This is Digital multimeter circuit using ICL7107. We can modify the dc digital meter circuit to smart full function multimeter, that versatile available. For example : measure DC voltage, ACV, DC Amp meter, AC Amp meter and as the Ohms meter etc.

Try to build this projects to use it really worth Fully enjoy

**Special Feature**

DC Voltage: 200mV, 2V, 20V, 200V, 2KV, 20KV

AC Voltage: 200mV, 2V, 20V, 200V, 2KV, 20KV

DC Amp: 200uA, 2mA, 20mA, 2A, 10A

AC Amp: 200uA, 2mA, 20mA, 2A, 10A

Ohms meter: 200, 2K, 20K, 200K, 2M, 20M

**DC voltage measurement**

**Figure 1 DC voltage measurement**

In Figure 1 the schematic diagram of this project. Of course, the easiest way is used as the DC voltage meter circuit.

The characteristics of the circuit That can measure voltages up to 200mV. We can be applied to measure the voltage range higher. As circuit is shown in table 1

**Table 1 is shown in the resistance at various ranges.**

Note: We may choose resistors in both formats. For the very high voltage measurement. It is necessary to use the external high voltage probe.

Note: R3=100K ; R4=10K

**DC current measurement**

Next take a look at the simple DC Ammeter circuit is Design appropriate determine the resistance in parallel with the input of the digital meter only.

The principle to calculate the resistance is The voltage caused by the flow of current across the resistor in each range is maximum up to 200mV as show in Figure 2

In Figure 2 is a circuit that is designed to have a range of up to 5 range. For the high current measurement 2 Amperes, Should the input separately, because the contact of switch that can not withstand currents.

Diode D1, D2, overload protection is provided for the input.

Note: R2= 90 ohms, R3= 9 ohms

**AC voltage measurement**

We can design the AC voltage measurement circuit. By add the AC to DC converter circuit that has the together relationship as show in Figure 3.

**Figure 3 the AC voltmeter circuit**

The AC voltage is measured to reduce voltage same the DC voltmeter circuit. Then fed to the AC to DC converter circuit by IC1 and accessories in Figure 3.

VR1 serves as a tune to the correct voltage reading.

**AC current measurement**

The same principle applies to the DC voltmeter circuit. We can be applied to the AC ammeter by adding the AC to DC converter before as show in Figure 4

**Figure 4 AC current measurement**

**Ohms meter**

advantaged that our digital meter better the regular meter. The reading was accurate, and can also be used to measure the resistance of 0.1 ohms or less, such as high as 10M easily, by the circuit connection as shown in Figure 5.

**Figure 5 the ohms meter circuit**

The digital meter module in Figure 1-5 We have shown for the legs of the circuit ICL7107. Compared to the legs of the modules to Easy to write all the circuits. The ROH pin is the output reference voltage at middle leg of the horseshoe-shaped resistor

**Figure 7 the full circuit diagram of digital multimeter**

In Figure 7 is a circuit work perfectly by show PCB layout and the components as show in Figure 8, which can be used to create a user-friendly way.

**Figure 8 the pcb layout and components layout**

**Parts you will needs.**

IC1____TL071__Operational Amplifiers – Op Amps JFET Input Low Noise

IC5____LM7805____Standard Regulator 5 Volt 1 Amp 3 Pin 3+ Tab TO-220

IC3____CD4049____CMOS Hex Inverting Buffer/Converter

IC2____CD4066___Quad Analog Switch/Multiplexer/Demultiplexer

IC4____ICL7107 or ICL7106____Analog to Digital Converter Single Dual Slope 0.003k SPS 3 1/2 Digit LED 40-Pin PDIP

LED 7 segment or LCD display

More Switches please read in text

**Resistors tolerance: 1%**

R1,R26__________________10M 0.5 watts

R2,R25,R30,R33,R36,R38___1M 0.5 watts

R3,R15,R24______________100K 0.5 watts

R4,R19,R20,R23___________10K 0.5 watts

R5,R22___________________1K 0.5 watts

R6______________________110 ohms

R7______________________1K 0.5 Watts

R8_____________________100 ohms 0.5 watts

R9_____________________10 ohms 0.5 watts

R10____________________1 ohms 1 watts

R11,R12,R13,R14_________0.1 ohms 2 watts

R16____________________3.3K 0.5 watts

R17,R27________________2.2K 0.5 watts

R21____________________100 ohms 0.5 watts

R28____________________270 ohms 0.5 watts

R29____________________47K 0.5 watts

R32____________________ 5K 0.5 watts

MKT capacitors

C14______33pF 63V

C15______330pF 63V

C16______0.0039uF 63V

C11______100pF 63V

C10______0.1uF 63V

C9______0.01uF 63V

C8______0.47uF 63V

C7______0.22uF 63V

**Electrolytic capacitors**

C5,C6_____470uF 16V

C13________10uF 16V

**Diodes**

D1-D4_____________________1N5408

D7,D8,D9,D10_______________1N4001

D5,D6,D11,D12,D13,D14,D15___1N4148

**Switch see in circuit and PCB layout**

## Digital voltmeter circuit »

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## Salim Khan

16 Feb 2015Awesome, Thanks.

## Ehsan

27 Jun 2015hi ,ex me can you explain more or upload a video i can’t understand this

for example on part in schematic not join to another pars and if i right count , we most use 11 switches so please to explain your diagram whit video thank u and ex me for my bad language

## momename

28 Jun 2015Hi Ehsan,

You can send me email.

Thanks.

## Ehsan

29 Jun 2015thanks for answer

my email: [email protected]

## Ehsan

7 Jul 2015hi momename please send me a video from your project or a pdf file for more explore

thx for your answers

## khava

2 Sep 2015i need help with building the AC ammeter of 50 hz and i have to use leds to display my values

## Alex

10 Jan 2016hello ,can you explain me more, i don´t understand the unions with the switches

Thanks

## Alex

10 Jan 2016how many ic2 i need, and why one of them has pin 16?

## jon

4 Feb 2016Hello, what model of LED display is used here? I am looking at the schematic and It is saying LA601VA, but I cannot find any information on that model. Will something like the UN4043-13 or LFD5221-20/A-PF work just as well? Thoughts?

## belsin

29 Feb 2016sorry I need more detail about this please help me brother

## belsin

29 Feb 2016sorry I need more detail about this please help me brother send pdf or video to [email protected]

## amrita patil

2 Nov 2016what is need of ic cd4049 in this circuit?

## Sujata Made

4 Nov 2016Please send me EAGLE design(pcb design) and tell me more about power supply used….email id:[email protected]

## craig

8 Dec 2016This circuit is awesome. I was planning on building a simple voltmeter but now I am going to give this more complex version a try. Thanks!

## Asmaa

19 Nov 2017Mr have u become able to build it ???

I saw another digital voltmeter but using 3162 and unfortunately i could not find that Ic

## Jean

11 Dec 2017The IC 2 has 14 legs, the bilateral switches will not work properly because wrong pinning, and diodes 9 a,d 10 are not mounteg at the pronted circuit..

als the lay-out is blurry.

Please in the future publish something working or don’t

grts,

Jean