BSIDE ADM01 Multimeter

BSIDE ADM01 MultimeterImportant: before reading this review, please read this important safety information.

Overview

The BSIDE ADM01 is a compact multimeter that is widely available on eBay and elsewhere. I first reviewed it back in June 2016 on the Golborne vintage radio forum; this updated version comes after a year of use. At the time of writing, it can be found for just under £9 delivered.

It's a fairly basic unit that appears to be derived from a model made by Mastech - the MS8233D. It's often seen with Hyelec branding, in bright yellow rather than blue.

This is a simple 2000-count auto-ranging meter with 0.5% basic DC accuracy. It includes continuity, diode test, and one frequency range (up to 20kHz). There is also a microamp range - something that is missing from many meters. In addition to the rotary selector, there are four buttons: FUNC, HOLD, MAX and backlight. The meter uses a 9V PP3 battery (not included).

In terms of safety, it is rated at 600V CAT II. Obviously, that won't be independently verified, but at least it's a moderately realistic claim.

Unboxing

Out of the box, first impressions are positive. The manual is reasonable, and the leads look OK. As you unwrap those, you find that they are very stiff compared to the silicon test leads that are normal for more expensive meters, and the probes are hard plastic that is much more slippery than the "soft-touch" finish that Fluke and others use. But, a lot better than the death-trap leads you get with the sub-£5 meters. They are about 95cm long, which is about a foot shorter than the leads that come with Fluke multimeters. They have removable covers that cover the whole of the tip, plus covers in the 4mm plugs - presumably to prevent the metalwork scratching anything in transit - and are rated to a claimed 1kV CAT II, and 10 amps.

BSIDE ADM01 - box contents

The meter itself is tiny. It feels very solid, and the holster fits well. The mode switch is positive in action, but a bit "clicky" and stiff to turn. The 4 buttons are horrible - hard plastic acting on cheap tact switches that are far too stiff in operation. There is a tilting bail but it doesn't provide much stability against switch rotation and button presses, or indeed against movement caused by the stiff leads. On the back, the holster includes moulded sections to store or use the probes.

BSIDE ADM01 - rear view of
      the holster

Operation

Operationally, it's OK, but there are a couple of annoyances. First, the combined diode test and continuity mode defaults to the former. That really needs to be the other way around as you'll use continuity more than diode test. To change mode, press "FUNC.".

Next, the backlight is nice and bright, but it only stays on for 15 seconds! And you have to hold the button for 2 seconds to persuade it to come on in the first place. I don't see the point of the delay, as it's not a secondary function on a button that does something else with a brief press.

The "FUNC." button switches between AC and DC on the current ranges - the default is DC, which is good. The Fluke 87V does the same, but AC is the default - that still catches me out occasionally.

One big problem is the sharing of the positive input terminal between milliamps/microamps and the usual modes of volts, Ohms, etc. This means that if you accidentally turn the mode switch to a current setting while measuring a voltage, you might blow the internal fuse (or worse). Of course, there isn't really space to have a 4th terminal on the unit, and it is nice to have the microamp range, so it's a fair compromise. You just need to get in the habit of checking and double-checking, which is not bad thing...

The terminals are spaced at the industry-standard 19mm, so adaptors will fit them.

Auto-ranging is very quick on Volts, and a bit slower on Ohms (but still very reasonable). But there is no manual range option. That's a shame - normally auto-ranging works well, but occasionally it needs to be overridden. I'd happily swap the "HOLD" button for a range button.

The unit is quick to settle on a reading on all functions apart from Ohms, where very occasionally it can be painfully slow - like 5 to 10 seconds! It doesn't seem to be an auto-ranging problem, as changing from 5k to 10k (using a decade box) doesn't require a range change.

DC accuracy is excellent - well within specification on the lower ranges (so far only tested up to 60V). On current it's almost as good - though still comfortably with within spec - and it beeps at you if you exceed the maximum current for the selected function, which is useful.

BSIDE ADM01 - excellent DC
      accuracy

On DC volts, there is an overshoot issue: the first reading displayed is a couple of volts higher than the correct value. This means that if you measure 18V, the unit will auto-range to the next higher range and show you 18.0V rather than 18.00V. Not good...

The MAX function is interesting at this price point. I compared it to the (rather more useful) MIN/MAX function on my Fluke 87V, and found that it's fine for slowly changing voltages, but doesn't capture narrow peaks as effectively as the Fluke. By "narrow", I'm talking about the sort of speed I could rotate the stiff and heavily damped voltage knob on my ancient PL320 bench power supply - so not very narrow at all, really. Often, the BSIDE recorded a value that was 2 or 3 volts less than the Fluke. Like any tool, it's important to understand its limitations!

AC measurements use the expected average detection, so read incorrectly with non-sinusoidal signals. Frequency response varies with range - on the 2V range, the -3dB point is 17kHz and it falls away after that as you'd expect. BUT, on the 20V range, it started to over-read at ~4kHz! With a 5V sine wave applied, it peaked at 190V at 170kHz! I suppose you could argue that it's better to over-read than under-read, but I was quite surprised at this - clearly a problem with the attenuators.

On AC current, it was fine. Decent accuracy and no HF lift problems...

Frequency measurements were disappointing - which is a surprise in this day and age. When we take it apart, we'll see why...

BSIDE ADM01 frequency measurements
Test Frequency Reading
50Hz -0.01kHz (yes, minus!)
500Hz 0.46kHz
1kHz 1.00kHz
5kHz 5.04kHz
18kHz 18.08kHz

Those measurements were taken with a 5V RMS sine wave. I found that the sensitivity was much better than the 0.8V spec - at 1kHz, it worked down to 75mV RMS.

The diode range is limited to around 1.5V, so it won't light an LED. Given that there is 9V to play with, that's a bit of a shame. Continuity is non-latched, and works at around 10Ω and less, not the 100Ω quoted in the manual.

Current consumption from the PP3 varies between 2.1mA and 2.7mA. The buzzer takes about 23mA, and the backlight takes 15mA. The low-battery indication comes on at 6.1V.

Teardown

First step - remove battery cover/tilting bail, and then the holster (easier said than done!):

BSIDE ADM01 - holster
      removed

Inside, a single PCB. For a cheap meter, it's quite reasonable at a glance. It's good to see ceramic fuses rather than glass. Obviously at this price point they are standard 250V types rather than HRC types that could easily cost more than the entire meter. There are even signs of input protection - we'll have a closer look in a moment.

BSIDE ADM01 - inside view

Undo 4 screws to remove the PCB:

BSIDE ADM01 - underneath the
      PCB, showing the mode switch

Let's look at the PCB in more detail, starting with the top:

BSIDE ADM01 - top view of the
      PCB

Here we can clearly see the OEM model number (MS8233D) on the silk-screen. Note the unpopulated components in the top-left of the picture, which are for the contactless voltage detection that the original Mastech has.

There are no isolation slots routed in the PCB, nor are there shields between the naff pressed terminals - exactly what one expects at this price point. At first, I thought it was good that the terminals have two attachment points to the PCB, but then I realised that the rear of the case doesn't support the terminals at all, so it's just the solder that resists the force from inserting the probes. It would be worth checking for dry joints on those every now and again.

Looking at the input circuitry, we can see that a spark gap is missing, despite being mentioned at least twice in the manual. There is a pair of PTC thermistors for protection. At first glance, the spacing on the PCB looks reasonable, but there is a massive howler on there - look for R1A and R1B. These MELF resistors are 5M each, and are in series to give 10M - and the other end of this goes straight into the IC. The left hand ends (green bands) are only separated by about 2mm, but the full input voltage will be present across this gap, so if a spark jumps this, the energy will damage the input stage of the IC. Fail.

BSIDE ADM01 - resistor
      issue

The clearance between the right hand end of R1A and the via and track that leads to R26 is also rather tight.

Moving down, we can clearly see the current shunts (R49, R48, etc). Note that VR4 calibrates the 10A range.

To the right of the shunts are two SO-8 packages. These are used for the frequency measurements, and are a TL062 dual op-amp and a 7555 timer! The circuit is a F to V converter, calibrated by VR3, and AC-coupled by the large film capacitor. This explains why the frequency measurements are so poor - normally a "proper" digital counter circuit would be used...

The main IC is a Fortune Semiconductor FS9952 in COB form, with a 4MHz crystal. U2 is a LR8503 voltage regulator. The MELF resistors (R2-5) are range-switching, working with the 10M combination seen earlier. Note the poor hand soldering on the tact switches and wires, and note also the flux residue. I did scrape some of it away around the positive input socket before putting it back together.

From a look at the PCB and the datasheet, it appears that VR1 adjusts the voltage reference in the IC and VR2 adjusts the AC calibration. D1 is part of the rectifier, which makes use of 2 op-amps inside the IC. One day, I plan to positively identify each of the pre-sets.

BSIDE ADM01 - underneath the
      PCB

Looking at the rear of the PCB, the mode switch is exactly as expected - no gold plating at this end of the market! There are the usual ball bearings and springs to provide the detents. Note the covering of silicon grease around the switch contacts. The soldering of the battery connector lacks a certain elegance!

Conclusions

For the money, a solid basic multimeter. Having used it for a while, it's been well-behaved enough. I'm not sure I'd use it to measure mains on the bench - and definitely not in my consumer unit - and I'd also be cautious measuring HT in valve equipment, given the problem with R1A/B described above, but it's worth saying that while the meter might not survive a high voltage, it seems no more likely to damage the operator than all the other multimeters I've examined recently.

It's a shame the frequency counter is so poor. The near-identical ADM02 trades that for temperature measurements - and as well see, is much better as a result.

On the upside, I do like the separate rubber holster, which I believe makes it a physically robust meter. The display is clear, with excellent contrast and a wide viewing angle. Overall, a decent step up from those horrid DT-830 types.