23-05-2016, 11:45 PM
And now, the multimeter that started all this - the "RS-14".
The B-Side meters were picked up on the basis of them being a close visual match for the RS-14. Well, as far as you could tell from the pictures on the RS web site. However, the RS-14 is different from B-Side meters. But they have a lot in common...
First, it costs £14.20+VAT at the time of writing - 17.04 all in. In percentage terms, that's quite a step up from £10, but when you think what an entry-level Fluke would cost, it's still ridiculously cheap!
What are the differences?
Firstly, the case doesn't have the separate holster that the B-Side units come with. Instead, the blue sections are that soft-touch plastic that is so common today, and that helps to give the unit a more expensive feel. However, it doesn't add any strength to the case, and I reckon the B-Side meters would perform better in a "drop test" because of the shock-absorbing properties of the holster. And soft-touch plastics can become tacky with age. The underlying plastic in both cases is much the same thickness, and both types of meters feel equally solid - commendably so given the price point.
Side by side, the RS-14 is slightly smaller, although the difference is mostly because of the holster. Not visible here, it's thicker, but that most definitely is because of the holster (that has the probe storage sections moulded into the rear).
Earlier I criticised the rotary switch of the B-Side for being a bit stiff (so therefore hard to change mode with one hand while the unit is stood up on its tilting bail). However, the RS-14 is much worse. On my hardwood bench, it is impossible to change mode without it sliding about the place. On a carpet tile it's better, but you still need to use spare fingers to hold the damn thing still while turning the switch. Really, you need to have it flat on its back. The switch has a rubberised coating to help with grip, and that's very necessary!
Also, when on its back on a hard surface, it slides about all over the place. The only non-slip elements are at the top, so offer no resistance against the rotation of the mode switch. If only they'd put raised non-slip bumps on the bottom as well. The B-Side is much better here.
However, the buttons are much better. Rather than the cheap tact switches, they've used a membrane keypad. Good...
In terms of functionality, the left button does the same with both - changes between AC and DC on current, switching between C and F, switching between diode and continuity. You get the idea. But, the next one changes range with the RS-14. That's good news. You might only need manual ranging occasionally, but when you need it, you need it!
The next button is a combined backlight and Hold button. That's less good - I'll get on to that.
Finally, there is the Max function. As I said before, not especially useful...
The LCD is much bigger, giving larger digits. But the viewing angle is rubbish compared to the B-Side types. If you lay the meter flat on its back - which the stiff switch and hopeless tilting bail more or less obliges you to - then you can hardly read the display because the "off" segments are lit up! It's worse if you're off to the side.
The probes are better. They are the same length, but much more flexible. Not silicon at this price, obviously. They are dual-rated, depending on whether you use the protective covers that obscure most of the probe - in place, they are Cat IV 600V rated (and Cat III to 1000V). Remove these and they are Cat 2 1000V (the same as the B-Side types).
Safety is the big selling point with this meter - it's rated to Cat III, 600V. Of course, this means the Cat IV rating of the probes is moot, as the "weakest link" sets the overall rating. The B-Side meters are only Cat II 600V, so theoretically, the RS meter is safer. To be honest, having done an internal inspection, I'm unconvinced. I think the RS-14 is less likely to damage itself when subject to a voltage surge. But in terms of damaging the operator, which is what the Cat ratings are really about, I'm not sure. Both meters use the same sorts of fuses for current, and both have very similar construction using similar materials. So without independent testing, the jury is out for me. Frankly, if you need to work on an incoming supply, you should be using something rather better than sub-£20 multimeters.
What do these meters have in common?
They both use the same IC. So some of the annoyances of the B-Side meters are equally present in the RS-14. Such as the stupid backlight behaviour. You have to hold the backlight button for 2 seconds to persuade it to come on, and it only stays on for 15 seconds! But with the RS-14 it's worse, as they've joined the backlight and Hold pins to the IC, meaning that a brief press of Hold engages the hold function. But the long press needed to get the backlight on also engages Hold, meaning that once you've got the damn thing to light up, you have to press the Hold button again to get it out of Hold mode. You'd get use to it, but I was surprised at how annoying that was.
By way of example, the Fluke 87V combines the backlight function with the Hi-res mode. A brief press controls the backlight, and a long press engages Hi-res. As you press the button initially, the backlight comes on (or more precisely, it changes to the next available state - on dim, on bright, or off). But if you hold the button long enough to put it into Hi-res mode, the backlight reverts to the mode it was previously in because it's obvious that you didn't want to change the backlight; you wanted to change resolution. Might seem trivial, but as someone who does a bit of UI design, it's the sort of detail I notice and appreciate when it's obviously been thought about.
The backlight is fine, but not as bright as the B-Side models. Interestingly, the ADM02 is considerably brighter than the ADM01, but that's almost certainly because they aren't too strict about the type of LEDs they purchase for these!
Teardown
Removing the battery access door also gives you access to the fuses, although I'm not sure what sort of tool you'd need to remove them! And look carefully through to the PCB, near to the battery wires. Yes, that is a pre-set resistor there - mind the lead doesn't trap itself in there and alter the setting!
Internally, they are quite different:
The first thing I noticed was the 10A current shunt. There's no preset, unlike the B-Side types, and "calibration" was performed using a pair of side-cutters. That surprised me!
Next, there's a fair few leaded components. All the divider resistors are TH types, mostly stood up on end (and need straightening up!). The obvious improvement over the B-Side meters is the use of leaded components in the 10M input divider - remember how I pointed out the possibility of a spark jumping the 1.5 or 2 mm between the end-caps of the MELF resistors (R1A and R1B)? Here, that prospect has been eliminated (see R27 and R28 - the 5M, 0.5% types - though I note the B-Side resistors are 0.25%). Thumbs up!
Also, something has actually been fitted in the position labelled SG. It's a MOV - an 820V type. Nothing stopping you retro-fitting one of these to your B-Side if you like!
Like the B-Side variants, the main IC runs at 4MHz. The one electrolytic capacitor is made by Chang - quality
The meter itself is a DT-914, which appears to be made by CEM
Operation
In use, the RS-14 has the same "overshoot" issue as the B-Sides. So, set your PSU to 18 volts or thereabouts and dab the probes on the output, and it'll jump to 18.0V rather than 18.00V.
But fortunately, it doesn't suffer from the same AC over-reading as you increase the frequency. Both my B-Sides do this, so it's not a fault with the first one I bought. The RS-14 just falls away as you'd expect - the -3dB point being approx 7.5kHz (well, on the 2V range - I didn't check the others exhaustively).
Interestingly, the RS-14 has an AC mV range that is easy to miss if you don't spot it in the manual. It will never auto-range into that range, but if you press the Range button enough, you'll get it. Because there is no Range button on the B-Sides, that mode is not available (even if it actually exists).
Annoyingly, the Diode/Continuity function defaults to Diode, just like the B-Side meters. It's non-latching again, which is fine if that's all you're used to - but once you've used a Fluke or similar, it's tough to go back. The threshold is 50 ohms. Amusingly, the RS manual says both <100 ohms and <30 ohms! The ADM01 was measured at 10 ohms, but the ADM02 is 40 ohms (the manual says <100 ohms). Clearly, this is not a precisely controlled parameter!
The slow resistance readings noted with the B-Side is also present. It's a bit hard to describe, and it's a bit inconsistent. It's not related to the auto-ranging, which is fast. I hooked up a couple of decade boxes to a B-Side and the RS-14, and played around for a good 10 minutes - on average, they're basically as bad as each other, but the RS-14 is perhaps slightly quicker.
Verdict
So, which should you buy?
Forget about the ADM01 with its useless Hz range - it's a 2-horse race between the ADM02 and RS-14.
Of the negatives I've raised, most of them are common to both - they both use the same IC and are electrically very similar.
The RS-14 is more expensive, but has the backing of RS. It's Cat III rather than Cat II, for what that's worth in the context of sub-£20 meters which haven't been independently verified. The RS-14 is slightly smaller, but slips around on the bench. The probes are better - quite usable. A working battery is included. The buttons are nicer.
Against that, the ADM02 is cheaper, but just as well built (apart from the probes, which really are too inflexible for day to day use). I prefer the separate holster, and I think it results in the ADM02 being the more rugged of the two.
On the bench, the main problem with the RS-14 is the display. The larger characters do not compensate for the poor viewing angles when on its back. But the tilting bail - combined with the over-stiff rotary switch - cause a problem. A solution might be a separate stand - perhaps a few scraps of timber to hold the meter at a suitable angle, with sides to stop the meter rotating when you operate the switch. Fine if you like woodwork and you have the time, I suppose...
So on balance, I'd buy the ADM02 unless the slightly smaller size of the RS-14 tips the balance for you. At this price point, both are disposable, but both represent a worthwhile step up in quality, accuracy, functionality and safety from the sub-£5 meters out there.
Will I buy a batch of RS-14 meters to replace the 30 year old Fluke 75s that we have in our Funds lab at work? No. We're better off hanging on to the old Flukes. But I might buy some to replace the AVO 8s that we still use (because some transistor experiments require the measurement of ~50uA, which the Fluke 75 doesn't do brilliantly).
Again, either of these offers so much more than the sub-£5 meters
The B-Side meters were picked up on the basis of them being a close visual match for the RS-14. Well, as far as you could tell from the pictures on the RS web site. However, the RS-14 is different from B-Side meters. But they have a lot in common...
First, it costs £14.20+VAT at the time of writing - 17.04 all in. In percentage terms, that's quite a step up from £10, but when you think what an entry-level Fluke would cost, it's still ridiculously cheap!
What are the differences?
Firstly, the case doesn't have the separate holster that the B-Side units come with. Instead, the blue sections are that soft-touch plastic that is so common today, and that helps to give the unit a more expensive feel. However, it doesn't add any strength to the case, and I reckon the B-Side meters would perform better in a "drop test" because of the shock-absorbing properties of the holster. And soft-touch plastics can become tacky with age. The underlying plastic in both cases is much the same thickness, and both types of meters feel equally solid - commendably so given the price point.
Side by side, the RS-14 is slightly smaller, although the difference is mostly because of the holster. Not visible here, it's thicker, but that most definitely is because of the holster (that has the probe storage sections moulded into the rear).
Earlier I criticised the rotary switch of the B-Side for being a bit stiff (so therefore hard to change mode with one hand while the unit is stood up on its tilting bail). However, the RS-14 is much worse. On my hardwood bench, it is impossible to change mode without it sliding about the place. On a carpet tile it's better, but you still need to use spare fingers to hold the damn thing still while turning the switch. Really, you need to have it flat on its back. The switch has a rubberised coating to help with grip, and that's very necessary!
Also, when on its back on a hard surface, it slides about all over the place. The only non-slip elements are at the top, so offer no resistance against the rotation of the mode switch. If only they'd put raised non-slip bumps on the bottom as well. The B-Side is much better here.
However, the buttons are much better. Rather than the cheap tact switches, they've used a membrane keypad. Good...
In terms of functionality, the left button does the same with both - changes between AC and DC on current, switching between C and F, switching between diode and continuity. You get the idea. But, the next one changes range with the RS-14. That's good news. You might only need manual ranging occasionally, but when you need it, you need it!
The next button is a combined backlight and Hold button. That's less good - I'll get on to that.
Finally, there is the Max function. As I said before, not especially useful...
The LCD is much bigger, giving larger digits. But the viewing angle is rubbish compared to the B-Side types. If you lay the meter flat on its back - which the stiff switch and hopeless tilting bail more or less obliges you to - then you can hardly read the display because the "off" segments are lit up! It's worse if you're off to the side.
The probes are better. They are the same length, but much more flexible. Not silicon at this price, obviously. They are dual-rated, depending on whether you use the protective covers that obscure most of the probe - in place, they are Cat IV 600V rated (and Cat III to 1000V). Remove these and they are Cat 2 1000V (the same as the B-Side types).
Safety is the big selling point with this meter - it's rated to Cat III, 600V. Of course, this means the Cat IV rating of the probes is moot, as the "weakest link" sets the overall rating. The B-Side meters are only Cat II 600V, so theoretically, the RS meter is safer. To be honest, having done an internal inspection, I'm unconvinced. I think the RS-14 is less likely to damage itself when subject to a voltage surge. But in terms of damaging the operator, which is what the Cat ratings are really about, I'm not sure. Both meters use the same sorts of fuses for current, and both have very similar construction using similar materials. So without independent testing, the jury is out for me. Frankly, if you need to work on an incoming supply, you should be using something rather better than sub-£20 multimeters.
What do these meters have in common?
They both use the same IC. So some of the annoyances of the B-Side meters are equally present in the RS-14. Such as the stupid backlight behaviour. You have to hold the backlight button for 2 seconds to persuade it to come on, and it only stays on for 15 seconds! But with the RS-14 it's worse, as they've joined the backlight and Hold pins to the IC, meaning that a brief press of Hold engages the hold function. But the long press needed to get the backlight on also engages Hold, meaning that once you've got the damn thing to light up, you have to press the Hold button again to get it out of Hold mode. You'd get use to it, but I was surprised at how annoying that was.
By way of example, the Fluke 87V combines the backlight function with the Hi-res mode. A brief press controls the backlight, and a long press engages Hi-res. As you press the button initially, the backlight comes on (or more precisely, it changes to the next available state - on dim, on bright, or off). But if you hold the button long enough to put it into Hi-res mode, the backlight reverts to the mode it was previously in because it's obvious that you didn't want to change the backlight; you wanted to change resolution. Might seem trivial, but as someone who does a bit of UI design, it's the sort of detail I notice and appreciate when it's obviously been thought about.
The backlight is fine, but not as bright as the B-Side models. Interestingly, the ADM02 is considerably brighter than the ADM01, but that's almost certainly because they aren't too strict about the type of LEDs they purchase for these!
Teardown
Removing the battery access door also gives you access to the fuses, although I'm not sure what sort of tool you'd need to remove them! And look carefully through to the PCB, near to the battery wires. Yes, that is a pre-set resistor there - mind the lead doesn't trap itself in there and alter the setting!
Internally, they are quite different:
The first thing I noticed was the 10A current shunt. There's no preset, unlike the B-Side types, and "calibration" was performed using a pair of side-cutters. That surprised me!
Next, there's a fair few leaded components. All the divider resistors are TH types, mostly stood up on end (and need straightening up!). The obvious improvement over the B-Side meters is the use of leaded components in the 10M input divider - remember how I pointed out the possibility of a spark jumping the 1.5 or 2 mm between the end-caps of the MELF resistors (R1A and R1B)? Here, that prospect has been eliminated (see R27 and R28 - the 5M, 0.5% types - though I note the B-Side resistors are 0.25%). Thumbs up!
Also, something has actually been fitted in the position labelled SG. It's a MOV - an 820V type. Nothing stopping you retro-fitting one of these to your B-Side if you like!
Like the B-Side variants, the main IC runs at 4MHz. The one electrolytic capacitor is made by Chang - quality
The meter itself is a DT-914, which appears to be made by CEM
Operation
In use, the RS-14 has the same "overshoot" issue as the B-Sides. So, set your PSU to 18 volts or thereabouts and dab the probes on the output, and it'll jump to 18.0V rather than 18.00V.
But fortunately, it doesn't suffer from the same AC over-reading as you increase the frequency. Both my B-Sides do this, so it's not a fault with the first one I bought. The RS-14 just falls away as you'd expect - the -3dB point being approx 7.5kHz (well, on the 2V range - I didn't check the others exhaustively).
Interestingly, the RS-14 has an AC mV range that is easy to miss if you don't spot it in the manual. It will never auto-range into that range, but if you press the Range button enough, you'll get it. Because there is no Range button on the B-Sides, that mode is not available (even if it actually exists).
Annoyingly, the Diode/Continuity function defaults to Diode, just like the B-Side meters. It's non-latching again, which is fine if that's all you're used to - but once you've used a Fluke or similar, it's tough to go back. The threshold is 50 ohms. Amusingly, the RS manual says both <100 ohms and <30 ohms! The ADM01 was measured at 10 ohms, but the ADM02 is 40 ohms (the manual says <100 ohms). Clearly, this is not a precisely controlled parameter!
The slow resistance readings noted with the B-Side is also present. It's a bit hard to describe, and it's a bit inconsistent. It's not related to the auto-ranging, which is fast. I hooked up a couple of decade boxes to a B-Side and the RS-14, and played around for a good 10 minutes - on average, they're basically as bad as each other, but the RS-14 is perhaps slightly quicker.
Verdict
So, which should you buy?
Forget about the ADM01 with its useless Hz range - it's a 2-horse race between the ADM02 and RS-14.
Of the negatives I've raised, most of them are common to both - they both use the same IC and are electrically very similar.
The RS-14 is more expensive, but has the backing of RS. It's Cat III rather than Cat II, for what that's worth in the context of sub-£20 meters which haven't been independently verified. The RS-14 is slightly smaller, but slips around on the bench. The probes are better - quite usable. A working battery is included. The buttons are nicer.
Against that, the ADM02 is cheaper, but just as well built (apart from the probes, which really are too inflexible for day to day use). I prefer the separate holster, and I think it results in the ADM02 being the more rugged of the two.
On the bench, the main problem with the RS-14 is the display. The larger characters do not compensate for the poor viewing angles when on its back. But the tilting bail - combined with the over-stiff rotary switch - cause a problem. A solution might be a separate stand - perhaps a few scraps of timber to hold the meter at a suitable angle, with sides to stop the meter rotating when you operate the switch. Fine if you like woodwork and you have the time, I suppose...
So on balance, I'd buy the ADM02 unless the slightly smaller size of the RS-14 tips the balance for you. At this price point, both are disposable, but both represent a worthwhile step up in quality, accuracy, functionality and safety from the sub-£5 meters out there.
Will I buy a batch of RS-14 meters to replace the 30 year old Fluke 75s that we have in our Funds lab at work? No. We're better off hanging on to the old Flukes. But I might buy some to replace the AVO 8s that we still use (because some transistor experiments require the measurement of ~50uA, which the Fluke 75 doesn't do brilliantly).
Again, either of these offers so much more than the sub-£5 meters
