Metrel’s MI3000 is the best-selling multi-function tester (MFT) in their range, aimed firmly as a workhorse 17th Edition tester with a few additional useful features. It offers low resistance, continuous resistance and insulation resistance testing, short circuit and fault current testing, RCD, phase rotation and simple voltage testing.
Many electricians are attracted to the MI3000 by its price. Whilst Metrel don’t give it away for free, spec-for-spec it appears to stack up well against the market leaders for a substantial saving. So how does it compare in the real world?
The MI3000 ships with an all-purpose carry bag with a flap for the lead outlet so the meter can be used in situ. There’s space in the bag for test leads and other useful accessories such as lock-off kits and paperwork.
A neck strap for the meter is provided, but the fastenings have an extremely irritating habit of working loose, which in the worst case scenario means your meter goes crashing to the floor. Fortunately the meter itself is relatively robust, and the screen is slightly recessed to limit scratching and damage.
No provision is made for the detachable probes to be contained on the meter or neck strap when not in use, which is a personal bugbear; it’s so easy to drop or lose probes, particularly when working in inaccessible spaces, that I’d like to see some sort of clip or pouch provided, ideally on the strap. At least the crocodile clips can be nipped on to the strap.
Two test leads ship with the MI3000. The first has separate line, earth and neutral leads, each around 1.5m long, terminating in a standard 4mm connector to take a probe or crocodile clip. The probes supplied have somewhat fat ends where insulated, and won’t fit down all but the larger choc block terminals, but the end part of the insulated sleeve is removable, exposing a thin, longer length of conductor (around 30mm) where safe to use.
Use of twisted multistrand cores means the three different cables endlessly tangle in use, so you’ll spend time untangling them each time you take the meter out of the bag, or pick it up after putting it down. Some more thoughtful industrial design wouldn’t go amiss here.
The second test lead terminates in a 3-pin plug, which you might think is useful for testing R1+R2 resistance, insulation resistance and fault currents on circuits with 3-pin socket outlets. However, in practice it’s only useful for fault current and RCD testing, as the meter’s software is preprogrammed to only allow testing between live and neutral leads for all other modes. For example, R1+R2 testing is not practical with this lead as it would only allow R1+Rn testing. This annoying limitation can be fixed by using a breakout plug from another manufacturer, such as Kewtech’s Kewcheck R2, which should be regarded as an essential accessory. Ideally Metrel would ditch their own mostly useless lead and supply something similar.
Both test leads attach to the meter through a proprietary Metrel connector, which means if you damage or lose the leads you have no choice but to go to Metrel for replacements. Neither lead allows remote triggering of the Test button as standard, which is an irritating limitation.
The meter helpfully runs off AA batteries which are rechargeable in situ, so if you get caught short on site with a flat set of batteries, standard alkaline batteries can be used to get you out of
To complete the pack, Metrel provide a charger which is compatible with some of their other meters, plus a manual on CD and calibration certificates. A sliding blanking plate makes it impossible to connect test leads and a charger at the same time, and the meter will not power up when charging.
A rotary dial to the right of the instrument switches quickly between the seven available operating modes, whilst an arrowed keypad on the left allows movement around the screen with an obvious central Test button which is easy enough to find by touch. Calibration gets its own button, as does an occasionally useful Help button which brings up on-screen diagrams which explain connections, if not error symbols (although if you need a diagram to help you connect a resistance meter, you probably shouldn’t be let loose with one in the first place). The final button boosts the screen backlight.
Rapid successive button presses are not registered. For example, if I switch to Insulation Resistance mode, I have to pause before pressing Right to get to the voltage setting, then pause again before pressing Down to change the voltage. Despite this, I get a beep regardless of whether the keypress has been registered. This is hardly a show-stopper, but means if you’re trying to quickly change standard settings repeatedly, you need to be careful you don’t for example apply the wrong test voltage.
The screen is bright and clear, with a good backlight, leading to no issues with reading results. However, some of the pictograms used to flag errors are obscure and unhelpful, which will leave you resorting to the manual. The in-built Help function doesn’t rectify this.
The staple Low Resistance Ohm Meter function is easy to use; simply short circuit the line and neutral test leads, test once to check zero value, hit the Calibrate button if necessary, then attach the leads to the test circuit and hit the Test button for each reading.
The clicking of relays inside the device gives albeit unintentional auditory feedback - a short gap between the clicks means the resistance is low, and a long gap means a higher resistance. This is surprisingly useful when troubleshooting an open circuit in inaccesible circumstances.
The meter supports pass/fail testing, so will award a tick when a result falls under a customisable threshhold, or a cross when it doesn’t. I’d argue this isn’t all that useful, as it encourages operators to trust the machine rather than think about what’s actually happening with the circuit in question, and in any case pass values for resistance testing depend on the individual test and are generally comparative.
The keypad can be used to switch to a Continuity function, which continuously tests resistance once activated, leaving your hands free to control the probes.
I was puzzled to see that if the meter is calibrated to use test leads with high resistance (such as a long trailing lead), if the resistance subsequently drops (for example due to changing to a lower resistance lead), the resistance measurements actually go up, not to zero or a hypothetical negative reading. This makes me question how exactly the meter is calculating circuit resistance and whether it can be relied upon when using a test lead or connection that may have slightly fluctuating resistance.
Insulation Resistance testing is also straightforward. The test voltage can be selected between 100V, 250V, 500V and 1000V, and the meter will test for a couple of seconds before providing a measurement.
Once again, although not by design, you do get a degree of auditory feedback as the voltage generation circuits give out a faint sound which varies by current output; if you’ve accidentally applied a test voltage to a short circuit, you’ll hear your mistake before you see it.
Fault current testing is split between two modes, one of which covers Prospective Short Circuit situations and provides a Z1 measurement (line-neutral), and the other Prospective Fault situations (line-earth) providing a Zs or Ze measurement. This allows the provided 3-pin test lead to be usefully employed in either mode. Both modes require all 3 test leads to be connected, and should an incorrect connection be made, a warning is issued and testing can not take place.
The meter helpfully calculates Prospective Fault Current or Prospective Short Circuit Current values in addition to resistance values, removing the need for further calculation.
Pass/fail functionality is selectable by circuit protection device; for example one can select a BS3036 fuse, rated at 15A with a 0.4s disconnection time and be told whether the Zs value is within tolerance. I’m not sure how many electricians will in practice change the necessary values for each test, and in any case I’d rather spend my time considering what the instrument’s measurements are actually telling me, rather than relying on a yes/no answer.
I bought my instrument prior to the release of the Third Amendment, and at the time of writing (May 2015) there is no available firmware upgrade listed on Metrel’s website to update Zs tables to the new Third Amendment values, rendering the feature somewhat useless anyway.
PFC mode supports low earth current testing (for RCD protected circuits) and normal testing (for example, for determination of Ze at a board). I notice that the measurement varies significantly depending on which method is used, although I’m not clear whether this is a limitation of the instrument or a functional dynamic of the circuits being tested.
As you might expect in the 2010s, RCD testing can be done fully automatically by connecting the three test leads, hitting Test and resetting the RCD manually 4 times. The meter applies current at each phase cycle at IΔn, 5IΔn and ½IΔn and presents all results together, with a tick or a cross for pass or fail depending on the RCD trip current selected.
Trip time can also be measured individually for any current and phase parameter, or ramped testing will increase the current until tripping occurs.
I find that my unit frequently reports an error when RCD testing directly from a board, corresponding to “phase voltage on earth terminal” according to the manual. This triggers a warning beep and testing is not possible. The error seems to depend fairly critically on test lead orientation and good contact at the point of probe connection, but I note that it seldom if ever occurs when testing using a plug-in breakout connector directly onto a circuit outlet. I’m inclined to believe that the unit is oversensitive to a small induced voltage from line to earth circuits across the test leads themselves, although I may be wrong. I appreciate the meter is trying to protect itself and me from electrocution, but its oversensitivity is a practical annoyance.
Voltage measurement works as you’d expect, and is configured for 3-lead use; if you only wish to use 2 leads, you’ll get a voltage reading from the third (floating) lead anyway. No function for DC testing is provided.
Phase Rotation testing means this meter can be used in basic 3-phase situations; if, like me, you only use this occasionally, the on-screen Help menu is useful for confirming which test lead corresponds to which phase.
Crocodile clips have their limitations, particularly the supplied set which don’t positively clamp on to many small or rounded terminals. Therefore you may find yourself trying to hold two (resistance testing) or sometimes 3 (RCD or fault current testing) probes in two hands. The problem arises when you then have to hit the Test button some distance away on the meter - what do you use, your nose?
Metrel do supply an optional probe with a built-in test button, which should be pretty much an essential accessory; unfortunately, it’s bulky, vastly over-engineered, and costs over £100! It really shouldn’t be too much to ask Metrel to supply as standard a line probe with a trigger button. This one limitation is immensely frustrating in use and is the main missing feature which will make me seriously consider other manufacturers when replacing my own unit.
Overall the MI3000 is a decent workhorse 17th Edition test meter, and given its price it’s hard to perceive its limitations too harshly. If you buy it to replace a top-end meter you’ll be mildly disappointed, but as a general everyday use all purpose meter it’s a solid performer.
It would be nice to see Metrel focusing a little bit more design time on niggling issues such as the neck strap buckles and thickness of the probe tips, and thinking a little more carefully about real-world usage such as R1+R2 testing using the supplied 3-pin lead. When I asked Metrel about the latter issue, they got quite stroppy and I wished I hadn’t bothered.
|What's Good||What's Bad|
|Price||Patchy usability issues|
|Solid feature set||Fat probe tips|
|Ease of use||No probe storage|
|Clear screen||Lack of remote Test button for less than a small fortune|
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