Tester, what is it and how to choose the best one?

November 2, 2021

tester , also known as multimeters, is a handheld meter used to measure electrical voltage, current, resistance, and other values. The testers come in both analog and digital versions and are useful for everything from simple tests, such as measuring battery voltage, to troubleshooting and complex diagnostics.

They are one of the tools of choice for electricians to troubleshoot electrical problems in motors, appliances, circuits, power supplies, and wiring systems. DIYers can also learn how to use a tester to make basic measurements around the house.

A tester can be a portable device useful for basic troubleshooting and field service work, or a benchtop instrument that can measure with a high degree of precision. The testers are available in a wide range of features and prices.

Digital testers are now much more common due to their lower cost and higher accuracy, but analog multimeters are still preferable in some cases, for example when monitoring a rapidly varying value.

Newer digital testers have advanced to the point that they can measure extremely small differences or fluctuations. Experts point out that although some testers test higher voltage ranges, it will be less possible to detect smaller changes in these higher ranges.

Next, we will talk about the tester, its functions and much more. That, like the speedometer or voltmeter , cannot be missing in any laboratory. Join us!

What is a tester?

A tester is an electronic tool used to measure voltage, amps, and resistance across circuits. By connecting two wires to different parts of an electrical system, professionals can use a tester to detect voltage and resistance levels, or changes in electrical currents. This tool is also known as a volt-ohm meter or volt-ohm-milliammeter.

Digital testers long ago replaced analog needle-based meters due to their ability to measure with greater precision, reliability, and higher impedance. Fluke introduced its first digital multimeter in 1977. Digital testers combine the testing capabilities of a single task: the voltmeter, to measure volts, ammeter, and ohmmeter.

They often include several additional specialized features or advanced options. Technicians with specific needs, therefore, can look for a model aimed at meeting their needs.

Test leads are flexible, insulated leads that connect to the DMM. They serve as the conductor of the element being tested to the tester. The probe tips on each wire are used to test circuits.

The terms counts and digits are used to describe the resolution of a digital tester – how well a meter can make a measurement. By knowing the resolution of a tester, a technician can determine if it is possible to see a small change in a measured signal.

Example: if a tester offers a resolution of 1 mV in the 4 V range, it is possible to see a change of 1 mV (1/1000 of a volt) while reading 1V.

Tester functions

The testers are capable of many different readings, depending on the model. Basic testers measure voltage, amperage, and resistance and can be used to check for continuity, a simple test to verify a complete circuit. More advanced multimeters can test all of the following values:

  • AC (alternating current) voltage and amperage
  • DC (direct current) voltage and amperage
  • Resistance (ohms)
  • Capacity (farads)
  • Conductancia (siemens)
  • Decibels
  • Work cycle
  • Frequency (Hz)
  • Inductance
  • Celsius or Fahrenheit temperature

How to use the Tester

The basic functions and operations of a tester are similar for digital and analog testers. The tester has two cables, red and black, and three ports. The black wire connects to the “common” port. The red wire connects to any of the other ports, depending on the desired function. After plugging in the leads, turn the knob in the center of the tester to select the appropriate range and function for the specific test.

For example, when the knob is set to “20 VDC,” the tester will detect a DC (direct current) voltage of up to 20 volts. To measure smaller voltages , you need to set the knob in the 2V or 200mV range. To take a reading, touch the pointed bare metal end of each wire to one of the terminals or wires to be tested.

The voltage will be read on the tester. The testers are safe for use on energized circuits and equipment, as long as the voltage or current does not exceed the maximum rating of the tester. Also, you must be careful never to touch the bare metal ends of the tester leads during an energized test because you may receive an electric shock.

Parts of a tester

The face of a digital tester generally includes four components:

  • Display : where you can see the measurement readings.
  • Buttons : to select various functions; Options vary by model.
  • Dial (or rotary switch): to select primary measurement values ​​(volts, amps, ohms).
  • Input jacks : where the test leads are inserted.

Types of tester

Analog Tester

An analog tester is based on a micro ammeter, a device that measures amperage or current, which has a needle that moves on a graduated scale. Analog testers are less expensive than their digital counterparts, but it can be difficult for some users to read accurately. Also, they must be handled with care and can be damaged if dropped.

Analog testers are generally not as accurate as digital meters when used as a voltmeter. However, analog testers are excellent at detecting slow voltage changes because you can see the needle moving on the scale. Analogue testers are exceptional when configured as ammeters, due to their low resistance and high sensitivity, with scales up to 50 µA (50 microamperes).

Tests Digital

Digital testers are the most commonly available type and include simple versions and advanced designs for electronic engineers. Instead of the moving needle and scale found on analog gauges, digital gauges provide readings on an LCD screen.

They tend to cost more than analog testers, but the price difference is minimal between the basic versions. Advanced testers are much more expensive. The digital tester generally better than analog in voltmeter function, due to increased resistance of digital. But for most users, the main advantage of digital testers is the highly accurate, easy-to-read digital reading.

Tester resolution

The resolution of a tester is the smallest part of the scale that can be displayed, which depends on the scale. In some digital testers it can be configured, and higher resolution measurements take longer to complete. For example, a tester that has a resolution of 1 mV on a 10 V scale can show changes in measurements in 1 mV increments.

Tester accuracy

The absolute accuracy is the measurement error compared to a perfect measurement. Relative precision is the error of the measurement compared to the device used to calibrate the tester. Most tester datasheets provide relative accuracy. To calculate absolute precision from the relative precision of a tester, add the absolute precision of the device used to calibrate to the relative precision.

The precision figures must be interpreted with care. The precision of an analog instrument generally refers to large-scale deviation; a 30 V measurement on the 100 V scale of a 3% meter is subject to a 3 V error, 10% of the reading. Digital meters generally specify accuracy as a percentage of reading plus a percentage of the full scale value, sometimes expressed in counts rather than percentage terms.

Sensitivity and care of the tester

When used to measure voltage, the input impedance must be very high compared to the impedance of the circuit being measured; otherwise, the operation of the circuit may be changed and the reading will also be inaccurate.

The sensitivity should not be confused with resolution of a meter, which is defined as the lowest signal change. Whether it is voltage, current, resistance, among others, which can change the observed reading.

Tester charging voltage

Every ammeter connected in series in line, included in a current range, has a certain resistance. Most multimeters inherently measure voltage and pass a current to be measured through a shunt resistor, measuring the voltage developed across it.

The voltage drop is known as the load voltage, specified in volts per ampere. The value may change depending on the range set by the meter, as different ranges generally use different shunt resistors.

Tester probes

This material can use many different test probes to connect to the circuit or device under test. Alligator clips, retractable hook clips, and pointed probes are the three most common types. Clamp probes are used for widely spaced test points, such as surface mount devices. The connectors are attached to flexible, well-insulated cables terminated with appropriate meter connectors.

Tester security

Most testers include a fuse, or two fuses , which will sometimes prevent damage due to current overload in the higher current range. For added safety, test leads with integrated fuses are available. A common mistake when operating an instrument is to configure the meter to measure resistance or current, and then connect it directly to a low impedance voltage source.

Dr. Loony Davis5
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Born and raised in Brussels in an English family, I have always lived in a multicultural environment. After several work experiences in marketing and communication, I came to Smart Water Magazine, which I describe as the most exciting challenge of my career.
I am a person with great restlessness and curiosity to learn, discover what I do not know, as well as reinvent myself daily, someone who is curious about life and wants to know. I enjoy sharing knowledge.
This is my personal project but I also collaborate in other blogs, it is the case, the most important web on water currently exists in the US, if you are interested you can read my articles here.

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