Fluke 101 Multimeter

Fluke 101 MultimeterImportant: before reading this review, please read this important safety information.

Overview

The Fluke 101 is the cheapest, most basic Fluke available. I say "available", but actually, it isn't officially available worldwide, and if you buy one in the UK, you're technically buying a grey import so don't expect support from Fluke should something go wrong. However, if these are built to Fluke's usual standards, then there's nothing really to worry about - especially at this price.

While earlier models were branded "Fluke" in the usual way, today the brand is printed in Chinese ("福禄克" - paste that into Google Translate and it'll come back with "Fluke"). The manual that came with the meter was printed in Chinese, but an English version is available on the Fluke website.

This meter cost £32.98 delivered, and arrived via tracked post in just 4 days from a UK address. That was a pleasant surprise because the eBay listing said it was coming from Shanghai.

The meter is very basic. For a start, you can't measure current with it. This means there is no need for expensive fuses, and it should make the meter safer as there's no risk of accidents when measuring voltages with the probes in the current sockets (we've all done it!). It's a basic 6000-count meter with average-responding rectification for the AC ranges. As well as AC and DC voltage ranges, there is an AC millivolt function, resistance and continuity, plus capacitance and frequency/duty cycle. But that's it - not even a backlight!

It runs from a pair of AAA batteries, which are included. It is rated to CAT III 600V, and being Fluke, you can believe that. So even if you are on a tight budget, measuring voltages safely can be done!

I suppose there is one nagging concern about this meter at this price - the cheapest I could find anywhere - is it genuine?

Unboxing

The packaging is in Chinese:

Fluke 101 box

Inside we find the probes and manual along with the meter.

Fluke 101 box contents

The probes are the Fluke TL75 types, though the leads don't seem as flexible as some of my older examples. They are rated at CAT III 1000V and CAT IV 600V when used with the protective caps that only leave the last 2-3mm of the probe tip exposed, and CAT II 1000V without. The current rating is 10A, but of course that's academic for this meter. As mentioned, the printed manual is entirely in Chinese, but an English version is available on the Fluke website. There is a certificate of some sort - also in Chinese - and a toxic materials declaration sheet.

The meter itself is made from hard plastic - there's no soft-touch rubbers, plastics or over-moulds here. It feels very solid, as you'd expect.

Operational

There are two buttons on this meter; one for Hold, and the yellow button that changes function in a couple of the modes. Sadly, the Hold button is just a simple type - the same as all the other meters reviewed in this section - so it's pretty pointless. For those who haven't used it, the Fluke "Touch-hold" is really very good, and I recommend it as genuinely useful. But you don't get that on the basic models, naturally.

At the risk of seeming extremely geeky, I've got to say this: the rotary switch is literally the best switch I've ever felt! Really positive and light in action. I sometime pick up the meter just to experience the pleasure of it. But enough of my problems!

Auto-ranging is fast, but the settling time is poor - often giving you several incorrect readings before deciding on the correct answer. Most unlike Fluke, but you get used to it. The continuity test is latching, but doesn't respond as quickly as you'd expect for a Fluke - again, it's OK and you get used to it. My example beeps at <80Ω

The AC bandwith is OK, with -3dB point of 11kHz, which is better than the models we've seen that use the DTM0660 chipset, but not good enough for most audio work. The frequency counter requires about 40mV RMS at 1kHz, and tops out at about 260kHz (it needs about 600mV at this frequency). I was surprised to see that it requires the signal to cross 0V to register, just like many of the cheap models we've looked at here. I tried a couple of other Flukes, and they were fine with a DC offset, though the Brymen BM235 did have the same problem.

In diode test mode, the open-circuit voltage is only 2.5V, so won't light a white/blue LED, and frankly will struggle with others as the test current is only about 600µA.

The display is a little bit smaller than the Aneng AN8002/8 models, but has reasonable contrast and good viewing angles. As mentioned, there is no backlight, which is a shame, as being Fluke, it would have had a sensible timeout rather than the universal 15 seconds that all these cheap meters seem to have.

Unconventionally, the input terminals are on the bottom. As neat as this seems, it is rather awkward with the supplied right-angled probes. I have some Pomona probes with straight plugs (bought for use with my bench multimeters) which work rather better with this meter, and personally, I think that is what Fluke should include by default.

Fluke 101 input terminals

At this point, it's worth comparing the Fluke 101 to the Aneng AN8008. The cases are practically identical apart from the colour! It's surprising that Fluke haven't had words yet!

Fluke 101 compared to the
      Aneng AN8008

The rear panel is fairly plain, with no tilting bail and just a battery cover. The half-turn screw is easily turned using just a fingernail, so changing batteries is a toolless operation. Note the slot at the top for a hanging accessory.

Fluke 101 - rear view

With the cover removed, here are the supplied batteries. Not a brand I recognise! Under one of the batteries is a calibration seal.

Fluke 101

Current consumption varies between 0.9mA and 1.25mA (the AC circuitry increasing consumption by about 0.4mA). With the leads shorted in continuity, the total (including the buzzer) is 16.2mA. When in auto power-down, the consumption is only 6.6µA. The low battery indication comes on at 2.3V, and the meter shuts down at 2.15V, while still continuing to give accurage voltage readings during this time.

Teardown

To open the meter, remove the 4 self-tapping screws and separate the two halves of the case. That's easier said than done because of the deep overlap and tight fit - poking a paper clip in the scew holes and pushing works for me.

Fluke 101 with front panel removed

Note the line in the silk-screen showing where the mode switch should point when the switch is set to "Off". Other than that, there's not much on show here, so we need to remove the PCB. To do that, remove the three small self-tapping screws that secure the display bezel and PCB to the rear of the case (the bezel remains attached to the PCB via a couple of clips). There's no need to disturb the screws on the input sockets:

Fluke 101 - PCB removed

That's better - now we can see lots of the expected Fluke goodness! There a fusible resistor, a couple of MOVs and a PTC, and isolation slots aplenty. Let's take a close look at those, with the PCB placed in the front cover:

Fluke 101 isolation slots
      and blast shields

We can see how the mouldings on the front panel fit into the slots in the PCB to provide blast protection. And look at those input terminals, which are milled from solid material and secured to the PCB with screws and shakeproof washers - this really is a different class to all other budget multimeters discussed in this section. Let's take a closer look at the PCB:

Fluke 101 - input section of PCB

This is the back as you view the meter, so the positive input terminal is on the left. It goes straight into the large 1k fusible resistor (R20) and across to the PTC and MOVs. Meanwhile, there is a string of seven 143k dropper resistors (R2 to R8), adding up to 1M in total. The input imedance of the meter is given as >1MΩ in AC mV, and >10MΩ in AC and DC voltage mode. I would need to reverse-engineer it a bit to work out what is going on, but we will see a large 10M SMT resistor in a moment that might be part of the input divider network.

Note the gold-plated range switch contacts that are generously spaced. On the right is a 10n 1000V EVOX MMK capacitor (C1) feeding the large 1k SMT (R1) resistor and the 10M film resistor (R34).

Finally, the top end of the PCB:

Fluke 101 - processor section
      of PCB

Here we see the main IC is a COB, and next to it is a Microchip 24AA024H 2k EEPROM to store the calibration data. A 4MHz crystal is used. Looking to E1 and E2 - the battery contacts - we see a SMT fuse and inverse polarity protection diode (CR8). Notice the switch contacts (S6) and the four pads WP7, WP8, WP6 and WP9 - these are what are accessible under the calibration sticker in the batter compartment. Next to it is a space for a sticker that is missing in my example, though present in all other teardown photos that I've seen online. Should this worry me???

Note R32, which is a large 10MΩ resistor mounted over a square cutout in the PCB. Presumably that's been done to reduce the risk of tracking, which suggests that this part might be exposed to some high voltages. I also note R25 (1MΩ) that is connected to the same point, but doesn't have any cutouts beneath it. So perhaps that means that the cut-out is to keep leakage to a minimum? More investigation needed.

Conclusions

Assuming this meter has been independently verified like all of Fluke's other multimeters, then this is an obvious meter to pick up for those occasions when you need to safely measure high voltages. As we've seen, it has been built to Fluke's usual standards, using high quality parts and materials. Yes, it's basic in terms of functionality, but other meters - perhaps one or two of the cheap-but-good models reviewed in this section - can be kept for the more advanced or precise low-energy operations on the bench.

Is it genuine? If not, it's a damn good copy! I really see nothing to raise suspicions, apart from perhaps the missing sticker on the PCB. All the components look genuine to me, including the name-brand ones. As it seems to work perfectly on all functions, I'm assuming "innocent until proven guilty" here.

Joe Smith has tested this multimeter and found that it was astonishingly rugged. He hit it with 13kV pulses and it survived and remained completely functional!