Table of Contents
Introduction
I was on the lookout for a decent multimeter, but didn’t want to spend a lot! By chance, I saw the MP730624 multimeter - a meter with 4.5 digits, 20,000 counts, Bluetooth, and a surprisingly good specification. I had to try it out! Fortunately, it was relatively affordable too (£48 including tax in the UK, or 60 USD), which is always nice. I think it’s the perfect multimeter for home use, and for classrooms (the Bluetooth logging capability lets you view and log your experiment measurements with a lot of accuracy! on Chromebooks, phones, and PCs).
I liked it enough to want to create an app for it. See the 3-minute video below. The meter does already come with Android and iPhone apps, with charting capability too, but I didn’t try them (this is a very short review! If you try the apps, please share some feedback and screenshots). My app is cross-platform, for desktop and mobile use; it is a web-enabled app and can be run in a browser, or installed on the machine.
Special thanks to Jan Cumps for spot-checking some of the information in this blog post, and to baldengineer for the initial BLE decoding work on a similar meter, which proved to be similar to what was required for this meter too.
What comes in the Box?
The meter is supplied with probes, a 9V battery, a little screwdriver, and a thermocouple. The probes are OK, but I replaced them with slightly better probes . The new probes are very sharp and come with a variety of tips in different sizes. I liked the tips shown in the photo, they were successful at accidentally drawing blood.
The meter is supplied with a very decent user guide also available as a PDF, as well as a technical spec sheet. The supplied documents have large text, useful images, and thick paper - all good quality.
Using the Meter
The display is very clear, and the backlight is good too. It is way more readable than the Fluke 87V.
I also liked that the range is displayed (there is a little digit 2 underneath the decimal point in the photo). However, the text there is tiny – I wish it were more prominent.
The meter is highly accurate – way more than a typical meter! More on that further below.
Using the meter feels fine – this is my second Multicomp meter, and I’m generally happy with the usability. It is simple to use. There are no complicated button sequences. The dial is a bit busy, though – perhaps if they had left out the non-contact voltage (NCV) detector feature, that could have been one less indent on the dial.
I also liked that the meter will not auto-power off if Bluetooth is being used, so it can be used for (almost) endless logging.
Things I didn’t like
To get the negative points out of the way first: I didn’t like that there was no Min/Max capability, and the AC bandwidth is unspectacular (it is 1 kHz), and, the resistance and continuity tests are slow. In the resistance mode, it takes about a second to approach a stable value, when auto-ranging is deselected (it is, of course, expected to be slower with auto-ranging turned on). The continuity check has some lag, perhaps 50-100msec; it won’t register continuity if the contact is made for very short periods of this order.
Other than that, there’s not much wrong with the product. I spotted one or two minor idiosyncrasies, but nothing significant.
Things I liked
First off, the meter is highly accurate, and the measurements are granular. For the most part, the accuracy is in the same league as Fluke 87V and 121GW multimeters. I did a few spot checks, and my multimeter is operating to specification. Whether it will remain accurate in a year's time, I cannot say. As supplied, it is certainly functioning well.
As mentioned, the display is excellent, and it’s good to see that the range is explicitly indicated, rather than requiring the user to infer it.
I also liked the Bluetooth (BLE) capability; it is fast, with no significant lag between the multimeter readings on the device and on the PC/mobile.
Two of the most important measurement types, voltage, and current, are fast; the update rate is about 3 Hz, so it feels speedy.
The meter has a built-in 20 MHz frequency counter (I tested it up to 10 MHz for now), and it can measure duty cycle to 0.1 percent granularity.
The capacitance measurement capability is excellent; very granular (down to 0.1 pF).
Measurement Accuracy
The chart below shows how the meter specification compares with the Fluke 87V and 121GW meters. I merely chose to compare against these meters in case others had these so that it is easy to get an idea of the performance. Note: I cannot guarantee there are no mistakes in the chart, so for critical measurements, please don’t rely on it without checking for yourself, and please comment if you identify any errors.
The chart is used in the following way: the x-axis indicates the desired voltage to be measured, from 1 uV to 1kV (the chart is logarithmic), and then you can read off on the y-axis the worst-case error that the meter will display. The lower, the better, of course. The X markers indicate some spot checks performed with the Multicomp and Fluke and 121GW meters (thanks Jan).
To understand the chart, let's look at the colored lines:
It can be seen that for very low voltage measurement, up to around 20 mV on the X-axis, the green line is the lowest, and the Multicomp meter has excellent performance. Beyond that, the Multicomp meter is overall more accurate than the Fluke 87V in its hi-res mode, which is the yellow line (the Fluke 87V has a 6000-count normal mode, and a 20,000-count hi-res mode).
Looking at the blue line, you can see that the 121GW is mostly more accurate across all the ranges beyond 20 mV.
But, looking at the bigger picture, to put things in context, although this chart reveals the differences, all three meters are very accurate. This is all extremely good performance for handheld devices, and way more accurate than is usually required.
Next, the DC current measurement accuracy specification was examined:
At the low current ranges, up to about 100uA, the Multicomp meter has a better specification than the Fluke 87V. Beyond that, the performance is about the same on balance, but only up to 200 mA. This is because the Multicomp meter is missing a 2A range. You have to use a 20A range for any measurements beyond 200 mA.
The 121GW meter is especially excellent for low tens of uA measurements. However, all-in-all, across all ranges in general, the 121GW performs very well.
Again, all three meters have excellent performance, with each one winning out for certain parts of specific ranges. For the very lowest current measurements, you’ll want to use the Multicomp or (even better) the 121 GW.
I didn’t chart the other measurement types that the meter supports (it takes some time to prepare the charts, it is not a fully automated task, and this was supposed to be a quick review!). However, the PDF specification makes for some pleasant reading, the meter has fairly good accuracy across the board.
Using Bluetooth
As mentioned earlier, there are pre-existing Android and iOS apps that could be used. I didn’t try them. My app source code is on Github and to use it, click here --> BLE Multimeter App (regardless of desktop or mobile platform, the same link should work, because it is a web app). If you’re using an Apple iOS device, then an app called WEBBLE needs to be installed from the Apple Store first however, because the default browser in iPhones and iPads does not support Bluetooth.
If you’re working in an area without Internet access, the app can be installed to the device, or can be downloaded and used offline.
In future, it would be great to extend the app to provide charting capability and CSV format output. Today it dumps the measurements (and timestamps) to the display, with a header followed by a CSV-compatible format (press Ctrl-A and Ctrl-C to capture it).
Here is some example output to see the format:
MP730624 Digital Multimeter 1 0.0000 V DCV 2 V Data Log Auto-scroll Requesting any Bluetooth Device... Connecting to GATT Server... Getting Primary Service... Getting SendReq Characteristic... Add Event Handler for Notifications... Start Notifications... Ready. 01:52:56, DCV [2 V], 0.0001 V 01:52:56, DCV [2 V], 0.0001 V 01:52:57, DCV [2 V], 0.0001 V 01:52:58, DCV [2 V], 0.0001 V 01:52:58, DCV [2 V], 0.0001 V 01:52:59, DCV [2 V], 0.0001 V 01:52:59, DCV [2 V], 0.0000 V 01:52:59, DCV [2 V], 0.0000 V 01:53:00, DCV [2 V], 0.0000 V 01:53:01, DCV [2 V], 0.0001 V 01:53:01, DCV [2 V], 0.0001 V
Summary
The MP730624 meter is surprisingly accurate, and is very good value for money, especially for home labs and (I feel) for schools too. The Bluetooth logging capability works very well. There’s not much not to like about this product. I loved that the important measurements were accurate and fast, and the meter even performed well for the lesser-used ancillary features such as capacitance and frequency measurement.
The resistance measurement is reasonable, I wish it were faster, and the continuity check definitely isn’t anything to write home about. I wish the AC measurement bandwidth were higher, but for the price, I think it’s still a very attractive multimeter, as long as these things are known.
With the excellent measurement performance, very clear display and Bluetooth capability, and ease of use, I think this is an excellent product.
Thanks for reading!
