PE hands-on product review
EEVBlog
by Julian Edgar
121GW multimeter
An excellent tool available at a good price
I
needed a new multimeter. I’ve used Fluke gear
for years and have two high-quality Fluke multimeters.
And then, for no apparent reason, one of the Fluke
meters simply stopped turning on. But since I’d had that
one for about a decade, I wasn’t hugely put out. But then
the other – a super-expensive, current model Fluke 287 –
developed a fault where it says the leads are in the wrong
sockets. (And when this fault is present – the fault is intermittent – you can’t take a reading!) I browsed the web,
and it turns out it’s actually a common problem with Fluke
meters. Considering how much I paid (about £750) and
how long I’d had it (just a few years) I was very unimpressed. I was even less impressed when Fluke wanted £50
just to look at it – that was before any quote to repair it.
Non-Fluke meter
So, I started looking for a new, non-Fluke meter. And I
looked and I looked. I wanted one with logging, min/max/
average (the ‘averaging’ function is very important to me),
a 50,000 count display and a fast-response bar graph. And
of course, all this with at least decent accuracy.
And then I found a really unusual meter. It started as
a crowdsourced design, but then ended up being made
in South Korea by UEI Test Instruments. It is the work
largely of Dave Jones, who runs EEVblog and who wanted
a meter that had the features he desired. It has on-board
logging to an internal micro-SD card, it has a low-burden
mode when measuring current, it has in-built Bluetooth
and talks to Android and Apple phones (and those phones
can log and speak the measurements). You can even upgrade the firmware via the micro-SD card and perform a
full digital calibration! It’s also been around three or four
years, so it’s not a flash in the pan. And it costs just £160.
EEVBlog 121GW multimeter overview
Let’s take a look at this meter from a strictly practical,
hands-on perspective.
The meter is quite chunky: about 165 x 85 x 55mm (H x
W x D) in its rubberised holster. That said, it easily fits in
Full disclosure
The reviewed meter was bought by the author for
real work at the normal retail price.
66
Fig.1. The EEVBlog 121GW is an unusually well-thought-out
multimeter, with a range of functions including logging to an
on-board micro-SD card, Bluetooth communication with a
phone and in-field upgradeable firmware and calibration. It’s
also well priced!
one hand and can be used with a probe clipped into one
of the rear holders to allow one-hand probing, with the
other hand free for the second probe. Talking of probes,
they’re of silicone construction – the whole meter feels
good quality.
The display is large and easy to read, even in poor light,
and the backlight is excellent – the best I have used in a
multimeter. A smaller secondary display is activated in
some functions (for example, it shows frequency when
Practical Electronics | June | 2023
measuring AC volts) and a fast response, horizontal bar graph is placed
along the bottom of the display.
The meter uses four AA alkaline
cells and one CR1220 button cell –
the latter is for the real-time clock.
Battery life is claimed to be 500 hours.
The meter is largely intuitive to use
– anyone could pick it up and start
making measurements without reading a word of the very clear 73-page
downloadable manual. The rotating
knob selects the usual range of measurements (V, mV, Hz, Ω…) and a
secondary range is accessed by pressing the Mode button. Unfortunately,
the secondary functions are shown
on the meter in red, which is quite
hard to read against the black plastic
background. (The other functions are
shown in white.)
One important feature to know about
is that the meter remembers whatever sub-function you last selected. So,
for example, if you have selected the
continuity function under the Ω selection, the next time you turn on the
meter and select Ω, continuity will be
automatically selected. I find this very
useful, as the meter becomes configured for your most-used functions.
A Low Z mode is available on the
main selection dial. This low impedance mode, used on AC voltages, is
designed to drain ghost voltages.
Other tricky measuring aspects included are that the current-measuring
burden voltage (the voltage drop across
the internal measuring resistor) can
be displayed, continuity can be configured to sound the buzzer when the
circuit is either closed or open, and
diode measurement can be made with
either a 3V or 15V supply. Finally, for
some circuits, power (ie, simultaneous measurement of both current and
voltage) can be directly displayed.
latest logged data file by briefly pressing this button and using the ‘up/down’
arrow keys to scroll back through it.
Unfortunately, pressing the MIN/MAX
key doesn’t show these values from
the logged data. You can also extract
the micro-SD (but removing the meter’s back is required, using a Philip’s
head screwdriver) and read the CSV
file in Excel – for each logged point,
this shows the time (to one second
resolution), the selected meter function and the values. (Note: this logged
data does show the maximum and
minimum values.)
Bluetooth communication
The meter also has a Bluetooth function that allows it to communicate
with your Android or Apple phone
via a free, downloadable App. Having
experienced some problematic multimeter communication approaches
before, I was concerned that setting
up the phone communication would
be difficult – but in fact, it immediately worked.
NEW!
5-year
collection
2017-2021
Handling data
The above features are all well and
good (and no doubt for some people
extremely useful) but for me the two
standouts are the on-board logging and
ability to communicate with a phone.
First, let’s look at logging. The data
logging is activated by pressing the
MEM button until a beep is heard and
a counter starts on the secondary display. This counter shows the number
of samples that have been taken, with
logging able to be configured to occur
at anything from 200ms to 999s (about
17min) intervals. The Auto Power Off
function is disabled during logging.
The logging is of whatever information
is shown on the main and, if activated, the secondary displays.
Logging is halted via the same MEM
button, and then you can review the
Practical Electronics | June | 2023
From your phone you can select different multimeter functions (eg, Range,
Relative and Hold), see a graph of live
or logged data, and configure your
phone to speak the current measurement – either periodically (from 3-60s
intervals) or when a value changes.
This is very cool feature indeed. For
example, you can be monitoring a
voltage (or temperature or frequency
or…) and receive an oral indication
only when the level changes. By using
the Range button, you can even configure the sensitivity of the indication.
Bluetooth range is about 10 metres,
and the meter doesn’t automatically
reconnect when back in range (you
must do this manually).
I’ve not written about accuracy,
because for most people’s applications, repeatability and linearity are
more important than absolute accuracy. However, the meter typically
has a claimed accuracy of better than
±1.5%+10 – the downloadable manual shows the accuracy specs for every
range and function.
Finally, the meter has a bunch of
set-up functions you typically never
see. You can adjust the LCD contrast,
check the meter’s internal battery voltage, give the meter a specific number
ID (useful in companies having multiple meters) and turn the internal
buzzer on and off.
I’m very pleased with the meter…
and I am not going back to Fluke any
time soon!
All 60 issues from Jan 2017
to Dec 2021 for just £44.95
Fig.2. Screen grab from an iPhone
connected to the multimeter via
Bluetooth. In this case the phone was
logging temperature at 200ms intervals
and speaking the temperature every
minute. The main display is using the
supplied thermocouple to measure
temperature, while the secondary display
is showing temperature as sensed by the
meter’s internal sensor.
PDF files ready for
immediate download
See page 6 for further
details and other great
back-issue offers.
Purchase and download at:
www.electronpublishing.com
67
