Micro Ampere Meter: Basics and Its Circuit Diagram

An ammeter (abbreviation of Ampere meter) is a device that measures current, an alternating current (AC), or a direct current (DC). A common feature of an ammeter is the low resistance that limits voltage drop during current measurement.

Milliammeters and microammeters are types of ammeter instruments that measure smaller currents. In our case today, we'll discuss microampere meters. For that reason, we'll define the ammeter, discuss its working principle, and tell you how to use it.  

What is a Micro Ampere Meter?

A microammeter/microampere meter/ microamp meter is an electrical instrument that measures minimal current levels (average reading in microamperes). It steps up by measuring the electric current level a conventional multimeter can't accurately measure.

The product details of the microampere meter give you a wide variety of advantages like;

• Micro ampere meters are lightweight and compact, therefore suitable for machinery with less space. It can be a part of larger devices or a separate device.
• Then, a microampere will always maintain its operation and monitoring despite the low or high current.
• Lastly, their covers have good impact resistance hence ensuring durability and protection.

1. Working principle and circuit diagram of a Micro Ampere Meter

A microampere meter uses an active circuit like the one below to complete current tests.  

How the microammeter circuit works 

A microampere has six sensitivity ranges, ranging from 100nA to 10mA. The higher levels ensure calibration since most multimeters lack a low electric current capacity.

R11 and R10 use the meter to implement a 1V FSD voltmeter. For perfect sensitivity, you can also tweak the meter.

1C1 is an operational amplifier with almost 100 times DC voltage gain, and its wiring is in a non-inverting configuration.

Then, C2 minimizes the AC gain, thereby increasing the immunity to stray interference pick-up and stability.

Further, SW1 biases integrated circuit IC1's non-inverting to the 0V rail using resistors in the range of R2 and R7. In other words, you may principally achieve no meter displacement and no output voltage. However, practically you'll need RV1, an offset null control that compensates tiny offset voltages.

Since our circuit requires high input impedance to save more input current, we'll use a FET input op-amp. A FET has a standard input resistance of 15M megaohms.

Finally, D2 and D1 protect the M1 from an overload by ensuring the output voltage of IC1 doesn't reach 1.3 volts.  

How does a microammeter work?

Let's take an example of a moving-coil ammeter;

• The fixed magnets (that should oppose the electric current) cause movement.
• The movement, in turn, causes the centrally located armature, joined to an indicator dial, to turn.
• While turning, the dial above the graduated scale shows the movement of the current amount through the closed circuit.

How do we use the Micro Ampere Meter?

So, to use a microampere meter, we'll need to follow the procedure below.

An ammeter measures electrical current (in amperes/Amp). Current is the rate of electron/charge flow in a circuit. Thus, if we wish to measure the current in a particular course, we'll need to;

• First, disconnect the circuit.
• Then, connect the ammeter in series with your circuit to ensure that electrons flow through both the course and meter. In the selection of meter, it can be a meter dc or an AC ampere meter.
• The positive side of the ammeter should connect to the positive of the other device. The same rule applies to the negative terminals.
• Next, figure out the average current that you'll get by observing the ampere ranges.

Eventually, you'll get your electrical current but lack the resistance and voltage since the meter is part of the circuit.

However, don't connect the meter to a substantial voltage source. The voltage may result in a short circuit and damage the meters. A voltmeter, on the contrary, is favorable since it measures voltage.

Furthermore, have your ammeter connection in series rather than in parallel. A parallel connection will lead to current flow only through the ammeter and not the circuit.  

Summary

All in all, a microampere meter is one of the professional tools you should be having. They accurately measure small currents in devices like thermocouples.

The post has given you a circuit schema of an ampere current meter, including how you can apply it to get a circuit current.

For more information on Micro ampere meters, contact us.