RoadTest: Multicomp Pro Non-Contact Voltage Tester
Evaluation Type: Test Equipment
Did you receive all parts the manufacturer stated would be included in the package?: True
What other parts do you consider comparable to this product?: Ames Voltage Detector - Harbor Freight TackLife VT02 Voltage Detector - Amazon Best Seller
What were the biggest problems encountered?: All quirks are in the sensor technology, not the actual product.
As a person that works with mains voltages regularly, I was quite excited to be selected to roadtest the Multicomp Pro Non-Contact Voltage Tester (MP780053). Having a tool in your pocket that can tell you if a circuit is energized or not is quite handy – especially when it also doubles as a flashlight. I really liked the idea that the tester would beep faster the closer one got to an energized source.
My original test plan was to chart the response curve of the frequency of the beeps to the distance from an energized source. These sources would be an open lug, an insulated cable and an outlet at various mains voltages (120v/240v single phase, 120v/208v three phase and 277v/480v three phase). Alas, the beep response is not directly proportional to the distance. In high voltage mode, there is one threshold. It beeps or it doesn't. In 12V/low voltage mode, there are four thresholds and the beeping does change tempo the closer one gets to the energized source.
*This actually worked out to my advantage as my Arduino based beep detection circuit did not function as intended.
I also planned to check if multiple energized conductors affected sensing.
The first thing I noticed about the Multicomp Pro Non-Contact Voltage Tester when I removed it from the packaging was that it felt like it would survive the job site and my tool box. After unscrewing the flashlight end to install the batteries, I was confident that its IP67 rating was the real deal. I won't be testing that until the very end.
To use the tester, you simply press the power button and release. The tester illuminates the tip with a green LED, turns on a forward facing LED flashlight and beeps once. You are ready to test circuits in the high voltage mode. When you press the power button again, the tester beeps twice and turns off. While the tester is on, one can also select the low voltage mode by holding the [12V] button in. This is a spring loaded button with IP67 protection. Sustained pressing will greatly fatigue the forearms. *** This is the only product feature I would change. *** Make the [12V] button ON/OFF - PLEASE.
The tester has an auto-off feature. After approximately five minutes of not detecting voltages, the tester will turn itself off. It does signal this with the two beep OFF tone. This auto-off also applies to the flashlight. This is an awesome feature for a tool that lives in a toolbox. When the tool is actively used, the tester remains on. During testing, mine remained on for two to three hours at a time. I did change batteries once, but my use case - with little rest in between measurements - was an unrealistically extreme case. Under normal use, the batteries should last quite a while. I did not test to determine how low the batteries can get and still have the tester function. I changed the batteries because I believed that I was getting greater deviation in my reading than before. Again, extreme use case.
As mentioned in the introduction, the Multicomp Pro Non-Contact Voltage Tester has a high voltage and a low voltage mode. The fourth and final detection threshold in low voltage mode is the detection threshold for the high voltage mode. An oddity of the different thresholds is that they have dead band where the circuit can't decide which level it is at. The dead band seems most significant between the initial detection level and the second one. Of course, this is of zero consequence as no normal person is going to advance this tester at a circuit as slow as I did while trying to determine the threshold distance - and the tester always beeped after a second or two.
While not part of the original testing plan, after taking a hundred readings or so, I wanted to know "At what voltage does this tester respond relative to the different thresholds?" This would also tell me the equivalent voltage levels that extended from the energized circuits - or at least the equivalent strength of the radiated electric field. With this knowledge, I might be able to gage the system voltage given the distance at which the tester responds.
When the tester starts beeping for High Voltage at almost three feet from the cable... it also causes you to ask "How much power is radiating into this space that I'm standing in?"
|1 - Slow|
|2 - Medium||19.7v|
|3 - Fast||28.5v|
4 - High Voltage
The test procedure was to touch the tip of the tester to the wire and turn up the voltage on the variable transformer. Record the measured voltage when the tester responded to the various thresholds. Repeat four more times. Average the readings.
The testing showed a much more linear response than I expected. The distance testing appeared to have an exponential component to it, which was more in line with my expectations.
Prior to testing, I expected that the open lug would yield the greatest response distance because there would only be air between the lug and the tester. You will see in later sections that this did not prove itself to be true. While the uninsulated lug presents a greater shock hazard than the insulated cable, it is characteristically the end of a run - and the end of the radiated electric field.
The test setup is pictured below. The panel has multiple transformers, providing the most common US voltages. Testers like the Multicomp Pro often use a capacitive divider circuit for determining voltage and this one behaved accordingly. It responded to the phase to ground voltage levels. This made the 120v/208v three-phase source moot as the phase to ground voltage is no different than the 120v/240v single-phase source. Fortunately for my testing, we also have three-phase center-tapped Delta. For those familiar with this winding configuration, you know to be leery of the phase opposite the center-tap. This is the "high leg"; 208v to neutral/ground.
The other characteristic that validated the capacitive sensing was the difference in readings when I advanced tester along the insulated brace. This was my original plan for taking measurements but the tester sensed at a greater distance than in free air. For safety's sake, I still needed to maintain positive control over the energized lug so this was as close to an isolated lug as I could get. The string helped maintain the measurement so I could grab a wooden ruler and measure the distance.
The first set of readings are with me being as insulated from Earth as I can be. The gloves are Class 0 rated, safe to work on circuits up to 1000 volts. I am also wearing boots with a dielectric sole (advertised at 30kV). Let me add... pushing that little [12V] button wearing high voltage gloves... not fun. This testing method demonstrates the "worse case scenario" where the detector responds at the closest distance. I have opted not to include a chart of the average values used to create the graphs because your mileage may vary. The capacitive divider network depends on so many variables and the numbers create a false sense of accuracy.
This set of readings represents a "best case scenario" with the tester beeping at the furthest distance. To insure the most consistent readings, I wore a ground strap and held the tester with bare hands. The higher voltages were detected further away, but the 120v circuit had similar beep thresholds in both methods.
The test method for an insulated cable was similar to the lug. Testing was slightly easier as the measuring string could be used to pull the cable to the tester. The string also provided a reference to align the tester so it stayed oriented towards the cable. Again, I did not expect this application to give the highest readings but it did. Thinking it through, there is twice the electrical field, so the tester should respond earlier/further away.
During these readings, I again used the gloves and insulated boots. When compared to the isolated lug wearing the same Personal Protective Equipment (PPE), the tester responded at almost twice the distance. While this may seem obvious, this validates that the tester can be used to find opens in wires. It may also assist in finding internally corroded wires / multiple broken strands. While not common, this failure can be tough to troubleshoot.
Soapbox: If you are using piercing probes, stop it. Especially in maritime or vehicle (wet) applications.
In this troubleshooting method, the open part of the wire may still indicate voltage presence but it will be at a greatly reduced level - causing us to have to move the tester much closer to the cable. General fault location identified. Splice here.
This test series again used the ground strap and yielded the greatest distances for voltage indication. Even without using the low voltage mode, the tester gives a decent safety margin.
While one can compare the different charts for the various voltage levels, I thought grouping the readings by voltage would also be beneficial. I chose 120 volts because it is the most common voltage in the US. 208 volts and 277 volts respond similarly. Below is a comparison of the distances to respond for each of the test methods for 120 volt circuits.
This chart clearly shows that using the non-contact voltage tester with bare hands and touching the grounded (Earthed) cabinet will yield a response further from the source. If you want circuit selectivity, insulating oneself may help as detection distances are closer to the source.
Outlet testing is what I most closely associate non-contact voltage testers with. Oddly enough, they have the most difficulty in this application. The extra housing of the outlet impacts the capacitive divider network such that you have to be very close to the energized source for them to alarm - or be in a low voltage mode. Wearing insulated gloves or wearing a ground strap had minimal impact on the response. Even on a 277v/480V outlet, the tester did not respond in high voltage mode until approximately 1/2 inch from the outlet. With the insulating gloves on, the distance was between 3/8ths inch and one half inch.
Outlet build quality revealed itself in testing outlets. The least expensive 120v residential grade outlets required the probe to be inserted into the outlet approximately half the time. The same outlet of a commercial grade would cause the tester to beep within one quarter inch to touching the slot, but did not require insertion to alarm. I attribute this to more copper in the commercial grade outlet.
My buildings have no 120v/240v three-phase, four-wire outlets so I was unable to test those. The 120v/208v three-phase outlets are all 120v to ground so they behaved as the 120v outlets above.
The final question of the roadtest was to determine if multiple conductors affected the distance at which the tester responded. Alas... yes and no. Also, "yes" in low voltage mode and "not really" in high voltage mode.
The Christmas lights (fairy lights) proved to be an interesting display of this. When the lights were coiled but had an open bulb and would not light, the multiple unlit coils responded (high voltage) at a further distance than the coiled section that was lit. The unlit coil responded at about three times the distance (about 3 inches) of the single unlit strand (about 1 inch). I though I would be able to replicate this with an extension cord. Not so much. There was a difference, but it was less than 1/4 inch - within the margin of error for detector orientation angle differences. I could get it to display the difference in low voltage mode (approximately the same 3 to 1 ratio). I also tried adding load to the extension cord to see if this changed anything. What I took away from trying to replicate what I saw with the Christmas lights was more validation that the tester wasn't responding to a magnetic field as do current clamps. Current flow had zero effect on the sensing.
I don't know if there is a practical application for this knowledge given the hot and cold response from the tester. However, in attempting to replicate this experiment with the TackLife... quality of build revealed itself. The Multicomp Pro was consistent and the Tacklife was not.
This was also not part of the original roadtest proposal, but it is a product differentiator. The video sums it up. It's the real deal.
I did open the battery compartment off camera and it was completely dry. I could find no signs of water intrusion at all.
I do not consider the Ames or the TackLife to be of the same quality as the Multicomp Pro Non-Contact Voltage Tester. I owned the Ames model before the roadtest. It has one threshold and one momentary ON button. This is okay for checking outlets at home, but I'll never go back to it for work, when I have to wear voltage rated gloves. I purchased the TackLife tester because it had similar advertised features to the Multicomp Pro, was listed as an Amazon Best Seller and wasn't very expensive. While the advertised features are very similar, the major difference is the Multicomp Pro performs consistently and the TackLife did not. Additionally, the case on the Multicomp Pro is robust. The TackLife might survive the kitchen junk drawer, but there's no way that it's surviving the jobsite or an active toolbox. All three detectors have similar quirks which helped me segregate what is relevant to the Multicomp Pro and what is not.
All the testers beep if you bump them - sometimes even slightly.
All testers gave false positives on non-energized circuits and surfaces.
Multi-range testers have intermittent response lag in detection.
None of them like really cheap outlets.
The Multicomp Pro Non-Contact Voltage Tester performed better than the other multi-range tester but its real flashlight and IP67 rating makes it a serious contender for space in your tool kit. Understanding what it can and can't do will help you use the tool effectively. If you are going to own a non-contact voltage tester, this one should get serious consideration. It now has a place in my "First in" bag.
Very interesting read, you certainly put it through good real life scenarios. It does have a bit more functionality than the older devices, but I keep looking at some of the Klein NCVT units, but they are so expensive over here.
Good test report.
Very nice roadtest. I really liked your various distance/voltage to threshold/beep tests.
Great review, a totally different approach to mine but pretty much the same conclusions. It’s definitely robust and more responsive and sensitive to a Megger unit I compared it too. I think maybe outlets in the UK are a bit more lightweight than US ones as I could detect a little further away than you. I could also trac cable in the wall, albeit behind plasterboard.
I like the unit.
Nice test plan and review. Relieved to see PPE :-)