals (like biological data or mechanical strain). They are not designed for high-frequency RF or fast audio amplification.

16. Which specific instrumentation amplifier chip is used? The board utilizes the AD620A chip for high-precision signal amplification.

17. How many connection pins are located on the input side (J1)? The input side, labeled J1, features four connection pins: Power Supply +, Power Supply -, Signal Input S-, and Signal Input S+.

18. How many connection pins are located on the output side (J3)? The output side, labeled J3, features four connection pins: Negative Pressure Output (V-), GND, Signal Output (Vout), and GND.

19. Can I power this module with a 12V supply? No, it is not recommended. The maximum rated input for the power supply is 10VDC. Supplying 12V may damage the onboard components.

20. What is the purpose of the four holes in the corners of the PCB? These are structural mounting holes that allow you to securely screw or mount the module inside a custom enclosure or onto a chassis.