Home / Circuits / Test equipment circuit diagrams

## Resistance measurement of delicate components

How to measure the resistance of a delicate or sensitive component?

There is a special way of resistance measurement when the component to be measured is very sensitive or delicate.

## How to Measure Beta of a Transistor?

How to Measure Beta of a Transistor? (β / hfe of transistor)

The beta (β) is a characteristic of each transistor. This feature is found in the NTE, ECG manuals, etc. These manuals have a minimum or approximate values of the real values. This means that we do not know the real value of the transistor.

## How to Protect the 500mA Fuse of a Multimeter?

How to protect the 500mA Fuse of a Multimeter?

A very simple circuit that protect the 500mA fuse of a multimeter, due to the high frequency that these are burned.

## Continuity tester using 741 IC

Continuity tester using 741 operational amplifier that operates as a differential amplifier.

A good application for this circuit would be to test welds made on a printed circuit board. It could also be used to test continuity of wires, connections, etc.

## Measuring Low Resistances

Measuring Low or very low resistances

There are cases where the resistance is too low and a direct use of the ohmmeter is not practical. So a special method is needed

## How to Make a Current Flow Indicator?

This Electric Current Flow Indicator gives a visual indication that there is a current flow. Possible applications for this small circuit may be: a battery charger, a voltage power source, etc.

In order to achieve our objective we place 3 rectifier diodes in series, which in turn are in series with the load / battery.

## Op Amp Tester Circuit Diagram

Op Amp Tester Circuit Diagram

Very simple circuit to test 741 op amp or another IC with the same pin configuration. Circuit working explanation

## 555 Timer Tester circuit

555 IC Tester Circuit (PCB)

This 555 IC tester circuit, allows us to make sure that this integrated circuit works properly. This same test can be achieved by operating the 555 as astable multivibrator, but this test does not allow
to observe its operation in detail.

## Audible Logic Probe using the 555 Timer

What is the reason to use an audible logic probe?

Many logic probes use LEDs to visually indicate the logic state of the point under test. This causes the user to have to see the point under test and the LED at the same time.

## What is a Logic Probe?

A logic probe is a simple and inexpensive instrument contained within a pen-like tube. It has 3 LED indicators that show the status of the point under test.

5 DIY Logic Probes

## Audible Continuity Tester

Continuity Tester with Buzzer – Works on live circuits.

This continuity tester with buzzer works on live circuits. Very important, as common continuity testers are used with the power source disconnected.

## Logic Probe with 7 Segment Display

Logic probe using 7 segment display

This logic probe with 7 segment display is designed with TTL technology and does not use LEDs to display the high and low logic levels found in many of the logical probes on the market. The circuit shows the capital letter “H” when there is a logical “1” or the letter “L” when there is a logical “0”.

## Logic probe circuit using CD4001 IC

Logic probe circuit with CD4001 IC

This logic probe circuit is useful for people who needs an instrument to measure the logic levels on digital circuits. This circuit is implemented with CMOS IC technology and is recommended for testing circuits using the same technology

## What is the Wheatstone Bridge Circuit?

The Wheatstone bridge circuit

This circuit  was designed in 1833 by Samuel Hunter Christie (1784-1865). However, It was Mr. Charles Wheatstone who gave many uses to the Wheatstone bridge circuit when he discovered it in 1843.

## Logic Probe using NOT Gates

Logic Probe using NOT Gates (Inverters)

This logic probe using NOT Gates is implemented with three NOT gates, one rectifier diode, two LEDs and two resistors.

## Diode Tester Circuit using 741

How to Make a Diode Tester Circuit using 741?

This diode tester circuit checks if the diode is in good condition and also determines its polarity. To accomplish our goal, we use an 741 operational amplifier (IC1) configured as an oscillator.

## How to Extend the Voltage Range of an Analog Multimeter?

How to extend the voltage range of an analog Multimeter?

In order to extend the voltage range of an analog multimeter, a resistor is used. This resistor is placed in series with the multimeter.

## Logic Probe using two transistors

Two Transistor Logic Probe

This Two Transistor Logic Probe is a very simple circuit that can be implemented using two NPN bipolar transistors (T1, T2) in a Darlington configuration.

•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•