Digital voltmeter ammeter: how to use it?

In this post, are shown how it works and how to use the digital voltmeter ammeter. The component I bought is the DE-2645-02.

How it works?

Operation of voltmeter and ammeter

The ammeter measures the current that passes through a conductor in a circuit, while voltmeter measures the potential difference or voltage between two points in a circuit.

voltmeter ammeter — The voltmeter must be positioned in parallel with a circuit part, to measure the voltage there. While the ammeter must be in series with the circuit to measure current. Source: BYJU’S.

A real voltmeter, inside the red rectangle, has a very high internal resistance r, in some analysis, this resistance must be considered.

The real ammeter, inside the red rectangle, has a low value resistance, called shunt, whose value depends on range value that desires to measure current.

voltmeter ammeter D'Arsonval meter — In D’Arsonval meters, a mobile coil (orange) is connected to the electrical circuit (grey), this coil is inside a magnetic field generated by permanent magnets (N and S). Therefore, when it receives a current, receives a force, which produces a torque and moves the pointer. The springs (blue) bring to pointer back to initial position, when there is no more current. This type of analog meter only serves for measure direct voltage and current. Source: UFMG.

Digital voltmeter ammeter converts analog values in digital and shows the measurement in a LED display.

The digital voltmeter ammeter

DE-2645-02 model don’t come with a shunt resistor. The maximum current it supports is 10A and maximum voltage is 100V. Other DE-2645-02 parameters are:

Voltage resolution: 0.1V.
Current resolution: 0.01A.
Supply voltage range: between 4.5V and 24V.
Temperature operation range: between -10ºC and 55ºC (14ºF and 131ºF).
Dimensions: 50mm (1.96in) width, 20mm (0.78in) thickness and 31mm (1.22in) height.

The digital voltmeter ammeter has 5 wires. S1 and S2 terminals must be connected to a voltage source between 4.5V and 24V to supply the component. While L2 and L3 terminals are used to measure voltage and current in a circuit. In addition to that, COM wires are already linked inside the circuit.

Installing the component in a linear power source

I have published a post about the linear DC source, in which was installed the DE-2645-02.

Design and assembling of a linear sourceClick here

Complete list of materials:

Socket plug.
Transformer with secondary 12+12V and 600mA.
6 1N4007 diodes or similar.
Switch with 3 terminals and 1 pole.
2 1kΩ resistors.
Red LED.
3 electrolytic capacitors: 1 of 470μF, 1 of 10μF and 1 of 1μF.
300nF or 330nF polyester capacitor.
100nF ceramic capacitor.
LM317.
10kΩ potentiometer.
L7805CV.
DE-2645-02.
Wires.
Terminal bridge.

Although there are electrolytic capacitors, this is the only representation available on Qucs simulator.

In parallel to C1 capacitor, was placed a regulator L7805CV, to provide a constante 5V output to the digital voltmeter ammeter. The 7805’s regulator circuit was the same shown on regulator’s datasheet.