Multicomp Pro Non-Contact Voltage Tester - Review

Table of contents

RoadTest: Multicomp Pro Non-Contact Voltage Tester

Author: Andrew J

Creation date:

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?: There are many - take a look on Farnell's website under category Voltage Detectors: There is a cheaper alternative to this one - the MP780052 - which only seems to differ by not having an ATEX certification. During the review, I make comparisons to a Megger VF2 and an Extech EX330 Multimeter with NCV capability

What were the biggest problems encountered?: The device will operate in a low voltage mode by pressing and holding a button marked 12V. I found it quite difficult to keep the device in low voltage mode: I'd have to hold the button down quite firmly and it would often shift in and out of that mode. I found it bad enough that if I had to use it in this mode on low voltages at low frequencies on a day-to-day basis I'd ditch it. For many users this won't be a problem.

Detailed Review:

Thanks to Element 14 and Randall for the opportunity to test this Voltage Detector.


In this review, I have made a number of videos because it can best be demonstrated 'in use'.  Videos aren't my strong point though so I apologise for these in advance and have provided a more textual description of results alongside.


What is a Voltage Detector?

I'd sort of assumed that everyone knew what a voltage detector was, but I was asked this question on a recent forum post so that shows never to make assumptions.  Basically, this is a tool that will indicate the presence of voltage in conductors by beeping, flashing or perhaps both.  It is an essential safety tool for working on electric circuits, particularly for homeowners who change light fightings, plug sockets, switches and so on: you would normally turn off a circuit at the fuse box then use this device to ensure that there are no live wires at the point you are going to work at.  Before doing that though you would use this device on a circuit that is still live to ensure it works correctly.


The Voltage Detector will only detect the presence of AC voltage and will tell you nothing about the level, quality or otherwise of that voltage.  It's purely a presence detector and is dependent on a number of factors for accuracy: insulation type, thickness, grounding, distance to the source and so on.  Therefore a lack of detection does not mean that voltage does not exist and common sense and knowledge of the environment must also be applied.


I mentioned above 'particularly homeowners' only because electricians, in my experience, never seem to turn anything off at the fusebox before working.  However that's not a practice I could recommend and I think every house should have one of these.  It is not an alternative to knowing what you are doing though - in that case, don't go near mains electricity.  I've only been electrocuted twice and it's not something I'd recommend for anyone (once my stupid fault, and once due to the poor regulations in the country I was living in at the time!)


First Impressions

The MP780053 is packaged in a blister pack with instructions and 2 AAA batteries - these are simple devices so there's not a lot to them:



It's actually a re-branded CEM AC-15EX; from the packaging it looks like CEM also make a version that has 'Motor Shaking' capability.  Once unpackaged, it's a fairly funky looking thing:




In the hand, it feels comfortable and is a good size.


I couldn't get a better picture without the parallax error but I can confirm the ruler is aligned with the tips of the detectors.  This shows its size against an alternative I own - a Megger VF2 - and it's a little more compact.  The buttons themselves are a good size even with gloves on and the 12V and Torch buttons have a positive action (there are other issues with the 12V button though which I cover below); the power button less so.  Inserting the batteries is a matter of unscrewing the torch end and dropping them in - polarity is marked on the case so you won't have to dig out instructions when they need changing.  The device is IP67 rated so the end cap must be screwed back on carefully and fully in order to maintain that rating.

Packaging: The blister pack is not recyclable or at least carries no recycling mark which I presume is the same thing.  In this day-and-age, single use plastic should not be used unnecessarily and I think this is a case in point.  The detector will typically sit in a toolbox and needs to be rugged enough to survive that so I see no reason to not use recyclable cardboard packaging.  This is a bit of a bugbear I have and I would urge Farnell to contact its supplier/manufacturer to repackage the item.



Any professional will just unpackage this thing, install the batteries and get on with it.  They aren't difficult to use but I'm interested in how well the instructions are written from a non-technical perspective.  There are detailed warnings about using the product and circumstances where it may not work; usage instructions are clear and written in good English.  Personally, I think these are written in a sufficiently non-technical manner to be clear to a user with no technical or industrial background so to prove that I gave it to such a person and asked them to demonstrate its usage.  That person being my wife and it's one of the tests I cover below.



Rather than list these here, get the up-to-date specs from the datasheet.  The key specification is detection of AC voltages from 12V to 1kV at 50/60Hz.


ATEX Certification

The device is ATEX certified, certificate number: Presale 17 ATEX 9668X. Conformance: EX II 2 G Ex ib op is IIB T4 Gb  (these are the provisions in the legislation that the product conforms to.)  I can't find a way to validate that certificate but they are valid for the lifetime of the product.


ATEX is the formal name given to the two European Directives for controlling explosive atmospheres and is given to devices tested and approved to be intrinsically safe for use in an explosive atmosphere.

  • Directive 1999/92/EC (also known as 'ATEX 153' or the 'ATEX Workplace Directive')
  • Directive 2014/34/EU (also known as 'ATEX 114' or 'the ATEX Equipment Directive')

More information at the HSE website.


The device also carries the CE marking but the two shouldn't be confused.

In the UK, ATEX is being replaced by the UKCA EX scheme and only only UKCA issued EX certificates will be accepted from the 1st January 2022 for products that previously required ATEX Notified Body Certification.  Also in the UK, from January 1st 2021, the UKCA mark replaces the CE mark so products must display this rather than CE; the latter will be accepted until December 31st 2021 subject to certain conditions being met.

Farnell also sell a version of this product that does not carry Atex certification: MP780052MP780052.  This looks to be identical except for the certification so is suitable for anyone not using it in an explosive atmosphere.  And it's cheaper!


IP Protection

An IP rating is a certification, issued by International Electrotechnical Commission (IEC), proving a product meets a certain standard of water and dust proofing/resistance. This device carries an IP67 rating:

  • 6 - resistance to solid ingression which means no “harmful” dust or dirt seeped into the unit after being in direct contact with the matter for up to eight-hours.
  • 7 - water resistance (not water proofing) which means it can be submerged in 1 meter of water for up to 30 minutes.

I'll be testing these claims.


How do Non-Contact Voltage (NCV) Detectors work?

NCVs detect the presence of a live conductor by sensing an electrical field generated by an AC voltage, hence the term non-contact.  Note that they don't detect DC voltages.  Typically, you would test a conductor by holding the tip by the conductor - you probably should test all conductors in case of faulty or incorrect wiring.  Once the tip is placed by a live conductor, the electromagnetic fields induce a current flow through the tester which will light up and/or beep to indicate the presence of voltage.  As indicated earlier, grounding, thickness of insulation, metal conduits or shielding can impact the ability of the detector to perform its job.


There are two ways of doing this detection:

  1. Magnetic induction: the tip has a sensor winding and when this is placed in the generated electromagnetic field a voltage is induced and used to trigger the alarm.  This requires a complete circuit with current flowing for the detector to work.
  2. Capacitive coupling: a capacitively coupled series circuit is created between (a) the conductor and tip of the detector as a small capacitor; and (b) the user and ground as a large capacitor.  The user and ground form a larger capacitor than the conductor and tip and that allows a greater voltage to develop in the sensing circuit to trigger the alarm.  It doesn't require a complete circuit to work but the user can't be fully isolated nor can they be at the same potential as the voltage in the conductor.


Here you can see the sensor in the tip of the detector.  This detector is of the capacitive coupling type, and I believe most are: although not specifically described as such a device, the instructions state "Lack of indication occurs if.....fully isolated users prevent an effective ground"; I can get it to beep and light just by tapping it onto my grounded ESD mat; and I can place it near a conductor where it will alarm if I move my hand over it even without touching.  As I understand it, with capacitive coupled devices, sensitivity to voltage is linked to its frequency: so it is sensitive to high voltages at low frequencies and low voltages at high frequencies.  Some of my testing below bears this out.


The MP780053 in Operation

As mentioned previously, these types of devices are simple to use: turn it on, point it at a live conductor and see/hear it alarm.  This device has both a light indication and a sound indication.  Functionality:

  • Tip lights green when it's turned on
  • Tip turns red and a beeper sounds when voltage within the set range is detected: normal mode100V to 1kV; low voltage mode: 12V to 1kV.  Beeping gets progressively faster the closer the tip is placed to the live conductor when in the low voltage mode.
  • The beeper can be turned off.
  • The tip has a built in bulb that lights the area being pointed at
  • The rear has a much brighter torch to give wider illumination for use in dark spaces


I've created the video to show a simple overview of operation:




The following tests are to further demonstrate features of the device and, where it makes sense, to compare against two other NCV detectors I own.

Extech EX330


Image from the official Extech EX330 website. This works by pressing the NCV button and watching the red led at the top light up - it makes a pretty weedy warble as well.  Works well enough though.


Megger VF2


Image from the official Megger VF2 website.  Fewer features than the Multicomp Pro device but works the same way: tip lights and a beeper sounds when detection is made.


Non-Technical User Test

For non-professionals, I'm interested in how clear the instructions are both in terms of the detector's usage but also in the warnings given.  So I gave it to my wife, along with the instructions, sent her away and asked her to come back when she could demo it.  Within a couple of minutes I could hear beeping emanating from other rooms in the house and within five minutes she'd returned back to me.  So, very quickly she could read and understand these and successfully demonstrate it working, demonstrate it tracing the path of a live wire up the inside of a wall from a light switch and explain about proximity to the live conductor.  She wasn't too bad on the warnings or why it may not work after a little prompting from me - "it's a lot to remember".  She would not understand any reference to "effective ground".


I'd certainly conclude that the instructions are clear enough for any householder to make proper use of it after reading, and that was what I was mainly interested in.  In my view, the main warning to "test the device against a known live source" should be more up-front and centre in bold: if there's one warning that should be clear it's that one.  All the safety information is in one section, clearly marked, but there is no differentiation of font and there are 12 bullet points in total - that main one being number 4 -  including less relevant points such as "remove the batteries if not to be used for a long time" and " Turn it off when not in use to save the battery"


I wouldn't mark it down on this mainly because nobody should be messing with mains electricity if they don't know what they are doing, irrespective of access to such a device or accessibility of instructions.


Care with Using/Testing

Care needs to be taken when using NCV detectors and an awareness of environment is important.  They need to be used very specifically and deliberately and, even so, one might want to double check with some alternate source.  Depending upon their sensitivity, they can pick up stray radiation and falsely trigger.  Here's a couple of videos that shows the problem, and how some devices can be worse than others - I'm pretty sure I don't have 100V+ floating around in the air:



I can't honestly say I understand fully what is happening or why orientation of the device matters, but it's clear that taking readings can be upset by devices emitting radiation in the general area.  The Multicomp Pro device is a lot more sensitive than the Megger VF2 and about the same as the Extech EX330.


Depth and Proximity

A NCV detector is proximity based - it has to be 'close' to a live conductor to detect it.  You'd hope that pointing at a light switch or a plug socket would be good enough to detect a voltage, but is that so?  What about a buried cable in a wall?  How close to a conductor does this device need to be to detect a voltage?


As noted in the instructions, and to be expected really, it depends upon any shielding of conductors.  Anything in a metal conduit is unlikely to be detected but using the device to look for a buried cable that alarms at least gives you notice something is there; conversely, looking for a buried cable in the wall that doesn't alarm tells you nothing and the result shouldn't be trusted.


These two videos show this in practice.  Firstly, a proximity test: the further away from a conductor the detection occurs, the safer using the device is likely to be.


Secondly, a hidden conductor test.


The videos show that the Multicomp Pro detector is more sensitive than the Megger VF2, and slightly less so than the Extech EX330 - it detected the live conductor from 2cm - 3cm distance.  It could also detect a buried, live conductor from around 5mm away from an 18mm (?) plasterboard wall which is pretty good I think - the Megger couldn't detect it at all.


In low voltage mode down at 12Vac and 50Hz/60Hz, the Multicomp Pro has to be very close to the conductor, practically touching it, for detection to work.  See the test below for a demonstration.


Low Light Working

The detector has a built in torch at one end as well as a light at the business end.  I can't say I'd rely on these lights when trying to detect voltage in a dark room - surely you'd have a working light - but let's see how well they work in practice.  My loft (attic) is nice and dark when the hatch is shut.


The video shows me testing the torches for the Multicomp Pro device and the Megger VF2 (the Extech has no torch so there's no point in comparing that.)  Results:

  • The Multicomp Pro detector's front light is excellent in a dark environment.  It's not a torch in the conventional sense but it's powerful enough to light up a small area around the working point and see that you are actually pointing the device in the right places.
  • Both the Multicomp Pro and Megger have reasonable torches built-in with the Multicomp Pro's being slightly better.  Neither would be better than a proper working light to be honest but in a pinch, better than nothing.
  • The Megger doesn't have a business end light like the Multicomp Pro.  Even with it's torch turned on, it's pointing in the opposite direction to where you need to work so is useless in that sense.  The tip itself only lights when it detects voltage so in the dark you have very little idea of where it is pointing.
  • The sensitivity of the Multicomp Pro device really shone through.  Having turned off the loft light, it would still detect a voltage in the light switch box and the cable running to it.  The Megger detected nothing at all even though the conductor isn't buried and is live.


In the video, the torch turning off with a few beeps is an indication that the batteries are too low voltage to work the torch.  The detector unit has its own, separate low voltage detection and continues to work ok.  The batteries were the ones that arrived with the unit and have only been subjected to less than 1 hour of actual use which isn't great.  For comparison, I've had the Megger VF2 for years - I can't remember how long - and I've never changed its batteries.  It easily has enough accumulated hours of use to match the Multicomp Pro.  I've found this in the past with devices that come with batteries so I can only recommend that fresh ones are installed from the start.


I'm impressed with the front working-area light as it works very well coupled with the tip that is lit green.  I'm also impressed with the sensitivity compared with the Megger VF2: the latter could well falsely indicate the lack of voltage when in fact the insulation is just too thick or the conductors are mounted in surface boxes too far from the front face of the box.


Low Voltage Detection

The overall range of the detector is stated at 12V to 1kV.  I can't test that high, but I should be able to test around its low point.  My idea is to set my AWG to generate a 50Hz, 12Vp-p sine wave to test if the detector will pick it up in low voltage mode.  The instructions tell me that when I press the 12V button to put it into low voltage mode:

The tip will turn yellow and whilst keeping the 12V button pressed, place near an AC voltage.  When AC voltage is detected, the yellow led will turn off, the red led will flash and the sounder will beep.  The flashing and beeping rate will increase the closer to the source of the voltage the tip gets.  If it tests a high voltage, it will automatically switch over to high voltage mode, the red led will be solid and the beeper will sound.  Note that the red led will only flash, and the beeping rate will only change, when low voltage is detected.

What I found in practice is that it was difficult to get it to stay in 12V mode.  When I pressed and held the button, and I had to do so quite hard, the tip would turn yellow but then would turn back green or alternate between the two.  It would occasionally beep and turn red then back to green.  Sometimes it stayed yellow.  Overall, I found it awkward to use in this mode and I wouldn't want to be using it on a day-to-day basis.


My frequency generator actually needed to put out a 20Vpk-pk sine wave to deliver 10Vdc, or 7Vac rms  (10 * 0.7).  Therefore, I built a small Op-Amp circuit to double this up to a nominal 14Vac although in practice it hit the rails at 12.5Vac but was still good enough:



(with thanks to Donald Lane () and Ralph Yamamoto () who helped me resolve a problem I was having with it)

By reducing the Vp-p on my generator from 20V I could steadily reduce the actual output voltage below 12Vac


I did manage to get it working long enough to get some results, but my thumb was quite sore by the end!  The video below shows this and I apologise for the quality but I had to keep my eye on the tip of the detector to make sure it stayed in 12V mode and my hand became a little shaky because of the pressure I needed to use to keep the button pressed.  If you'd rather not watch it, what I found:

  • The device will detect 12Vac but it has to be held very close and carefully to the conductor.  It has no rapid beeping or flashing 'the closer it gets' because it is practically touching to detect anything.  It took a lot of positioning to get a detection so you would need to take your time and, ultimately, if it didn't detect I'm not convinced that you could be sure the conductor wasn't live.
  • It will detect voltages as low as 10Vac.  Below this voltage level, it was impossible to determine if it was detecting a real voltage or just flagging a false positive.



In reality, detecting such low voltages is likely to be a specialised use of the device against a circuit that isn't so Heath-Robinson.  I also expect nobody will have to stand holding the 12V button for extended periods of time.  Given the difficulty I had I'm afraid I wouldn't trust the device to tell me if a conductor was live at such a low voltage and slow frequency - see test below.  Nonetheless, detecting down to 10Vac is pretty good and they've left headroom in the spec; it may be that other units are less difficult to use.


Frequency Detection

The device is rated to detect at 50Hz/60Hz and I was interested in how far from these frequencies it would work.  The only way I can do this is by using my frequency generator with the device in low voltage mode; I was going to create a video to show the results but given the issues I had with the low voltage detection test I decided against it: my practice attempts were just too difficult and the videos unusable.  Using the same circuit, with the output set at 12.5Vac, I steadily altered the frequency output of the sine wave.  The results:

  • 50Hz - 60Hz: detection is ok, and actually better at 60Hz rather than 50Hz.  The device only reports with a slow rate of beeping and flashing of the tip.  In theory, it should beep/flash faster the closer to the voltage source it gets but this wasn't the case at this voltage/frequency because I found detection only possible when extremely close to the conductor.
  • 45Hz: detection became erratic and it was unclear whether it was detecting anything or just reporting false positives.
  • 100Hz - 10kHz: worked well, and I could hold the detector further away from the conductor to trigger.  It would beep/flash more quickly as I brought it closer to the conductor.  At 5kHz, the generator output voltage had dropped to 11.5Vac and at 10kHz to 8.4Vac.  It would seem that there is a relationship between frequency and voltage for successful detection as the low voltage detection test was very unclear at 8.5Vac 50Hz.
  • 20kHz: stopped detecting as well so it was unclear if it was reading false positives.  However, in fairness to the device, the output voltage it was attempting to detect was only 4.3Vac at this frequency.


I'd have thought before doing this that the device would have quite a narrow frequency range but it seems that it's good up to at least 10kHz at low voltage.  It also works better the higher the frequency and can detect lower voltages at higher frequencies very well!  As I mentioned earlier, voltage and frequency are linked when it comes to detection and this testing bears this out.  I can't test frequencies at higher voltages as I only have access to mains AC and I'm not prepared to mess with that but my assumption would be that it works just as well.


Ingress Protection Tests

There's a good article on how these tests are officially undertaken on F2 Lab's website.  Assuming it survives these tests, I will only open the battery compartment to test for success rather than pry the unit apart - there are no visible screws or other clips so such an act would be destructive.  To pass any of these tests, the device must:

  • show no indication of liquid/solid ingress
  • detect a  240Vac/50Hz voltage in a light switch and buried conductor (as in the demonstration earlier in the test)
  • still have a working torch
  • still have a working front light


Dust Ingression Test

The device is rated at IP6x:

This rating applies to hazardous parts that can’t be accessed, even with a wire, and protection against ingress from dust is also applicable. This is tested using a 1.0 mm access probe and by inspection to ensure that no dust or particles enter the device.


It's rated for up to 8 hours against solid ingression.  The official test would use a vacuum barb installed in the device to try and pull in dust or particles but I can't go that far.  In my experience, the best way to test dust resistance would be to put it in my pocket, climb on a camel and take a ride in the Sahara.  That dust will get through three layers of clothing as well as a camera bag and into a camera mechanism.  The next best thing would be a dusty environment such as a flour mill or paper mill but that's not an avenue open to me either.   Instead, I will do two tests.


Bury Test

I buried the device under sand for 4 hours, then extracted, brushed the sand off and tested.


It was completely covered in this sand/ash mix.


Very dusty when it was extracted and you can see particles within the moulding of the rubber grips.  I cleaned this off as well as I could.


The device worked perfectly well and passed all the tests.  No dust or particles had passed the seal for the battery compartment.


"Wind" Test

I placed the device in a bag with some of the same sand, then gently shook and manipulated for 5 minutes to mix things up - an attempt to simulate dust and particles being blown around in a draughty or windy environment.  Brushed the sand off and tested.


Apart from being very dusty, it passed all tests again.  No dust or particles had passed the seal for the battery compartment.


Water Resistance Test

The device is rated at IPx7:

IPX6: This rating is given for items that can provide protection against ingress from powerful jets of liquid. It’s an extended version of IPX5. The water pressure in this test can reach 14.5 pounds per square inch (PSI).
IPX7: This rating goes further and indicates protection from temporary immersion in liquids. The rating is given after immersing an item in 1 meter of water for 30 minutes with no harmful effects.

I've given both IPx6 and IPx7 as IP ratings build on each other.  Pressure of liquid application is important in this type of protection and 'jetting' water is likely to be more problematic than immersion in still water.  For this testing, I will undertake three tests.


Quick Immersion Test

Drop the device into 8cm of water in a bowl, quickly extracted and patted dry.


Passed all tests perfectly with no water penetration past the battery compartment seal and none visible in the tip.  As a bonus it cleaned a lot of the dust off it as well.


Rain Test

This is to simulate the usage outside in rainy conditions.  The standard calls for 'powerful jets' at IPx6 and yet only 14PSI.  My jet wash is 90bar which is 1305PSI so a bit too strong! 14PSI isn't even 1 atmosphere of pressure so I shall turn the device on, place on the ground and then run a very gentle spray from a hose over it for 30 seconds then dry it off.  I'd consider it unfair to direct even hose pressure jets when I can't measure the pressure.


Passed all tests perfectly.  No sign of water in the tip or penetration beyond the battery compartment seal.


Long Immersion Test

It should last 30 minutes when submerged to 1m in water.  I'm going to place this in my pond to a depth of 80 cm for 20 minutes, fish it out and pat it dry.


Tip down with some wire attached for easy retrieval.  The pond is 80cm deep at this point and the tip is just above the silt you can see.


After fishing it out and patting it dry, it works perfectly.  There is no water in the tip and no penetration past the battery compartment seal.  It's nice and clean again too.


Drop Test

The specifications say it can survive a drop of 2m onto a hard surface.  By coincidence, my light fittings are 2m from the floor so I dropped it from that height onto hard wood - I wasn't trying to be specific in how it fell so, for example, I didn't purposefully drop it onto the tip.  I tested the device after the drop:

  • nothing should be broken and it shouldn't rattle or make any other unusual noise
  • detect a  240Vac/50Hz voltage in a light switch and buried conductor (as in the demonstration earlier in the test)
  • still have a working torch
  • still have a working front light

and indeed it worked perfectly.


Summary and Conclusion

The Multicomp Pro MP780053 is a really good voltage tester.  The front light and led-lit tip are excellent for working in low light conditions; its sensitivity is good for detecting voltages where the Megger VF2 failed to do so.  It does work down to 12Vac at 50Hz/60Hz but I'd have to presume that it works up to 1kVac as I'm not able to test it beyond 240Vac.  It's rugged as well and should be very capable of living life rattling around in a toolbox and working in dusty/wet environments.


I found the 12V detection difficult and careful positioning and patience is required.  This wasn't helped by the 12V button being hard to engage and intermittent in working.  As such, I wouldn't trust a negative voltage result at such a low voltage and frequency.  The button issue may just be the unit I had of course: I've asked the other reviewer if he can comment on this.  The sensitivity was great for detection but also had a downside in that it would readily pick up environmental radiation; this could lead to false positives and anyone using the device should be fully aware of where they are working.


Not all the scoring categories are appropriate for this device and I've left them at 10 so as not to look like it's being penalised.  The specifications and instructions are very good but I'd like to see the important warnings separated from the general safety instructions.  Given it's ruggedness, I'd also like the blister pack to be rethought.  The score I gave it reflected the issues I had with the low voltage detection and not the packaging.


I would recommend this device to anyone who has to work in a potentially explosive environment at higher than 12V.  If 12V is your thing, then I'd want to try a couple out first before investing heavily in volume units.  For anyone who doesn't need to work in an explosive environment, and for householders, the Multicomp Pro MP780052Multicomp Pro MP780052 seems to offer exactly the same features but without the ATEX certification and nearly half the price (in the UK.)  It's competitively priced against other similar units on Farnell's website; I'd definitely recommend this unit over the Megger VF2.  If I ever had to buy a NCV in the future, it would definitely have the lit tip and front-facing light.


It would seem Farnell will need to deal with the ATEX certification and CE marking within the next 12 months.


I'm happy to answer any questions or run further tests that I'm able to.  Just leave me a comment below.

  • Finally got around to reading this. Very nice review and thoroughly tested.


    I did end up getting one myself, but have been unable to verify the ATEX certificate, so it just sits around on the bench at the moment. I cannot use it in a hazardous area without the certification, as that gives the limitations on the use of the device.


    The buttons are tough little blighters on my unit too but I have also found that to be the case on the Whia unit I have as well.

  • Thanks Mike, I think we did very complementary reviews.  I’m rubbish at videos but it felt like this one called out for demonstration.  Except when my arm was falling off during the low voltage tests image


    I still wonder why orientation of the unit mattered when picking up false responses - the sensor was still within the fields and facing towards the objects generating them.  And of course we talk about false responses but it’s clearly detecting the radiation in the air so it can’t really be false.  Perhaps unhelpful responses would be better!


    I couldn’t replicate your Christmas lights testing as mine were too low voltage at low frequency to reliably detect and my thumb was begging for mercy.  Or it just gave unhelpful responses as I got to within a foot of the string.


    Overall I’m impressed with it though, and the non-ex version is a bargain compared to other units on the market.

  • I think the greater sensitivity of the Multicomp Pro unit enables it to detect voltages better - demo’d by the comparison against the light switch and cable tracing.  On the other hand its greater sensitivity enabled to pick up “false” indications easier - demo’d when I was waving it around on my desktop. 


    For anyone who hasn’t used these types of devices before I’d feel a need to add a warning: lack of detection does not mean a lack of energised cable.  You would still need to be careful about drilling into walls anywhere near a socket or switch notwithstanding building regs that say where cable should be routed.


    Conversely, detection doesn’t necessarily mean an energised cable as it may just be picking up stray fields.  I suppose that at least fails safe!

  •   Great review.  Good choice to go with the videos.  There just aren't enough words to describe some of what we saw.  I also couldn't tell if it was my finger slipping off the button or the tester reverting back into high voltage mode.  It certainly hurt after after doing a bunch of low voltage tests.  You went all out on the IP67 testing.  Very impressive.


    I was amused that we both took videos of the false responses.  With us only having 120v here in the US, I could get the tester to figure out which side of the cord had the hot and which side had the neutral and/or ground.  That is, unless it was a false positive.  I still have yet to put a scope on the ground - because what do I reference it to?


    Again, great review.

  • Great review Andrew.  (not sure how I missed this when it first came out).  I found myself being quite confused as to if it was too sensitive or not.  I like that you compared it to other devices, but again, not sure if one is better than the other given that they could trigger off other signals and not necessarily the signal of interest.  I guess the assumption here is it better to be safe than sorry.


    Well done.

  • Microcap is Spice under the covers, it just has a way nicer interface from what I can tell.  I've downloaded it but haven't played with it yet.  Seems to have a fair few models and circuits built in.  I'm speaking from the point of view of course of someone who has been using LTSpice on MacOS! 

  • Microcap? No. What does it give me over Tina-TI and LTSpice? I downloaded the Microchip one some time back and installed it, but haven't used it for anything yet, so I've currently got a backlog of simulators to try, but I could give it a go.


    I don't know how they actually do it circuit-wise. As you say, given the numbers involved it might just be a single, application-specific chip. Perhaps wait and see if Mike takes his apart before destroying yours.


    Try and imagine the electric field in space resulting from all the wires at mains voltage and the various walls and surfaces at something like ground potential. It's going to be quite complex. Now you introduce your arm and hand (something like, but not quite, an extension of ground) and then wave them around. As science experiments go, it's probably not the most precise way to map out a field.


    Fun electric field fact: outside, there's about 100V for each metre height above the ground (due to the high charge up on the ionosphere). Apparently. If my memory serves me correctly. I should think it's quite difficult to measure, though - think about how you'd do it and you'll quickly run into the problem of how to stop the measurement from affecting the result in a massive way.

  • I guess you know Microcap is available free now right? 


    They definitely work using a capacitive divider approach with a small capacitor at the tip (conductor:AIR:tip) and the user (body:SHOES,CARPET,WHATEVER: ground)  Given there is a potential difference generated, so is a current and I suspect they use something like BJTs to amplify and drive a buzzer/light.  Given that it tends to signal positively rather than a bit wishy-washy depending on the voltage potential, they may use a schmitt trigger or something. I wouldn't be surprised if there is an IC that can do all this.  I don't know, just a guess, could just as easily be an opamp I suppose.  I could take it apart for the right fee image!  That's really destructive though and I quite like it.


    I don't understand why you object to a voltage in mid-air. Isn't that what we mean by an electric field?


    I never thought about it in that way but yes it is.  I was more surprised by the detection in 100V mode and confused by orientation affecting the detection but perhaps explained by all the conductors being laid flat??

  • Hello Andrew. Good review.


    I couldn't resist trying it in a simulator (you know what I'm like with these kind of things).


    I think this is probably a crude, simplified model of what you've got there. I plucked the values out

    of the aether, so it won't be accurate at all, but hopefully they're in the right sort of area so

    that it gives an idea of what's going on.





    Effectively, it's a capacitive divider with load resistors betweeen the capacitors. It looks like it

    gives plenty of voltage to detect.


    The value for the input resistance of the op amp was just a stab at a likely value. I can't push it

    any higher than the 1G because, if I do, the simulator then objects to it being an 'irregular

    circuit' as it can't do the dc analysis.


    The 5pF I've got for the probe-0V-to-hand capacitance might well be a good bit higher: the complete

    metal outer of one of the batteries might be the circuit reference and would couple well with a hand

    wrapped around the probe, alternatively there could be a metal sleeve within.


    One thing that's not right with it, as a model, is that I've got the body of the operator purely as a

    resistor and then a capacitance to earth. In reality there's also some capacitance to mains wiring as

    well, so the hand will have some ac voltage on it, somewhere between mains and ground, which will

    then desensitize the probe a bit.


    If you wanted to make it a bit more sensitive on 12V, one way might be to add an additional piece of

    metal in front of, but close to, the tip active area. I think that would work: even though you would

    be dividing it into effectively two capacitors in series, the metal-to-circuit-wire part would be

    higher because of the larger area and the metal-to-probe-tip section would be higher because of the

    shorter distance, so even together in series they'd still exceed what you had before. Take it too far

    though and it will just be swamped by mains, given how pervasive mains electric fields are indoors.


    I don't understand why you object to a voltage in mid-air. Isn't that what we mean by an electric

    field? I know that the physics is a little outdated now, but electric and magnetic fields still work

    reasonably well as engineering models.

  • Thanks Gary.  Despite the issue with the 12V button, it’s a good device.