How to Test a Neon Sign Transformer with a Multimeter

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Do you have a business and are looking for ways to draw traffic to it? The decorations you make in your business area and advertisements are essential. Wondering how to decorate your business building? Neon signs are among the best ways to make an advertisement or make your working place attractive and enticing to your customers. 

Neon signs are lightings illuminated from glass tubes containing neon gas and designed into various shapes and designs. Due to their luminous colour, they are suitable for decorations. For the neon gas to light up, high voltage is necessary. For this process to occur, a neon transformer is essential.

What does a Neon sign transformer do?

A neon sign transformer is a transformer that powers the neon signs by converting regular voltage to high voltage. It is a high voltage transformer with two outputs, each being independent of the other. If, for instance, you have a 20kV transformer, it will have two outputs, each of 10kV. The neon transformers contain iron between the secondary and primary windings, thus, giving them an inductance of high leakage. 

The primary purpose of neon transformers is decreasing or increasing the voltage depending on the application of the neon signs. The more neon you want to light, the more voltage needed. The voltage range provided by the secondary windings is between 2 to 15 kV, whereas the range of the line voltage is between 120V to 240V. The current required ranges from 30mA to 60mA. When you vary the voltage supply to the neon tube, the intensity of the lights will also vary.

Pros of neon transformers over other transformers

  • Neon transformers are user-friendly and safe to use. This is mainly because, unlike other kinds of transformers, they use low current. 
  • Most power transformers are good at regulating voltage overload conditions that vary. On the other hand, neon transformers have poor voltage regulation, which makes them limit the current flowing in the neon tubes. Neon lightings require low current.

If you are experiencing the low intensity of your neon lights, then the problem could be the transformer. Therefore, to maintain great illuminating neon signs, ensure you check your transformer regularly. Though there are many devices you can use, a multimeter is the best, most accurate, and the simplest to use

What is a multimeter?

A multimeter is a tool used to measure resistance, voltage, current, and other values in any electronic device. It is also referred to as an ohmmeter. Multimeters are of two types, a digital multimeter, and an analogue multimeter.

Analog multimeter

As the name depicts, this multimeter uses analogue techniques to exhibit measurement readings. An analogue multimeter has a progressed scale and a needle-moving over it. This kind of multimeter is mostly used to detect slow measurement variations.

Digital multimeter

This is an electronic multimeter whose measurements readings display on an LCD screen. It is common because it is small in size and quite easy to operate. A digital multimeter is preferable due to its high accuracy, high digital resistance, and the fact that they are easy to read. 

Nevertheless, digital multimeters are preferable to analogue multimeters. Pros of digital multimeters that makes them better include:

  • They do not have movable parts, thus, making them not wear out quickly.
  • You do not need to adjust them to zero.
  • Some meters are auto-ranging; hence, they cannot be easily damaged when an incorrect range is set.

Despite the above advantages, digital multimeters are quite expensive compared to analogue meters.

Before testing the transformer with your multimeter, there are a few steps you need to follow. 

  1. Visually examine your transformer. One of the common causes of defective transformer is overheating, which leads to the physical deformation of the transformer.
  2. Check the wiring of your transformer. The transformer should have clear labelling of the wiring. Nevertheless, the best way is to get the graphic of the circuit, which is in the instruction manual of the transformer.
  3. Once you already determine the wiring, find the outputs and inputs of the transformer. The electrical input, which is the primary of the transformer, is connected to the first circuit. The other circuit is connected to the output, which is the secondary of the transformer. You should ensure that you label the voltage supplied to the primary and that generated by the output both in the schematic and transformer.

Measuring the voltage of the transformer using a digital multimeter

Using a multimeter to check voltage is pretty simple. Here are the steps you need to follow to attain the voltage of your transformer.

  1. Switch off the power supply to the transformers circuit and remove any coverings to have access to the transformer’s circuit.
  2. Connect the probes of your multimeter to the primary of the transformer.
  3. Set your meter to AC volts and then select the range. It would be best if you chose the highest range, usually 200V, and can make adjustments later. iv. Connect your meter to the power and turn it on.
  4. Examine the voltage in the centre tap.
  5. Do your reading on the LCD and record it.
  6. Repeat the above procedure to check the secondary of the transformer.
  7. If you do not get the correct voltage value, then you need to replace your transformer.

Checking the transformer’s continuity 

The importance of checking continuity in a transformer is to determine the resistance in the output and input coils. Therefore, you will know if either of the wires of the coils has a breakage. Below are the steps to follow when testing continuity using your multimeter.

  1. Disconnect the transformer completely.
  2. Set your meter to ohms mode (Ω) to measure resistance.
  3. Attach the input probes to the two terminals of the primary coil.
  4. Make and record your reading.
  5. Repeat the above steps on the output probes.
  6. If you get an infinite or high resistance, it means that your circuit has a breakage, and therefore, you need to replace your transformer.


In conclusion, regular testing of your transformer is something you need to prioritize if you want to keep your neon lights illuminating well. And from the steps listed above in the article, it is clear that the testing process is pretty straightforward. It is a DIY thing.

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