Hi, Welcome to another Cichlid Teardown! This time we've got the cichlid multimeter. We haven't had a cyclic multimeter before. This is the SDM 305 Five Bench multimeter. Specifically, this is the 305 Five A model and I believe.

The only difference between the a model that I've got here and the three and the much cheaper 305 five is that this one has a GPIB option. and that's it now. street price of this thing. For the A model that I've got here, it's about six hundred and thirty-odd U.s.

dollars. Now that's pretty pricey, so I wouldn't be getting the GPIB version of this unless you absolutely must have the GPIB option. You're much better off going for just the 305 5a and it's street. Prices currently are 422 bucks on special.

I Was able to find this thing for US dollars different in other countries and different currencies of course, but this is a five and a half digit art meter. It's a two hundred and forty thousand cow, so it's not like six hundred thousand count or anything like that. So twenty two hundred and forty thousand count. A little bit unusual: 0.01 five percent DC Basic accuracy class instruments, so its specs aren't really going to set the ball on fire.

Hundred and fifty yard samples per second, which is kind of sort of. you know, not too bad for a bench multimeter. It's not like the higher end ones, for example. So it sits in this, sort of, you know, almost no-man's land between.

like the you know, the high end agilent bench multimeters for just under or just over a thousand dollars. And you know a decent high end handheld multimeter for example, which you can get five and a half digit multimeters. You don't have to go to a bench multimeter like this to actually get five and a half digits, but a lot of people prefer the bench meters because they sit on the bench. they are always there.

They've got a nice big graphical display on the thisn thing and this thing's got trend plot II and everything else. Very similar functionality to the Agilent bench meter that we've seen before, and I'll show you a comparison at the end because it's absolutely hilarious. But of course, the downsides of bench multimeters? They are tied to the bench and generally they're not going to have the same sort of import protection as a handheld multimeter said not designed to be used in the field. Hence, we're only looking at Cat to 600 volts and Cat 1000 volt rating.

That's very typical over bench multimeters, but of course one of the other advantages of bench multimeter you typically get. And of course you do get in here the four wire measurement so you can do for wire. Ohms. So I've got the two extra sense terminals here.

very nice. Anyway, we'll power this puppy up at the end. let's have a look at it. It feels like looks and feels like a reasonable quality.

a bench meter. You know the no problem with the buttons. The banana plugs look half reasonable and it's a nice little. It's not too deep, it is quite shallow in that respect so it doesn't take up too much bench depth selectable 110 or 240 volt operations so there's no worries about buying it in a particular country.

Now it's got lamb built-in and USB host as well. It's got external trigger because you can sort of. you know, use these for a bit of automation and it's got an extension card option. Now like that must be I'm presuming the GPIB option, but this is the A model and according to the according to the datasheet and websites I've looked at, the A model is supposed to have GPIB that's where you pay extra for the A, but there's nothing there.

so this one might be an oddball one. this is. you know, like got this directly from signaling that like it's a think it's a demo unit or something. So I'm not exactly sure what's going on there.

anyway. there's our white ten-hour fuse on the back. so let's take this puppy apart and I have a look. Oh the Volt nuts of course.

want to know what's references in there? Is it going to be? Yeah, you know you're old school. They've got some thread lock on there that's nice. Is it going to be your old school? Lm3 Who? Cal Sticker. Dull.

It's busted. Who cares? Is it going to be your old school? LM 399 or is it going To be Yes. Something different. Alright, let's pop the hood on this and see what we've got.

Oh, we're in like Flynn We can see old-school looking transformer in that thing Wow So it looks like we've got just a linear power supply and the voltage tap is just a different tap on the transformer there. But like I don't have to go any further. It's all exposed right there, ready for us. Let's take a look.

Oh yeah, look at that. There's the trademarks Siglent Rust I'm sure they do have a trademark on that. No worries whatsoever. Yep, Rust aplenty and that's the thing.

The first thing you notice about this is just like the cheap quality and feel of the metalwork and the rust. just you know, and it's just the icing on the cake there. We've got a little cheap US fan in here and what's it doing? It's you know. we've got some vents here on the other side, but it's blocked by the transformer you know may turn through here and it's just like yeah, do they even need a fan on something like this I Yeah, jeez.

I Don't know. Anyway, yeah, it just feels. it just looks and feels pretty cheap and just kind of like, you know, slap together I'm not gonna say amateur, but it's just not a high quality bit of kit if you put the I know it's not the same price bracket as the Agilent, but if you put the two side-by-side it's chalk and cheese. At least they have gone to the effort to actually the ribbon cable going over here going over to the front panel.

At least they haven't gone to the effort to put in this insulating shield on here, but why they had to run it on on that side and why they just couldn't? You know, you know the system designers couldn't actually move the connector over to the low voltage side here. I Don't you know? like I don't know, it's it's almost as if you know bit of an afterthought. Oh, we have to put the connector over here. Oh well, we'll just punch a hole in here, run it over.

we'll just put some insulating stuff on here and you know, like it just seems a bit clergy and then our earth connection here is just a little bit of a it's not loosey-goosey but it's not tied Eva it's just a spade lug you know, like give me a proper you know shake proof washer and everything. I Don't like that and at least they have bent the metal work over there that so there's no sharp edges on that tight cable Glen there. So that's all right. and it's just funny they've got to let the fan cut out here.

It's like we weren't sure whether or not we'll put the fan here or over there. It's just you know, lack of systems engineering and as I said, we've got a linear power supply. He doesn't need much power, so hence, why do you know, couldn't they have got away without using a fan? It'd be interesting put the thermal camera on this thing later. But anyway, small little light PCB mount and heatsink.

It's not flapping around in the breeze. It's actually one of the proper stud ones that are soldered onto the board. So nice. They've got Lille on brand caps, so you know you're they've got separate taps.

of course this one. This is the digital processing board, which we'll take a look at. It's got its own AC transformer tap electrically isolated from the input acquisition side of things. So it's got its own little full wave bridge rectifier down there.

It's got another Lille on cap, but that's probably like a, you know, a 3.3 volt that looks like a switching supply over there to generate all the you know, probably 1.2 volts, 1.8 volts, or whatever is required for the processor down here. So that's all. That's all hunky-dory But yeah, once again, it looks like we've got a couple of taps here. We've got a couple of two, possibly two full wave bridge rectifiers there, and hence the two different caps.

And then we've got our digital isolation between the processor board and the acquisition board. Here That's this little flat flex ribbon cable. There's a we might actually take a look at. It's one of those analog devices are puppies.

so that's an opto isolator. Got another opto isolator there? You'll notice that the big cut out there on the board you can see cut out of the ground plane and everything else. So they've got nicely isolated all hunky-dory and there's our front end side of things. We'll take a closer look, but the first thing I Noticed of course is the thin film resistor network here from Marquette, Ik.

They're one of the top art makers so they're not unlike you know, fluke and Agilent who who rolled their own ones of course. So they get Khattak to make it so no worries there at all. that's top notch. Then we've got some.

Looks like we've got ourselves a high voltage resistor network here. They're You know they're not. They're not using those for their power dissipation, those large case resistors. They're using those for the large voltage our string.

So that's a high voltage string. That's why they've got them all in series. They're not that big for power dissipation reasons and you can see that they've got the gold trace going around there. That's our wire guard trace for leakage, so that's alright.

I Could see a couple of more guard traces down in here. I Might get the macro lens and take a look at and this high voltage just string here. Actually, your father wires follow the money. It goes up here goes up here goes up here.

There are sense terminals, There are positive and negative sense terminals. so there are positive and negative sense resistor change like that. So they're doing that. of course.

for a high voltage. Our overload overload protection. Because you know you people could accidentally mix up those connectors on the front. and they do.

So yeah, you've got to protect about against some idiot plug in, you know, 240 volt our mains into these sense terminals. But check it out. We have ourselves a genuine budge Look at this. You know this big power resistor which is according to the footprint down there is supposed to be a surface mount job' and they've got their flying lead coming over to this.

PTC I Mean that's just horrible. There's no excuse for that. in a bit of production gear like this. There's just yeah, absolutely no excuse.

Geez. I Mean come on. and this is rather unusual. Look at that that looks like a ceramic resistor network, but almost looks like like it's a BGA package or or something like that.

and there's like almost like a dip. Alternative part that is, that is bizarre. What on earth are they doing there? Anyway, the input protections. Not to why? Shabby here.

This red wire is coming from our import banana plug. Then we've got a couple of guests discharged two tubes here. a couple of big beefy looking mouths. no worries whatsoever.

Then we've got a nice-looking big-ass relay. but I'm not entirely sure what they're what they're switching their. Hmm, they got very beefy diode bridge protection there, which I've done a video on. input protection arrangements and things like that.

You'll typically find a diode bridge for clamping protection and oh yeah, that's a that's a decent Beast And there are current sensor resistors right down in there because our white our white cable coming over here is our current input and it goes off to these two cables that goes off to the 10 amp fuse connector on the back. So I'm not sure why they're running this. They've got a ceramic fuse in their little M 205, but I don't you know? which isn't encapsulated. Very nice.

But yeah, why they've got that secondary fusing there? Because this doesn't have a low current range. It's only got one single 10 amp current input and that's it. So yeah, I'm not sure why they ran the current input this a white wire there onto the board. They soldered that directly and they got.

Then they've got some Spade loads coming over here to the fuse. Why not just run that? You know? if you're gonna fuse it on the back here, why not just run that fuse wire straight over to here and then just have a single wire running back? Don't I get it? And I wonder what's under the shield? it can is that the it seems too near to the input here too to be like the voltage reference. So I reckon that's probably like the AC stuff. the possibly the true RMS converter.

so we'll pop the hood on there. Looks like there's a screw accessed from the other side. but yeah, I can't see your traditional LM 399 on here. It's not.

You probably don't wouldn't expect to find LM 399 class voltage reference. You know, instrument of you know, five knife digit meter of this class. But yeah, we'll find that eventually. But let's pop the hood on that.

It's near the front end. and I was right. But that's all that's going to be right because just based on its location and the functionality, that's what it had to be. No surprises for finding the venerable Ad 637 true Rms site converter.

So that's just doing the AC range stuff. Bit of a clutch with the two resistors there. they've actually got those soldered together at the same point. Like and there folks is the money shot.

There's our ADC It's an Analogue Devices Ad71 90 24-bit Delta-sigma converter. 4.8 kilohertz conversion rate, four channels. It's got building program boy again. Amplifier: yada-yada-yada Fairly typical of what you'd expect to find in a V.

Enough digit multimeter of course I'm like like fluke and keysight. They haven't like rolled their own you know, dual slope converter and stuff like that. Just used an off-the-shelf Dell to see my good. enough for a 5 knife.

Did you meet it? No worries whatsoever. And there's our voltage reference right next to it. It's the max 6325, the Csa version it's you know, a reasonably sure make reference. It's our 0.5 ppm initial accuracy of 0.02 percent.

but of course, that doesn't matter a rat's arse. It's all about the temperature drift because this thing's got a nominal DC spec of 0.01 5% So actually better than this chips initial spec. And that's possible because they calibrate these things and they adjust them. they program into them the calibration offsets at the factory.

But of course, the 0.5 ppm is only short-term drift. Long-term drift spec sheet says about 30 ppm per thousand hours, so you know it's not going to set the world on fire. but hey, that's a 5 and 1/2 digit meter, so it's good enough. Haven't gone through the calculations and all that really deep into the datasheet.

I'll leave that up to the volt nuts to decide whether or not that's a suitable reference for the claimed specs and everything else and how it compares. I'm sure there's no shortage of people who will be willing to compare this to various other meters on the market, but once again, it's probably not fair to compare it to. And you know a key site or a fluke that costs you know, twice as much or more than this thing. three times more in some cases.

Yeah, you know it. It's good enough for the job I guess. And there's a couple of these in here. these analog devices Ad 86 29 These are fairly schmick chopper amplifiers a zero drift chopper.

amps like I use in my microcurrent. What? I Must say I'm not blown away by the soldering quality in this thing. I Mean, it's not bad, but yeah, you know this lead-free rubbish. But yeah, it's not the best.

it's just a little bit sloppy. a little bit sloppy. Look, you know, excess paste on on that? Where is it? Where's my pointer? Sorry. Can I get my pointer in excess paste on that cap? And you know, like Mm-hmm as I showed you before the guard traces though, they're those gold traces.

they're had the solder mask removed. They're actually providing leakage and contaminant protection between critical traces. So I guess they know they're doing. they're those.

EDG Chips are a dead giveaway. As soon as you see the a DG prefix like that, you know there are. You know, some form of analog switch and there our current shunt resistors for your current shunt resistor fanboys. I Know you're down there.

You can see the serpentine trace on the one on the left there and no surprises for finding just a little life PGA in there that's a lattice market so part really cheap. Really? Yeah, not high-density at all. It started to just be doing the sample. you know, handling the sampling 150 samples per second, probably buffering that and just feeding that across the digital interface.

You can see that that's hooked up directly to the digital I/o So yeah, it's just handling the sampling, not subsystem. And that's pretty much all she wrote on the analog front-end You know it's it's got all the requisite stuff. Um, probably. You know it does the job, does the business.

Can fold it too much for a, you know, a lowish cost, five and a half digit bench meter. Now, as for the processor board here, let's taking a very quick look at. there's not much on, and of course why they've got. There's actually, um, miss in screw holes here.

They've gone to the effort to put them in the PCB I Can actually see that there's threaded studs down in there in the case. but um, yeah, they haven't put the screws in. Why? Rather interesting that there's a populated flat flex connector here, which kind of sort of goes over -. well.

I Don't think it's to do with the digital connection over to the the isolate digital isolated connector over there, but I Think it. You know there are traces running back there. But what things for? I Got no idea and we've got ourselves an Arm Cortex A8 here. This is the Satara processor from RTI System on chips.

got all the requisite stuff. It's got a, you know, a whiz-bang touchscreen, graphics controller, all the rest of it, all the bells and whistles, all that, you know, the hard peripherals, the whole, the whole shebang. So yeah, no surprises. Although I Don't think we've seen a satara process or in another bit of test gear, so it's rather interesting.

and then it is coupled down here to this chip which is upside down so all the electrons are going to fall out. This is a Ddr3 one gigabit dram. So yeah, it's got enough memory to run Linux or whatnot. and there's an unpopulated micro SD card connector down there, so that'll allow them to do you know, boot, programming, development, all sorts of you know weird and wonderful things.

and I'm sure hackers can get in there and make use of that puppy. no worries. And there's not much else exciting going on around here. although we do have a five-pin single inline header up.

there. Could that be some sort of serial monitor interface? Perhaps I Don't know, it's not labeled in any way. There you go. That's pretty much all she wrote inside this thing so you know it's kind of built down to a price, but that's what it is.

It's a cheapish you know, five-and-a-half digit multimeter with you know, reasonable specs and as we'll see in a minute when we pair it up, most of the functionality of the higher-priced are agilent the unit so let's check it out and if we have a look with the floor we can see inside there and you can see the transformer up there. it's at about 35 degrees or there abouts big hot spot there at about 50 I was getting 52 at 52 at one point. There we go almost 53 at one point. So that's a linear regulator up there on the acquisition board.

You can see the processor right down there. It's a little hot spot as you do expect. you know, one of these Cortex thingamajig sore. Whatever they're they require a fair bit and there's a, you know, another there.

Well, there's the heatsink. By the way, there's that large heatsink on the acquisition board so there's nothing doing there. I'm A by the way, I'm pointing towards I'm there talking about what's in the crosshair here. This temperature up here is what's on the crosshair and this is just the min/max By the way, a few people get confused by that.

oh sorry about the glare there. that device down there near the input sockets. that's actually the relay. that's an input switching relay and that's obviously energized.

You can see because it's it's warming up. The only reason that would warm up is because the coil in there is actually energized. So there you go. But apart from that, it's not getting no.

There's no thermal issues there at all. Check it out if there is a more blatant ripoff. I haven't seen it, look at it. Compared to the Agilent R3 double 4 6, 1a which is I've been out for quite a long time now and it's a massively popular.

It's like the benchmark six and a half digit multimeter. It's yeah and practically the best bang per buck on the market. And of course it is not a fair comparison. This thing is like four hundred and twenty two dollars street price.

This thing is like I think slightly over a thousand or the six zero is slightly on is like $900 or something like that. I'll stand corrected on that. but yeah, you know it's like two and a half times the cost and six knife digit meter. it's got.

you know, a much better voltage reference in there, much better design, much tightly, much higher controlled specs. everything else. so really, you know, like not not a fair comparison at all. but look at the user interface.

it is identical right down to the menu options. look number bar me that they even call it's our trend chart which I think might even be a Agilent Keysight. sorry still got the Agilent badge on there. Um, Keysight.

So how about I can't get out of I'm sorry. jeez. I'm still getting over the change from HP to Agilent let alone from Agilent the keysight anyway. I believe Trenchard is actually I think it might be a trademark of Keysight And then they've got the histogram as well and even the stat menus.

It's exactly the same. Everything's in exactly the same position, but the edge layer. The keysight looks a hell of a lot better. The fonts are better, you know it's it's a bigger display and you know it just looks much more polished.

But like, come on, they didn't come about this by accident of course, and you'll notice the key layout is almost exactly the same. Almost. The keysight does actually have our capacitance function Now it's that they've actually added that as a firmware update, which is quite nice. So, but you know they've mixed to fuel the keys up around here, but it's absent achill.

Except of course, the Agilent is a rear or bench multimeter. And when I say real bench multimeter like as in a proper system at Bench Multimeter it's got the front and rear terminals you can actually switch and whereas these siglent, of course is not, you know, designed for proper system rack automation and stuff like that. so it's only got the terminals on the front, which very just a general-purpose lab bench multimeter. You never use the terminals on the back so they go into waste or not.

Something like the Keysight here. But the siglent. Yeah, you know, nothing wrong with not having rear terminals. You're really.

you know if you're by building an automating a test system or something like that where you need a 6 digit meter like this and automate it and you can get rack kits for this so you know can mounting racks and stuff like that, then you know you're not going to be. You know, cheeping out and buying the siglent? You're going to go for the Agilent, which has all the bells and whistles. It has the trust, it has the full support and cost really isn't an issue when you're you know, designing a automated rack system and things like that. And if you go into trend chart here look, you can see that it's the menu options.

once again, identical. They've just copied it. Unbelievable. Well, you know imitation is the sincerest form of flattery, is it not so? Anyway, I've got to avoid turning this thing into a review or whatever.

So yeah, it's just supposed to be a quick teardown. I Always say quick and then it never is I think I've got now been my counter on the camera here. 29 minutes worth of raw footage. So that's going to edit down to, you know, something over 20 minutes.

Maybe doing like 25 minutes or something. So yeah, it's got a few build quality issues and things like that. but yeah, you know it is built down to a price and 422 bucks probably isn't too bad if you're in the market for a you know, a feature-packed five and a half digit bench multimeter and well, it you know it's probably going to do the business. is worth checking out anyway.

You know, don't buy it on spec, you know I get you try and get your hands on one somewhere and you know, give it a demo and stuff like that and see if you actually like it, see if it suits your purposes and stuff like that. But I will show you just one little feature here. it can actually measure voltage and current at the same time. I Don't know if it can actually I calculate power, but you can see that on the it's got a dual display tiny little light secondary display down here.

so I'm displaying that current up on the main display and then the second display. I'm actually displaying the voltage. And of course, you can do this using a common ground so you know we've got a separate and current terminal and a separate voltage input terminal. You can hear it click-click about every second that switches between voltage and current and then updates the display so it's not a simultaneous thing.

It can't do that, but it can actually physically switch between them so that could be handy. It's like I think I did a review of the ancient flick 45 multimeter from back in the 80s and it could eat It did exactly this. so this thing could do it. That might come in handy.

So anyway, if you like the teardown video, please give it a big thumbs up. I Know I've done a lot of teardown videos recently and I've done a lot of siglent and done three siglent teardown videos recently. But hey, I just happened upon these instruments. So, but there are people who love to see the teardown videos.

so if I've got the gear I'm gonna tear it down. You bet your bottom dollar anyway I hope you liked it. Catch you next time you.