BSIDE ADM08A Multimeter

BSIDE ADM08A MultimeterImportant: before reading this review, please read this important safety information.

Overview

The BSIDE ADM08A is a manual ranging multimeter. Now, I'm not really a fan of manual ranging, prefering auto with a manual override for those occasions when the auto ranging is confused by rapidly changing signals. However, a lot of folk strongly prefer manual ranging, so I bought this one with those people in mind.

This meter is different from the usual meters at this price point because of two main features: it's 6000-count rather than the usual 2000-count and it's true RMS. I wonder if it uses the same chipset as the Aneng meters? Like nearly all of these budget meters, the basic DC accuracy is 0.5%.

In addition, there's a NCV (non-contact voltage) detection mode. It also does frequency and capacitance (those two functions are auto ranging) in addition to the usual voltage, current and resistance measurements. There's also continuity and, leaving the worst 'til last, Hfe! A transistor test mode on a DMM is usually a sure sign of a meter where safety was well down the list of priorities, but let's wait and see what we find inside...

Unusually, this meter is powered by 4 AA batteries. That certainly adds to the weight of this unit, but I wonder what needs the extra voltage?

It appears that this is a Peakmeter PM890D.

This meter cost me £12.29 delivered, and arrived from China via tracked post in just 10 days.

Unboxing

As expected, the meter comes with a manual and set of probes. The meter itself is quite large - virtually the same size as a Fluke 87V - and rather imposing in black. By "imposing", really I mean "ugly"! On the plus side, there is a separate holster - like the other BSIDE meters - and at least it won't show the dirt as much as the colourful alternatives!

BSIDE ADM08A - box contents

The probes are a bit bigger than the others supplied with the smaller ADM01/02 meters, and are rated at a claimed 1kV CAT III, and 20 amps. Otherwise, they are much the same - relatively inflexible cable and hard, shiny plastic for the probes. They come with the usual covers at both ends that go straight in the bin (the BSIDE probe tip covers actually cover the whole of the probe, rather than most of the metal to improve the CAT rating). The manual is quite comprehensive, stretching to 24 pages, and the English is pretty good on the whole.

Operational

There are two buttons on this meter; one for changing mode - which does less than normal because this is a manual-ranging meter - and another for hold and backlight. Unlike the ADM01/02 meters, these are a rubber membrane type that feel quite nice to use. The rotary switch is rather stiff and notchy to operate, and could do with being a bit larger. Also, they could have painted the line at the end to more clearly indicate which mode it's pointing to.

Rather than list all the functions and ranges, it's easiest to just look at the range switch:

BSIDE ADM08A - range switch

There is a decent backlight, but in common with most cheap meters, it only stays on for 15 seconds. That's really annoying, especially as you have to hold the button for 2 seconds to get it on. At least the (pointless, as always) hold function doesn't interact with the backlight, unlike the RS14. The LCD viewing angle is pretty good, though if the meter is flat on the bench, you start to notice the unlit segments bleeding through when the meter is pushed back towards the rear of the bench. Nowhere near as bad as the RS14 though.

The NVC detection mode is a bit of a gimmick, and not something I use on a multimeter. This meter has an LED scale across the top of the display, but don't be deceived - despite appearances, there's only actually 3 LEDs behind the lens. I found that if test leads are plugged in, the system is triggered falsely some of the time. There is also a "Live" mode - the idea here is you can apply just one probe to a circuit, and it'll tell you if it thinks it is live. The manual says that holding the probe near to a live conductor should trigger it, but it doesn't seem to for me - I had to make definite contact. I suppose that both of these modes are intended to avoid hazards, but I'm just not convinved I'd ever use them.

The basic DC performance is fine - every test I've tried results in a number that is comfortably within the spec.

BSIDE ADM08A - excellent DC
      accuracy

In common with the Aneng meters, the specified AC bandwidth is 1kHz, and the -3dB point is 3kHz. The low-pass filter ahead of the true-RMS DSP is implemented digitally in the DTM0660 chip used in those meters. With a 100Hz sine wave set to 0.7V RMS, switching it to a square wave of the same peak value gave the expected 1V RMS.

With 1V RMS (sine wave) fed into the 6V AC range, I found the frequency counter read reliably up to about 2.5MHz. In the same range, the minimum sensitivity for 1kHz was about 50mV RMS. In the dedicated Hz position, the sensitivity improved to 30mV at low frequencies (< 100kHz), and at 1MHz, 43mV was needed. Above that, the sensitivity drops off and then basically plateaus. 10MHz needs 1.6V, and I could push it to 69MHz before running out of signal level. This behaviour is very similar to the AN8002.

Unfortunately, the input waveform must cross 0V for the frequency counter to work - either in Hz mode or in the AC voltage function. This means that TTL signals won't register unless you pass them through a capacitor first. This, of course, is the same as the Aneng meters, and further evidence of the DTM0660 chipset.

I did notice some strange behaviour while playing around in the 10-30MHz region - at one point, the meter started beeping continuously, not stopping until I'd changed to a different function. At one point, I got it to the point where a reboot was needed to restore normal behaviour. The amplitude of the applied sine waves would have been in the 5V region - it was obvious enough to upset the IC.

The continuity test is pretty good - sounding at about 30Ω or less. Interestingly, the LEDs used for the NCV detection light up as well to indicate the value of resistance; the red one starts flashing at 60Ω and is solid at 50Ω. When the buzzer sounds at 30Ω, both green LEDs light. I did notice some sensitivity to touch at 40Ω, where if I covered the display with my hand and removed it, the buzzer sounded and the green LEDs lit for a second - presumably the NCV circuitry was having some influence. Not a big problem in practice.

Capacitance also works well, taking about 6 seconds to read the value of a 3300uF capacitor, which isn't bad going. My 180pF test capacitor (177pF according to my Peak Atlas LCR40) is apparently 211pF, so take readings on the lowest range with a pinch of salt, but that is within the spec for the 6nF range (±4% +30 digits). All other measurements made with larger capacitors were much closer to their true value, and all met the spec, which is ±4% +3 digits on all remaining ranges apart from 60,000µF (±5% +3 digits).

The diode test range outputs 3.3V so is useful for testing LEDs.

Current consumption from the 4 AA batteries varies between 0.65mA and 1.7mA in the usual ranges, and rises to 28mA in continuity with the buzzer sounding and the LEDs lit. The backlight LEDs take an astonishing 75mA! The low-battery indication comes on at 5.1V (1.275V per cell, so a bit high), though the meter still gives accurate results on Volts at least (other functions not tested) until it shuts down at a surprisingly low 2.2V.

Teardown

Start by removing the battery cover and holster:

BSIDE ADM08A - holster
      removed

Then remove 4 screws from the rear of the case. Or 2. That's right - 2 of mine were missing! Despite that, the case did feel pretty solid thanks to the holster and the effects of the deep overlap between the two halves, but even so, this is a bit of a QC Fail. I had a really close look once I'd got it apart, and it was clear that the plastic pillars had never seen a self-tapping screw since leaving the mould. A couple of suitable screws were easily found in my junk box.

BSIDE ADM08A - internal view

Inside we find 20mm ceramic fuses for the current ranges and a couple of PTCs. No isolation slots or MOVs, naturally. They went to the expense of a plug in connector for the battery connection. Note the "aerial" used for the NCV function.

The underside of the PCB is as expected:

BSIDE ADM08A - underneath the
      PCB, showing the mode switch

At this stage, the mode switch just lifts out, leaving behind the small springs and ball bearings that provide the detents. Well, in practice, the switch falls out, and the springs and ball bearings get lost. You have been warned! On the upside, this makes it easier to paint the pointer to make it easier to see which mode you've selected...

Let's have a closer look at the PCB:

BSIDE ADM08A - top view of the
      PCB

Here's confirmation of the OEM part number - "PM890D" is clearly visible on the silkscreen, by the Amps jack. Talking of those, while they are the cheap pressed type, note that they fold around the PCB and are installed from this side, meaning that they will resist forces from the action of inserting plugs rather better than the usual arrangement.

The 10M input divider is the usual pair of 5MΩ MELF resistors, and happily this time they arranged rather better than in the ADM01/02 meters. In addition, there is a good selection of other MELF resistors for the dividers and current shunts.

There are no pre-set resistors, but looking to the right, we see an EEPROM next to the COB that will be holding the calibration data, along with a 4MHz crystal. A pair of transistors form a high-speed clamp, and a Holtek HT7530-1 voltage regulator takes the 6V battery voltage and steps it down to the 3V needed by the IC.

BSIDE ADM08A - underneath
      the PCB

This view clearly shows the 3 LEDs for the NCV detection function, along with the transistor tester socket. I don't like to see these on multimeters - it's a worthless function that reduces safety because a multimeter can float to common-mode voltags that are significantly above ground potential. Never leave anything plugged into this!

Notice the heavy track for the 20A range - this is on both sides of the PCB to a large extent with lots of vias joining the traces, but I can't help wondering if it might have been simpler to run it in its entirety on the top of the PCB.

Conclusions

I don't use manually ranging multimeters, so I wouldn't have bought this if I wasn't reviewing it. However, for those who do, this is worth a look for the 6000-count and true RMS features. It's certainly a decent step up from the cheap and nasty DT830 types, and has good continuity and frequency counter modes. For electronics work, the gaps in the current ranges (and the lack of AC microamps) could be a problem. Personally, I don't attach any importance to the NCV mode, preferring a dedicated "pen" type.

I see no evidence to support the rather fanciful 600V CAT IV claim - obviously this meter won't have been independently verified - but for low energy bench work, this meter should do the job. Though if you're looking for a multimeter of this size and don't mind paying a tiny bit extra, the Aneng AN860B+ would be my pick.