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Megger MFT1720 Multifunction Tester Details
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Megger MFT1720 Tester Description
The Megger MFT1720 is a all-purpose electrical installation tester for testing, certification and fault finding on both domestic and commercial properties. This model includes tests such as continuity, supply measurement, insulation, Zmax and R1/R2 loop testing, 10mA, 1A and auto RCD testing. An extra leakage current measurement option is also available.
This multifunction tester is designed to work continuously across phases, when connected to a live circuit and even when the incorrect range is selected, making it incredibly reliable.
The MFT1720 features a “Test” button on both ends of the unit for left and right handed users, and a neck strap which enables hands free operation. This tester has also been specifically designed for use in any site whether it is stood up on the floor or balanced on top of ladders the MFT1720 offers high quality testing. With a weight of only 1kg this test equipment is easy to carry and can be carried with you.
The 1700 series is designed to be easy to use and enable an engineer to quickly learn all of the features of this versatile tester. Megger's attention to usability means this tester can be put to use from the day it arrives at your door.
The visual display consists of large, backlit characters, making it incredibly easy to operate quickly regardless of any difficult conditions you may be dealing with. The functionality of this range is increased with up to two parameters can be shown at the same time for easy comparison of results.
The MFT1720 has been manufactured with durability in mind; the sturdy design and rubber moulding mean it can withstand every day wear and tear, as well as long term outdoor use. The IP rating of 54 does little to show the true durability of this tester, since it has been known to survive falls from second story windows and continue to function. With a CAT IV 200V safety rating, the Megger MFT1720 complies with all 17th Edition tester requirements.
This model is now supplied with a carry case as standard, with extra storage room for tools, test leads and certificate pads.
Megger MFT1720 Multifunction Tester Key Features
- System voltage and frequency measurement (TRMS)*
- Insulation test at 100V, 250V, 500V and 1000V (includes input against live circuits up to 600V)
- Continuity resistance at 200mA or 15mA which stars automatically, leaving you free to do other tasks
- Resistance Range up to 100kΩ with customizable fast continuity buzzer
- 2-wire loop test (includes phase-to-phase and non-trip RCD)
- Prospective fault current measurement up to 20kA
- A wide variety of RCD testing capabilites such as Type AC, A, S and programmable RCDs (includes Auto-test routine and 3-Phase RCDs)
- Portable, easy-to-use and extremely sturdy
- Built in strap
Full List of Products Included
- Megger MFT1720 Multifunction Installation Tester
- MFT 1720 user guide
- 3-wire test lead set with croc clips
- SP5 Switched probe
- Mains plug test lead
- Neck strap
- Quick-start guide
- Hard carry-case
- 8 x AA batteries
- Calibration Certificate
- Manufacturers 3 year warranty
- Exclusive £99 City & Guilds Online 17th Edition Course voucher - View Details
Our Expert Electricians' Review of the MFT 1720
The most popular model from the new 1700 series by Megger!
When Megger launched their new 1700 series early last year, their were a few areas of concern with the new models. Some of the 'no trip' settings would still trip RCDs, and there were numerous complaints regarding the use of the same the leads from the 1500 series, which were considered to be the flaw with the 1500 series back in their time.
Megger have responded by updating the firmware of the machines - currently 2.01 - that they distribute and they have updated the firmware of existing machines under their warranty. The leads have also been changed and the general consensus has been positive since their introduction. What follows is a review of the model 1720, which was manufactured by Megger in May this year (firmware 2.01) and so being 'hot off the press' it should be suitable for comparison and review.
The MFT1720 is the middle ground model in the series, and so it has become the most popular. Its features consist of the better options with regards to carrying out inspection and testing of LV installations, whilst it doesn't have additional settings that may be more suited to particular installations - such as 100 V DC insulation test and Earth Electrode resistance measurement.
One of the areas that Megger have been using to promote the new 1700 series is the announcement that it is now a category IV instrument, so what does this mean? Well equipment that is to be utilised with electricity has to be designed for the specific applications and conditions that it can be expected to be applied to.
Different electrical systems result in different tolerances that need to be accommodated on the equipment to maintain accurate measurement. For example, signalling systems will require higher accuracy and be subject to lower voltages, whilst distribution systems will experience higher voltages, spikes and therefore a potentially more dangerous fault condition for the equipment could occur.
So generally, the higher the CAT (category) rating of the equipment, the safer it is - However exceeding or deviating from the required application can lead to inaccurate measurements. Meggers previous series, the 1500 series, was manufactured to CAT III, which referred to the measurement of hard-wired equipment fixed installations, distribution boards, and circuit breakers. Other examples being cables, joint boxes, switches, stationary motors and socket outlets in the fixed installation.
This CAT III has been considered as perfectly acceptable, but by introducing the 1700 series as CAT IV, the instruments are also suitable for measurements referring to the origin or utility level measurements on primary over-current protection devices and on ripple control systems.
Possible over voltages when testing lightning protection systems, inductive loads or photovoltaic systems will benefit from this improved protection.
Test Leads with the MFT 1720
The MFT1720 comes with a complete set of test leads, including a remote probe, new styled tips and croc clips. The leads are very robust and easy to maintain, although you will tend to stab yourself with the tips when you apply them as they are quite firm to insert and are sized perfectly to give you a reminder of how sharp they are by stabbing you in the palm of your hand - the key is to try to twist them on.
The leads themselves have 4mm plugs on the probe, and so only the croc or GS38 compliant tips can be used. This may make continuity testing a little more awkward if you are used to holding the conductors on to the tips with your fingers - once you are used to relying on the crocs more often, this becomes second nature.
The remote probe offers an easy method to carry out insulation resistance tests, and RCD tests - but with the Megger's party piece being the auto test, a remote probe is not essential for other tests.
The crocs have been changed to a noticeably larger scale. Whilst this makes the leverage greater, giving you more control, they may appear a little large and clumsy when using them in consumer units with a quantity of conductors, or smaller enclosures.
This is where we find one of the greatest improvements from the 1500 series to the 1700 series, and from the 1700 series to other new instruments produced today. The MFT1720 screen is large, bold and clear to see at wide angles from the screen. This offers users the more practical option of placing the tester to the side when testing instead of sometimes having to balance it in harms way.
The information given on the screen is well laid out and easy to interpret. The only slight area that seemed a little hard to read was the indication of the phase sequencing, where the conductors L1, L2 & L3 are displayed within the numerals of the voltage being measured. The light for the display is a white light which displays the screen in much more detail compared to the old 1500 series and the Flukes currently produced.
With the Megger's auto-testing feature, nulling the leads requires a simple connection of the two leads connected in the +'ve and -'ve (or L1 and L2) ports to each other and setting the tester to continuity testing (Ω). The tester will automatically carry out the test and gice the value of the leads resistance. Pressing the 'test' button will then zero the display and the zero symbol will be displayed on the screen. As long as the symbol is displayed, then the null is in effect.
Continuity of protective conductors
Continuity testing with a Megger instrument has always been much simpler and quicker than other brand instruments, this is mainly due to the auto testing feature. Keeping the leads connected as with the nulling of the tester, once the MFT1720 is connected across the conductor under test - via either method 1 or method 2 - then the tester will automatically conduct the test.
Continuity of ring final circuits
Step 1 - keeping the instrument nulled from the prior test and using the crocs, simply apply the leads across the conductors and as soon as the second conductor is connected the tester begins the test. With the Megger, this couldn't be simpler.
Step 2 - With previous models the user would have to disconnect the socket outlet accessories, or utilise a socket interface adaptor in order to carry out a continuity test through a socket outlet fascia. But now with these new leads and ports, the same trick that could be done with Flukes can now be done with the 1700 series. Simply grab hold of the mains lead, and connect into the +'ve and -'ve (or L1 and L2) ports just the conductors necessary for the test - In the case of Step 2, Line and Neutral. Step 3 - This is similar to Step 2, however the conductors concerned in the mains lead will be Line and CPC (Earth). With both of these steps and the Megger's auto testing feature, as soon as the lead is entered into the socket outlet it should carry out the continuity measurement. It should also be noted that the mains lead will have to be nulled to maintain accuracy.
To set the instrument for insulation resistance testing simply turn the dial to the required test voltage - this is a much clearer and defined method at selecting applied voltages when compared to Fluke instruments. The leads stay connected to the instrument as with continuity testing. To apply the test there are three options:
- Connect the conductors via crocs and hold the test button
- Connect the conductors via the remote probe and a croc/probe - this allows testing of conductors where crocs can not practically be connected.
- Apply the test and lock it on by pressing the lock button whilst holding the test button - the lock symbol will be displayed for the duration. Then you have both hands free to connect the probes and/or crocs. This method does create the potential danger of accidentally tickling yourself with the applied test voltage (250 V DC - 1000 V DC) and so you need to be sure you are in full control for the duration of this test.
A good feature to the insulation resistance testing is the presence of a live voltage warning. Whenever the tester is set to insulation resistance and is applied to a live circuit, or if the circuit was to be energised whilst under test, then the tester will give an audible warning and switch to displaying the voltage that is present. The will prevent your instrument from becoming damaged.
External earth fault loop impedance (Ze)
To carry out an earth loop impedance test will require a co-ordination of settings between the to selector dials. The first dial is to select between:
- Phase to Earth test mode (3Lp, 2Lo & 2Hi)
- Phase to Neutral (Phase to Phase) test mode (2Hi)
Switching between these two settings will require the leads arrangement to also be adjusted if using a 2 wire testing method. Also when switching between L-E and L-L testing, the applied test current changes automatically to prevent the unwanted tripping of an RCD when applying a L-E test. This becomes evident when you set the tester to L-E and you can see that by pressing the selector button you can change the setting from 3Lo to 2Lo or 2Hi, whilst when set to L-L testing, only the 2Hi option is possible.
It should be observed that applying a 'no-trip' test will be less accurate than applying a more suitable high current test. So the selection of 3Lo or 2Lo testing should only be considered when it cannot be confirmed that an RCD is not included in the circuit under test. So, once it is decided which test current to apply, and which lead configuration to use it is simply a case of applying the leads to the necessary conductors and carrying out the test. On a controlled circuit I carried out a 3Lo and a 2Lo on the same socket outlet to compare the difference in measurement. The variance in value was quite large, measuring 0.18Ω on the 3Lo setting, whilst measured with the 2Lo setting the value was 0.39Ω. It appears that whilst Megger are using the "new 2 lead no-trip testing" as a selling tool for the equipment, it does appear to apply such low test current that the accuracy of the readings is even more off accuracy.
Prospective fault current (PFC)
Like many of the modern multifunction testers on the market today, the 1700 series displays the PFC at the same time as the loop test results - in the upper display. As I state in any review I do, it is important to understand that the measurement of PFC should not be recorded unless the particular requirements for the test are taken into account - in other words, the measurement of Ze requires disconnection of parallel paths whilst PFC requires parallel paths and therefore these tests at the origin of the supply should be carried out separately.
Similar to the Loop and PFC tests, RCD tests require a co-ordination of both dials. The main dial is to be set to the applied rated current - 1/2xI, I and 5xI - or set to Auto, it also can be set to do ramp testing, which is very useful at diagnosing nuisance tripping RCD's. The second dial is to set the rating of the RCD under test - 10mA, 30mA, 100mA, 300mA, 500mA, 1A or VAR for variable RCDs. Pressing the selector button will switch between testing on the 0° and 180° cycles, whilst holding the selector button will allow it to switch between types of RCD. These dials do appear a lot simpler at setting RCD tests when compared to other testers such as the Fluke, which requires a combination of button presses, however someone who is used to the Fluke may consider the RCD dials to be a waste of dial space. Carrying out the RCD test is easy and the display clearly gives the measurement, if the AUTO RCD test is being used then you will need to review the results by pressing the selector button.
One of the new requirements introduced with the 17th edition was phase rotation. The MFT1720 has this feature. Setting the tester to the rotation symbol, and applying the three leads to each of the phase respectively - matching the lead polarity to the apparent polarity.
As mentioned previously, the phase rotation indication can be a little awkward to see on the display as the results are given within the numerals of the voltage indication. One thing worth considering is the way the MFT1720 displays the incorrect rotation. If correct rotation is present it displays this as L1, L2 & L3. But if the rotation is incorrect, regardless of which phases are reversed, it will be displayed as L1,L3 & L2 so it should not be assumed that the incorrect sequence given is a display of the exact sequencing.
This information is given on the Megger website and has been proven with a comparison to a Kewtech KT65 multifunction tester. On an installation with a known phase rotation error between L1 & L3, the phase rotation was accurately recorded as L3, L2 & L1 on the Kewtech, whilst on the MFT1720 it was displayed as L1, L3 & L2.
If a phase rotation problem is discovered then the accurate details of which conductors specifically are reversed can be found by switching the relevant conductors on the instrument, and when phase rotation tests as OK, you can observe your lead configuration to identify the problem.
Other features Max Z - One of the additional loop settings on the secondary dial is 'Max Z'. This is useful for when carrying out a loop test on a ring final circuit or similar circuit where the furthest point utilisation cannot be verified. Simply carry out repeated loop tests and the upper display on the screen will keep record of the highest value of impedance that has been measured. This is a useful feature if you struggle in remembering a simple number.
Zref & R1+R2 - The other two additional loop settings are 'Zref' and 'R1+R2'. This has been introduced to allow the user to take a reference loop measurement,'Zref' - typically the Ze or Zdb - and then if you set the dial to 'R1+R2' and take further loop measurements, the display will deduct the stored 'Zref' from the measured 'Zs' and it will offer a calculated 'R1+R2'. The introduction of this option to calculate the R1+R2 has baffled many electricians, as it is a common understanding that the practice of calculating an R1+R2 from a measured Zs value is not acceptable. Zs measurements are subject to parallel paths and the continuity of a protective conductor cannot be verified, also the resistances of the conductor in reference to their length cannot be determined for comparison. Megger have approached this feature stating you do need to be aware that this isn't a true R1+R2 measurement, it is just an indication because obviously there will be ancillary earth paths
Apparently it is a practical benefit for the user as it helps them to monitor the R1+R2, so it is more of an observational feature? In my opinion it is unnecessary and can encourage bad working practice for new users of the equipment. All this does is deduct one number from another, which surely any individual competent to carry out testing and inspection for a living is more than able to do. It appears to me to be an unnecessary feature that Megger have introduced to add quantity instead of quality features - and the general opinions amongst fellow electricians seems to be very similar.
IClamp - With the additional purchase of the Megger IClamp, the user can carry out earth leakage measurements which is ideal for testing electrodes, leakage on appliances and identifying whether circuits require consideration of high protective conductor currents. This is a useful feature but costs a bit extra.
Carry case One of the common remarks from electricians was there disappointment that megger kept what appeared to be the same case as the 1500 series for the new 1700 series. The older case was often tight for space and was useless when compared to the cases of other tester models, for example Fluke. In fact some electricians have sought to purchase a Fluke case separately to store their Megger in - it appears to be the ideal combination. Megger have claimed that their new 1700 series does come with additional space internally for tools, but as the case is physically the same size as the 1500 series model, all the magic creating extra space has to occur inside. The below image shows a Megger MFT1552 case (to the left) beside the MFT1720 case and the extra space internally does appear evident.
The 1700 series was expected to be a straight replacement for the already market leading 1500 series, but it was not a popular relaunch. Megger have now resolved the majority of the problems and many of the models have been replaced or repaired. Now that Megger have ironed out these problems the 1700 series will become as popular as their predecessors.
Some of the additional features added to the MFT 1720 and 1730 do conflict with what many electricians will consider to be standard practice, and for them they may find the 1710 to be the preferred model. However, with the 1710 having an absence of phase rotation and AUTO RCD testing, it does make the MFT1720 the most suitable middle ground instrument. It is an ideal instrument for any domestic and/or commercial electrician and only those whom have a regular requirement for earth electrode testing or rechargeable/downloadable units should really look to the higher model such as the MFT 1730.
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- Technical Specs
Insulation test ranges:
- 1000 V
- 500 V
- 250 V
- Test Voltage display
- Adjustable buzzer threshold
Continuity and resistance range:
- Easy lead null
- Auto-reverse continuity test
- Adjustable buzzer threshold
Loop Testing Ranges:
- 2 wire no-trip test L-PE
- PFC measurement displayed with loop resistance
- L-PE 48 V to 480 V, 45 Hz to 65 Hz
- High current testing L-L and L-N
- L-L 48 V to 480 V, 45 Hz to 65 Hz
- 20kA fault current
- Zmax value
- R1 + R2 value
- Touch voltage display 0-230 V
RCD Testing Range:
- 1/2 I and SI test
- 0 degrees + 180 degrees phase angle
- Auto RCD testing
- Fast ramp text
- Type AC, A, S RCDs
- Programmable RCDs
- 3 phase RCDs
Voltage Frequency and Phase Rotation Range:
- 6 V - 600V a.c. and d.c. voltage
- Frequency 15 Hz - 400 Hz
- Phase rotation
Intelligent Safety System:
- Immediate test lockout
- Safe contact detector
- Live circuit warnings
- Auto discharge
- Analogue arc display
- Bright, easy-to-read screen with dual display
- Current measurement with an optional clamp
- FREE calibration certificate
- Warranty upgradable to 3 years for free
- Dust and weatherproof to IP54
- Safety rating of CAT IV 300V
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