ICL7107 Digital Ammeter Kit DIY Module DC 5V 35mA 70.6x3 9mm Kits DIY Amp Current MeterOOTDTY100% Brand New and High Quality Circuit Principle:AMM-TE ammeter is mainly composed of ICL7107, power circuit, voltage reference source, input circuit and display circuit.1.ICL7107 is a BCD type A/D integrated conversion chip, its internal components; Linear gain, analog switch, oscillation, display driving, etc.2. The power circuit is divided into positive power and negative power. The positive power is introduced by filtering J2, c8. The negative is composed of R8, Q1, L1, C6, C7, D2, D3 and ZD1, which generate a voltage-5V is input through the chip 26.pin.3. The reference voltage source is composed of R1, R2, VR1, R9, U2. The 36-pin is the input pin of the voltage reference. Adjust the VR1 potentiometer to make the 36-pin voltage to be 100mV.4. The input circuit consists of J1, R5, R6, and C3. When the current of the circuit to be measured passes through R5, it will generate a voltage across R5. This voltage will be input to the 31-pin chip through R6 current limit and be processed, C3 is the input voltage filtering capacitor.5. The display circuit is composed of DS1-DS4, D1, D4, 4 digital lamps can be driven directly by the chip. R10 is the current limiting the DS1-DS3 resistance of digital decimal tubes. Finished product debugging:1. When connected to DC 5V (please note the polarity), the digital tube-shaped will display-.000 or. 000, that's normal.2. Use a multimeter to measure the voltage between the 36-pin and 35-pin chip, and adjust the VR1 100mV potentiometer.Key points voltage reference value:1.Chip 1-pin and 21-pin: 5V.2.Chip 36-pin and 21-pin: 100mV,3. 26-pin and 21-pin ship: -5V. Specification:Material: PCB + Metal + Plastic Type: Digital Ammeter Kit Panel Size: 79x44mm / 3.11 x 1.73in Mounting Size: 71x39mm / 2.8 x 1.53in Quantity: 1 PcElectricity Parameters:Operating Voltage: DC 5V Working Current: 35 mA Accuracy: 1mZ Measuring Range: 0 - 2A Over-Range Indicator: 1/-1 Primacy Display Display Color: RedQuantity: 1 Set Note:Due to the difference between different monitors, the picture may not reflect the actual color Item. Package Included:1 Set x Set with Digital Ammeter