Building a better multimeter...

[mikeselectricstuff]

The post about whether Rigol should do a DMM got me thinking.
Handheld DMM functionality has hardly changed in the last decade or so, maybe more, yet many other areas of testgear (scopes, AWGs) have improved by an order of magnitude in terms of price vs. performance.
More fancy features only tend to appear in higher end models, as manufacturers want to protect their full product range to compete with similar models from competitors.

However what if a new player decided to enter the market, and design a new DMM from the ground up with a focus on maximum useful features in a  midrange handheld DMM. Let's say in the $200 region.

Here's my list of what I think would be useful and doable without making things much more expensive:

Simultaneous voltage and current measurement (non- isolated with common ground, i.e. same as traditional DMM connectors), with power (simple V*I) display. Cost : this is basically the addition of a multiplexer.  Don't mind if reading rate is a little slower in this mode.

uCurrent-like low-current performance. Just add a chopper-amp. Not too bothered if accuracy is slightly lower. Anyone who needs to measure current draw to better than 1% can pay extra for that.  Cost : maybe $2

Bluetooth connectivity for output of readings. Cheap nowadays, and ideally BLE/Smart/4.0 so it can spit out readings with minimal power draw. Possibly an option by plugging in an internal module (not the ugly external lump from Agilent). Avoids need for proprietory interface cables, inherently isolated and enough range for across-the-room operation.

Variable continuity-test threshold, option to beep on open, very fast (<20mS) with optional stretch.  Maybe 2-level beep, for two thresholds to distinguish open/resistive/short. Option to flash backlight for use in noisy environments. Negligible cost

Very low resistance mode, using uCurrent functionality - not 4-wire, and not necessarily good absolute accuracy, but deltas would be very useful for tracing shorts. Option for audio output, Maybe call  it 'short-finder' rather than resistance.

High voltage (30V) diode test for zeners,  LED strings (e.g. LCD backlights) . cost : A few cents for a crude DC-DC step-up
Maybe extend this to an AC diode test - alternates test polarity at a few Hz and indicates Vf in 2 directions simultaneously. cost : Another few cents for a charge pump inverter off the diode test supply. 

Active overcurrent protection to avoid blowing fuses. (maybe in addition to a real fuse to meet safety specs, but the active cct would trip first).
 
Display : Sharp Memory LCD. High contrast,decent graphics for a nice UI but minimal power draw as no greyscale or colour needed.
E-Ink seems initially attractive but slow update and risk of 'sticking' on a 'safe' reading if something dies could be issues. 
Failing this, a mixed-mode LCD with big segments and a matrix area for UI and secondary readings - this allows a tradeoff between contrast and power draw - you can turn the matrix off when not needed.

Logging  - obviously - this has negligible cost. Maybe to a SD card - shouldn't be hard to design a  safe card slot for when you want to remove the card to dump large logs.

Basic inductance measurement - good enough to identify E12 values.
Capacitance measurement range to cover electrolytics (Fluke I'm talking to you!) and identify excessive ESR

A neat case design to retain probes/cables when not in use. Maybe a compartment to store croc-clips.



 

[mikeselectricstuff]

..and what it should NOT have ..
Colour TFT  - NO NO NO! - too much power draw, you don't need colour on a DMM.
Touchscreen - obviously.
Li-Po battery ( except as an option).
Piss-poor Chinese firmware

[junggwok]

Hi Mike

Saw your post after my comment to the Rigol Handheld multimeter idea. You might have just given Rigol an entirely new business ideas, I wouldn't be surprised in 5 years time someone actually makes something like that. (I mean how hard can it be?)

[mikeselectricstuff]

The basic question when thinking about it is this :
When you put down your DMM and have to reach for another tool - could that tool's functionality ( to the extent you need it) be included in the DMM at minimal cost? In many cases, in my experience, the answer is yes.

Oh, and something else - ability to direct read current using an external shunt - i.e. user-configurable display scaling - no extra cost. Some very obvious indication when this is set - e.g. italic digits or a big icon.

[jucole]

The basic question when thinking about it is this :
When you put down your DMM and have to reach for another tool - could that tool's functionality ( to the extent you need it) be included in the DMM at minimal cost? In many cases, in my experience, the answer is yes.

I'm quite glad you've posted this as it's a project I'm currently working on and there are a couple of good ideas in your post;  but the main struggle for me is nailing that ideal form factor.

[Wytnucls]

I don't think that would fly. Most high-end multimeters are bought by industry for electrical work, where safety is paramount. Fluke cornered that market a long time ago, even in China. No company is going to buy something with a flimsy track record, which could increase litigation and insurance costs.
I would wager that hand-held dmms, designed for electronic work, are part of a niche market. Most labs use bench meters already equipped with the features you mention, albeight at a hefty price.

[mikeselectricstuff]

I don't care about industrial electrics - Fluke, Gossen etc. will always dominate there, and the functionality of current products is fine for them.
I'm specifically thinking about electronics, mostly bench, work, where functionality is more important than being able to put it across a 3-phase 600A busbar without dying.
I think many DMMs compromise their usefulness for elecrtonics by trying to cover too wide a range of functions.
In terms of safety, I'd say the worst case it needs to handle is a worst-case of 240VAC domestic supply, and the DC voltage on a big switchmode PSU reservoir cap.   

I would wager that hand-held dmms, designed for electronic work, are part of a niche market.

Yes, absolutely, but a big niche which IMO is not served well at the moment at the price it could be

I'm quite glad you've posted this as it's a project I'm currently working on and there are a couple of good ideas in your post;  but the main struggle for me is nailing that ideal form factor.

I don't see anything wrong with the existing handheld DMM form-factor (except could be a little smaller) . It's the functionality that has scope for improvement.

[EEVblog]

uCurrent-like low-current performance. Just add a chopper-amp. Not too bothered if accuracy is slightly lower. Anyone who needs to measure current draw to better than 1% can pay extra for that.  Cost : maybe $2

Maybe not that easy.
The protection stuff already in the front end could screw up really low level ranges.
The new uCurrent does 0.05% on the lower ranges and 0.1% on the Amps range, but that doesn't cost a few dollars. Of course you can simply software cal it out cheaply.

A neat case design to retain probes/cables when not in use. Maybe a compartment to store croc-clips.

Now you are into bench-ish meter territory (think Fluke 37), or rather bulky hand-held.

You forgot battery life. Any meter that can't do at least several hundred hours ain't worth a pinch as general use meter.

[EEVblog]

Simultaneous voltage and current measurement (non- isolated with common ground, i.e. same as traditional DMM connectors), with power (simple V*I) display.

I disagree. These already exist and are rather limiting. But better than nothing of course.

The thing I find most limiting about multimeters is that I often have to have more than one at once.
So IMO a really novel meter would have 4 isolated independent inputs. Preferably all dual use, but I'd be happy with dual voltage channels and dual current channels.
Or at least a meter with separate voltage and current channels.
In fact, separate current and voltage channel can be safer because of dedicated probing.
You'd probably have to have them all powered from the one battery though, because you wouldn't want separate batteries to run out and/or leak, but that's not hard to implement.

Brings back some memories:

[mikeselectricstuff]

uCurrent-like low-current performance. Just add a chopper-amp. Not too bothered if accuracy is slightly lower. Anyone who needs to measure current draw to better than 1% can pay extra for that.  Cost : maybe $2

Maybe not that easy.
The protection stuff already in the front end could screw up really low level ranges.
The new uCurrent does 0.05% on the lower ranges and 0.1% on the Amps range, but that doesn't cost a few dollars. Of course you can simply software cal it out cheaply.

It doesn't need to go down as far as uCurrent - something like 0.1uA resolution at a burden of maybe 10R max  would probably be fine. It's more about avoiding the burden than increasing the range of a traditional DMM. Just adding, say, x100 gain would make a big difference.
This is probably the biggest inadequacy in most DMMs for electronics use nowadays.
Most of the time I'm just checking current draw to estimate battery life, find floating pins and check sleep mode is working OK -1% accuracy is more than enough.
Something I'd also like is some integration capability to measure avarage draw of things going itno various sleep mode, but there are some interesting issues there (I looked at this very hard a long time ago).

A neat case design to retain probes/cables when not in use. Maybe a compartment to store croc-clips.

Now you are into bench-ish meter territory (think Fluke 37), or rather bulky hand-held.

yeah - probably - I was thinking more in terms of a detail you can wind the leads round neatly on the outside rather than containing them

You forgot battery life. Any meter that can't do at least several hundred hours ain't worth a pinch as general use meter.

Definitely, but most meters (with segment LCDs) are already OK in this respect - Maybe should have added "battery life no worse than, say. a Fluke 87". Choice of display is probably the biggest issue here. Possibly also a selectable tradeoff between update rate and power draw. Maybe even automatic - reading rate slows when signal static for a while. This is where the Sharp Memory LCD would be a very big win - high res graphics, but contrast and current draw is comparable to a segment display.
Power-to-volume is not too different between alkaline and li-po so It's say stick to 3-4 AA cells, as easier to swap out quickly than recharge a li-po.
However li-po as an option may be useful  (more so if you can charge it via the front terminals!) - if it did have li-po it would absolutely HAVE to be chargeable from USB so you didn't have yet another charger.  For safety use some clever meachanical detail that prevented plugging USB charger in when leads are in input sockets.
Maybe use a standard phone or camera pack so you can do a battery swap. I certainly don't like the idea of a fixed internal battery.
Probably the optimum would be a battery compartment that could take AAs or a standard lipo pack.

Something that's probably at least as important as lifetime is a battery level indicator that says more than just "low" - knowing how long you have left is much more useful than a bit more life. This is something the current market is woefully inadequate at - FFS there's a 4+digit ADC in the box and all you can tell me is "Low" - pretty pathetic.

 

[mikeselectricstuff]

Simultaneous voltage and current measurement (non- isolated with common ground, i.e. same as traditional DMM connectors), with power (simple V*I) display.

I disagree. These already exist and are rather limiting. But better than nothing of course.

Not very common, and a LOT better than nothing for minimal extra build cost.
I'm trying to focus on what could be done in a traditional DMM format at minimal extra cost.
As soon as you add more inputs it adds significantly to cost, size, protection, isolation issues etc.
A commoned V/I input is fine for a large range of applications, and if doing this doesn't add too much cost, you can afford two of them for things like DC/DC efficiency testing  .
The icing on the cake would be if they could talk to each other over bluetooth to give an efficiency reading!
 

[EEVblog]

Probably the optimum would be a battery compartment that could take AAs or a standard lipo pack.

If it already has several hundred hours battery life, then there is no need for any rechargeable solution.
BTW, the Agilent meters used to have charging via the sockets.

Something that's probably at least as important as lifetime is a battery level indicator that says more than just "low" - knowing how long you have left is much more useful than a bit more life. This is something the current market is woefully inadequate at - FFS there's a 4+digit ADC in the box and all you can tell me is "Low" - pretty pathetic.

Yes, almost some meters give you approximate life left when the meter shows "low".
But once again, if it has several hundred hours life anyway, then generally it will always have enough life left for one last job.
Accurate estimate might be handy for long term data logging though.
Also, you want full confidence in all measurements when it shows low. It should either measure accurate or not switch on at all.

[firewalker]

Could it be implemented by a small team of experienced users and not a company? Or the cost would go beyond the target? Crowd funded?

Alexander.

[mikeselectricstuff]

Probably the optimum would be a battery compartment that could take AAs or a standard lipo pack.

If it already has several hundred hours battery life, then there is no need for any rechargeable solution.
BTW, the Agilent meters used to have charging via the sockets.

Yes - probably right.
 

Something that's probably at least as important as lifetime is a battery level indicator that says more than just "low" - knowing how long you have left is much more useful than a bit more life. This is something the current market is woefully inadequate at - FFS there's a 4+digit ADC in the box and all you can tell me is "Low" - pretty pathetic.

Yes, almost some meters give you approximate life left when the meter shows "low".
But once again, if it has several hundred hours life anyway, then generally it will always have enough life left for one last job.
Accurate estimate might be handy for long term data logging though.
Also, you want full confidence in all measurements when it shows low. It should either measure accurate or not switch on at all.

The big problem with "low" is you tend to just ignore it until it's too late! A few more states would help a lot. "Make sure you have a battery in stock", "Change battery when convenient", "Change battery NOW, but I'm disabling the backlight and slowing down to squeeze a bit more out" and "Game Over".

[jucole]

It's the functionality that has scope for improvement.

I totally agree!    Some of the ideas I was toying around with was inductive base-pad re-charging like a toothbrush; maybe I hang it onto the wall when I've finished for the day and it's all charged for the next day.  2 input jacks per channel for measurements (so I don't have to keep switching jack sockets).   Adding speech - so I don't short stuff whilst looking trying to look at the display;  and one of the really crazy ideas was the ability to upload repair/diagnostic scripts to it via the Bluetooth.

I did manage to blag some very new interesting DMM chipsets from one of the big players using a  A-Team Templeton "Faceman" Peck routine but I'll probably be using off-the-shelf uC / FPGA stuff for this concept project.

[amyk]

Maybe use a standard phone or camera pack so you can do a battery swap. I certainly don't like the idea of a fixed internal battery.
Probably the optimum would be a battery compartment that could take AAs or a standard lipo pack.

This would be an example of the type of feature that a Chinese company is far more likely to come out with --- instead of the "let's force you to use our very expensive proprietary battery pack" it's more along the lines of "use what's already available" that their thinking tends along. Although for various reasons, I don't think Rigol is this type of company; this sort of versatility is founded in the  shanzhai culture.

[mikeselectricstuff]

Could it be implemented by a small team of experienced users and not a company? Or the cost would go beyond the target? Crowd funded?

Alexander.

Maybe. A (very) few people to spec and do design, then crowdfund for volume part pricing and case mould tooling. The case quality would have to be comparable to current mid-range models.
Most of the individual enhancements are not really that hard.

Oh, and of course it should start up absolutely instantly (No embedded OS or flabby firmware please!) Open source firmware would be nice. Not so bothered about hardware as long as schematics are available.

[Marco]

Simultaneous voltage and current measurement (non- isolated with common ground, i.e. same as traditional DMM connectors), with power (simple V*I) display. Cost : this is basically the addition of a multiplexer.  Don't mind if reading rate is a little slower in this mode.

This is just going to go wrong far too often, I'd want separate grounds, use a high side current sensing IC to measure the current or two isolated analogue sections.

uCurrent-like low-current performance. Just add a chopper-amp. Not too bothered if accuracy is slightly lower. Anyone who needs to measure current draw to better than 1% can pay extra for that.  Cost : maybe $2

Just make sure you need to take extra steps to activate the mode, since input protection is going to be minimal in this mode ... I'd hate to just put it in by accident and fry everything.

Very low resistance mode, using uCurrent functionality - not 4-wire, and not necessarily good absolute accuracy, but deltas would be very useful for tracing shorts. Option for audio output, Maybe call  it 'short-finder' rather than resistance.

Why not 4 wire?

How do you want to do the active current cut out? AFAICS only relays will have low enough resistance over rated input voltage, high voltage MOSFETs will add too much burden. Can the relay be turned off fast enough?

[mikeselectricstuff]

It's the functionality that has scope for improvement.

I totally agree!    Some of the ideas I was toying around with was inductive base-pad re-charging like a toothbrush; maybe I hang it onto the wall when I've finished for the day and it's all charged for the next day.  2 input jacks per channel for measurements (so I don't have to keep switching jack sockets). 

Single socket adds complication ( and precludes dual V/I measurement). I think most people accept having to swap for I measurement. Also has some safety advantages. Maybe a change I'd make would be a single 10A socket and amplifier for mA/uA instead of a second current socket.

 Adding speech - so I don't short stuff whilst looking trying to look at the display;  and one of the really crazy ideas was the ability to upload repair/diagnostic scripts to it via the Bluetooth.

Speech could be less silly than it sounds, and also minimal cost to implement. You'd be looking at low-en ARM to support a graphic display, so it ought to be able to do speech all in software - not a problem if the display freezes when speaking. if it has Bluetooth you could do BT audio to an earpiece. You'd definitely want some flexibility in adjusting speed and content though. (Make your DMM talk like Dave!  )

but I'll probably be using off-the-shelf uC / FPGA stuff for this concept project.

can't think why you'd need FPGA or even CPLD for this.

[mikeselectricstuff]

Simultaneous voltage and current measurement (non- isolated with common ground, i.e. same as traditional DMM connectors), with power (simple V*I) display. Cost : this is basically the addition of a multiplexer.  Don't mind if reading rate is a little slower in this mode.

This is just going to go wrong far too often, I'd want separate grounds, use a high side current sensing IC to measure the current.

Totally disagree. Most of the time you want to know V and I of the same source. Seperating adds significant cost.

uCurrent-like low-current performance. Just add a chopper-amp. Not too bothered if accuracy is slightly lower. Anyone who needs to measure current draw to better than 1% can pay extra for that.  Cost : maybe $2

Just make sure you need to take extra steps to activate the mode, since input protection is going to be minimal in this mode.

No. It would use teh existing shunt, just with some gain. Protection no different

Very low resistance mode, using uCurrent functionality - not 4-wire, and not necessarily good absolute accuracy, but deltas would be very useful for tracing shorts. Option for audio output, Maybe call  it 'short-finder' rather than resistance.

Why not 4 wire?

Extra cost. I'm specifically thinking about functionality for finding shorts on PCB - delta and audio will add a lot of function at minimal cost,. especially as you could re-use the current amplifier.

Remember I'm focussing on how a normal mid-range DMM can be made more useful, not trying to design a high-end bells-and-whistles thing.
 

[EEVblog]

The big problem with "low" is you tend to just ignore it until it's too late! A few more states would help a lot. "Make sure you have a battery in stock", "Change battery when convenient", "Change battery NOW, but I'm disabling the backlight and slowing down to squeeze a bit more out" and "Game Over".

Agreed.
Big scrolling text as last resort - "Change the F'ING battery you moron!"

[EEVblog]

Could it be implemented by a small team of experienced users and not a company?

Yes. Although if you were really serious and wanted to go into a production and be a serious player, you'd try and team up with an existing meter OEM in some way I suspect.
These things work better as a dictatorship though. There have been a few big threads on DIY community meters, and it always ends up compromise and never happens because of having too many cooks.

Or the cost would go beyond the target? Crowd funded?

If you wanted to produce a real production market ready product with custom injection molded case and range switches, battery compartment and all the bells and whistles then it could easily go over budget and fail. More likely than not I'd say.
I wouldn't want to do it that way, I'd prefer a more off-the-shelf type DIY looking approach.

[jucole]

but I'll probably be using off-the-shelf uC / FPGA stuff for this concept project.

can't think why you'd need FPGA or even CPLD for this.

It's got quite a few more features that will need an FPGA which I only really added because I wanted to learn FPGAs.

[firewalker]

No. Not a community thing. I would die instantly. And no open source/hardware as requirement. I was thinkig a group of 5 as a max.

I would also like a settable voltage level pass/fail beep.

Alexander.

[peter.mitchell]

one big feature - alert the user on the display that the fuse is blown when the fuse is blown instead of reading 0.000, a lot of meters do this but there are significantly more that don't.
important normal features like jack sensing - continuous beep when plug is in amps jack on volts measurement ect, same as above, lots do, lots also don't.
in the continuity measurement/beeper, have a 2 stage beeper, high and low freq, say... less than 50 ohms low freq, less than 5 ohms, higher freq.
some sort of adjustable sample averaging, so adjustable resolution vs speed.
i'd consider removing the rotary switch, possibly free up some front panel and internal space, i wish there was a nice way to be able to have the meter "saved" in a mode, so when you turn it on/off/on it is still in the same mode - this also fixes the issue of default turn on mode.
i'm sure inductor measurement could be done fairly simply, i do agree basic ballpark inductance would be an excellent addition to most multimeters.
weight isn't really an issue, size is only somewhat of an issue too, i mean, there is a fairly large range of acceptable sizes of multimeter.
i think AAs are the way to go though, i'd be fine with even a ridiculous number of them too, say 8, simply because they're common and relatively energy dense and cheap, also, if you have 8 AAs in series, you cut down on the boost converters for backlights, diode tests, amplification ect



I do agree though, community would kill progress on something like this. Compromises are fine, provided you're compromising the right things.

[kripton2035]

nice project !
but keep it the DIY way
if you go kickstarter or something, you will have surely a wall of patents in front of you !

[FrankBuss]

These things work better as a dictatorship though. There have been a few big threads on DIY community meters, and it always ends up compromise and never happens because of having too many cooks.

I think there is no best multimeter. Even a dictatorship could only create a multimeter which fits the needs of a minority and which is a compromise. Some people might need a fancy display, some people might prefer a bluetooth connection and a smart phone application, 1, 2 or 4 independent/common ground channels etc., all with different impact on battery life time, case design etc.

What about a modular approach? I think we could agree that the basic requirement is to measure voltage, current and resistance. So a good start would be to design such a module, including input protections and with a digital interface. I guess it could be the same module for all three measurements. For current measurements it needs just an extra shunt and for resistance measurement it needs just an extra current limited and protected adjustable voltage source, which could be used for the zener diode test, too. It could communicate over SPI to a main CPU.

This module could be like a lego block to build your personal multimeter. People who want it isolated can easily add some optocouplers and an isolated DC/DC converter. If you need 5 channels, just build 5 of these modules.

The firmware has to reflect this flexibility. Would be nice to have a C++ library, which does the measurement, all needed calibrations, auto-range etc. You could run this library on your iPhone and then you need only a dumb bluetooth/SPI translator on the multimeter side (with a device identification or a local EEPROM to store the calibration data), or you could run it on the PC over USB, or on a more powerful microcontroller with a graphics display on the multimeter itself. It could be even connected to an Arduino, which would make it easier for anyone to use it how you like it. You could write your own sketch to implement your special kind of upper/lower limit test for manufacturing in a matter of minutes, with logging, beeping and smart-phone connection.

[jucole]

What about a modular approach? I think we could agree that the basic requirement is to measure voltage, current and resistance. So a good start would be to design such a module, including input protections and with a digital interface. I guess it could be the same module for all three measurements. For current measurements it needs just an extra shunt and for resistance measurement it needs just an extra current limited and protected adjustable voltage source, which could be used for the zener diode test, too. It could communicate over SPI to a main CPU.

I agree with the module approach;  In my system each channel module would register it's capabilities to the main CPU on startup, then the main CPU simply adds a system menu option item for it in the UI and displays the actual measurement information when required to do so;  that way the unit would potentially readily accept high-end modules or low-end ones.

[elgonzo]

I think there is no best multimeter. Even a dictatorship could only create a multimeter which fits the needs of a minority and which is a compromise.

Certainly right. But at least a DMM designed by "dictatorship" principle has a fair chance to cater to a certain user group extremely well. Products designed by committee are often jacks of all trades, masters of none, and it usually takes a quite an amount of time before that committee can actually make a decision...

[elgonzo]

What about a modular approach? I think we could agree that the basic requirement is to measure voltage, current and resistance. So a good start would be to design such a module, including input protections and with a digital interface.

That is an idea i like. Connect the DMM circuitry to the digital control circuitry through a daisy-chainable interface such as SPI/I2C or alike. That way, you can easily add/duplicate modules without changing the existing circuitry.
(EDIT: If the MCU has enough I/O pins, you would not even need a dedicated serial bus for that purpose...)

The good thing about this is, since the modularity functionality can be handled entirely in firmware, you don't need to spend much effort in the early stages of firmware development on this -- just make the thing run with the single given module. Add modularity functions later to the firmware. You don't need "committee design" to get the DMM done...

"Bad" thing about this is, you (EDIT: the one who wants to build a multi-module DMM) have to think ahead in terms of size/resolution your display will need for the expected functionality, and how much memory your MCU will need to accommodate it -- which might or might not be cost drivers...

[FrankBuss]

So the first step would be to design one channel with all the requirements Mike listed in his first post. If Dave and the other analog experts in this forum help designing the analog side, this could be a very useful module for many applications, even if the multimeter itself ends like the other discussions about DIY multimeters in this forum

The resolution depends on the quality of the parts, e.g. a low noise op-amp and 24 bit ADC for the high-end version, and a standard op-amp with a 16 bit ADC for the low-cost version. The ADC is easy to replace, there are really nice pin compatible chips from Analog Devices with the same interface for both resolutions. But would be more difficult for the op-amp and the rest of the analog frontend, and might even need a more complex circuit for better resolution, not just better parts.

[Marco]

Active overcurrent protection to avoid blowing fuses. (maybe in addition to a real fuse to meet safety specs, but the active cct would trip first).

How do you want to do this cheaply? Lets say you want protection for mains at 10A and you want ~50 mOhm, already uncomfortably high, you're already looking at a 10$ MOSFET. I said relays before, but I failed to consider those generally don't have good DC breaking capacity.

[echen1024]

I'm beginning to think this design will need a large-ish dot matrix display. We could have let's say, 5 channels, so we could do 4 wire resistance, and possibly voltage at the same tine. Otherwise, these channels would have 2 for current, another 2 for voltage, and maybe the last one for a LCR meter. While this might be a bit too complicated, this possibly just turned into the most versatile multimeters I can think of.

[mikeselectricstuff]

one big feature - alert the user on the display that the fuse is blown when the fuse is blown instead of reading 0.000, a lot of meters do this but there are significantly more that don't.

Absolutely, but an active overcurrent protector would make this less necessary.

in the continuity measurement/beeper, have a 2 stage beeper, high and low freq, say... less than 50 ohms low freq, less than 5 ohms, higher freq.

As mentioned above, but has to be user-configurable. In fact if you implemented a pass/fail limit function, the continuity could just be a special case of that.

some sort of adjustable sample averaging, so adjustable resolution vs speed.

Maybe, but not sure how useful that would be.

i'd consider removing the rotary switch, possibly free up some front panel and internal space, i wish there was a nice way to be able to have the meter "saved" in a mode, so when you turn it on/off/on it is still in the same mode - this also fixes the issue of default turn on mode.

Maybe, Unlike twiddly knobs on scopes, I don't think (decent) buttons would be much worse than a rotary switch on a DMM, though may add expense for signal switching. May help reduce tooling costs though, but rotary does have the familiarity. Maybe buttons in a circle..!
 

i'm sure inductor measurement could be done fairly simply, i do agree basic ballpark inductance would be an excellent addition to most multimeters.

Especially with SMD inductors - I'd suggest 100mH down to whatever is feasible at low cost - 1uH resolution would be good, and would cover the majority of things like SMPS inductors.

weight isn't really an issue, size is only somewhat of an issue too, i mean, there is a fairly large range of acceptable sizes of multimeter.

Shouldn't be bigger or heavier than a conventional DMM

i think AAs are the way to go though, i'd be fine with even a ridiculous number of them too, say 8, simply because they're common and relatively energy dense and cheap, also, if you have 8 AAs in series, you cut down on the boost converters for backlights, diode tests, amplification ect

In terms of size and weight I'd say 4xAA would be a maximum. It should be possible to get decent battery life with that. Apart from HV diode test (which can be turned on only when needed) , you probably don't need any higher voltages than 6V - with a high contrast LCD, power for backlighting is very low as it's only needed when too dark to read - maybe 4 white LEDs at 5-10mA each max.

I do agree though, community would kill progress on something like this. Compromises are fine, provided you're compromising the right things.

Probably, though there's nothing wrong with asking for ideas - there are bound to be some good ones, and you can ignore the rest.

[mikeselectricstuff]

The big problem with "low" is you tend to just ignore it until it's too late! A few more states would help a lot. "Make sure you have a battery in stock", "Change battery when convenient", "Change battery NOW, but I'm disabling the backlight and slowing down to squeeze a bit more out" and "Game Over".

Agreed.
Big scrolling text as last resort - "Change the F'ING battery you moron!"

..and if it has speech, even more possibilities!

[mikeselectricstuff]

Active overcurrent protection to avoid blowing fuses. (maybe in addition to a real fuse to meet safety specs, but the active cct would trip first).

How do you want to do this cheaply? Lets say you want protection for mains at 10A and you want ~50 mOhm, already uncomfortably high, you're already looking at a 10$ MOSFET. I said relays before, but I failed to consider those generally don't have good DC breaking capacity.

Not given it much thought - I think you'd need to compromise and accept that at high voltage, a fuse will blow, but to avoid acccidents at low voltages, there may be scope for something useful, e.g. MOSFET switch with a TVS or zener across it to deal with HV situations. 
However the idea of simplifying current to use a single shunt with amplification for lower ranges may reduce nuisance blowing of lower-range fuses, making any clever protection much less necessary anyway.

[mikeselectricstuff]

If you wanted to produce a real production market ready product with custom injection molded case and range switches, battery compartment and all the bells and whistles then it could easily go over budget and fail. More likely than not I'd say.
I wouldn't want to do it that way, I'd prefer a more off-the-shelf type DIY looking approach.

There are probably enough off-the-shelf cases that you could  find something suitable, at least for a Mark I to establish if there's enough demand to fund a mould, while still looking fairly professional.
Rotary switch is probably the biggest issue, but going to buttons may be a good compromise to deal with that, as long as there are enough buttons for 1-touch to main functions. Obviously there would be a row of function keys under the display
 

[mikeselectricstuff]

The big problem with "low" is you tend to just ignore it until it's too late! A few more states would help a lot. "Make sure you have a battery in stock", "Change battery when convenient", "Change battery NOW, but I'm disabling the backlight and slowing down to squeeze a bit more out" and "Game Over".

Agreed.
Big scrolling text as last resort - "Change the F'ING battery you moron!"

..or maybe the display digits get smaller and smaller and smaller

[elgonzo]

I'm beginning to think this design will need a large-ish dot matrix display. We could have let's say, 5 channels, so we could do 4 wire resistance, and possibly voltage at the same tine. Otherwise, these channels would have 2 for current, another 2 for voltage, and maybe the last one for a LCR meter.

If you speak about circuit design, don't worry too much about the display. Display series often share the same electrical interface/protocol amongst the models of different size and resolution.

Nothing speaks against having a normal-ish display in case you don't want to build a DMM with many channels.
If you want more channels, just use a larger display model. But that's not the real issue. The problem is that somebody has to do the firmware for this configuration.

While this might be a bit too complicated, this possibly just turned into the most versatile multimeters I can think of.

Instant death!
Please insert coin to continue. 

[mikeselectricstuff]

What about a modular approach? I think we could agree that the basic requirement is to measure voltage, current and resistance. So a good start would be to design such a module, including input protections and with a digital interface. I guess it could be the same module for all three measurements. For current measurements it needs just an extra shunt and for resistance measurement it needs just an extra current limited and protected adjustable voltage source, which could be used for the zener diode test, too. It could communicate over SPI to a main CPU.

I agree with the module approach;  In my system each channel module would register it's capabilities to the main CPU on startup, then the main CPU simply adds a system menu option item for it in the UI and displays the actual measurement information when required to do so;  that way the unit would potentially readily accept high-end modules or low-end ones.

Too complex - all sorts of issues with interconnect, holes in the case. I'm sure a modular system would suit some people, but most people are happy with the basic DMM format. I'm just seeing how it could be improved within its present format and price range. The only modular stuff I'd see making sense are add-ons to the core functionality, like Bluetooth or maybe Wifi (not both), speech perhaps.

[mikeselectricstuff]

but I'll probably be using off-the-shelf uC / FPGA stuff for this concept project.

can't think why you'd need FPGA or even CPLD for this.

It's got quite a few more features that will need an FPGA which I only really added because I wanted to learn FPGAs.

..there goes your battery life!

[elgonzo]

The big problem with "low" is you tend to just ignore it until it's too late! A few more states would help a lot. "Make sure you have a battery in stock", "Change battery when convenient", "Change battery NOW, but I'm disabling the backlight and slowing down to squeeze a bit more out" and "Game Over".

Agreed.
Big scrolling text as last resort - "Change the F'ING battery you moron!"

..or maybe the display digits get smaller and smaller and smaller

But... every serious electronics engineer has a Mantis

[mikeselectricstuff]

Yes. Although if you were really serious and wanted to go into a production and be a serious player, you'd try and team up with an existing meter OEM in some way I suspect.

..except I think a lot of the problem with the existing market is companies are used to having a big product range to cover a broad market, and charging more for options that cost little to implement.
 I think a new player with a completely clean slate approach, to put as much functionality in for the specific niche of electronics work, and ignoring the heavy industrial market, could potentially produce something very nice just by making a few relatively small enhancements and specialisations to the current DMM format, and using newer technology, particularly in the display area.
Once you have code space and power for significantly more (easily upgradeable) software, and a high-res display with minimal impact on battery life you have a lot of potential which I can't see anyone addressing at the moment.

[Lightages]

I agree with most of your points Mike. As you have pointed out most of them require minimal additional parts.

To do simultaneous current and voltage is already such a no brainer I don't know why it isn't being done. My UT71E does this, but for AC only. It seems a rather silly oversight that they made it do AC only.

Why not 4 wire for additional resistance modes? Most multimeters have 4 input jacks. Just because one of them is dedicated to be a common doesn't mean it has to be this way. When switching between different functions the jacks could also be reconfigured. My Brymen BM869 and BM525 both have made dual use of the four jacks. Dual temperature mode uses the mA and A sockets as the second input for the thermocouple. If this can be done a four wire setup then for low resistance measurement is also very possible.

The four jacks might also be able to be reconfigured for use as two independent inputs for independent voltage and current measurements but I suspect this would get rather involved mechanically with switching and therefore would raise the additional costs too much.

Again, dual use could be made of the mA and A jacks to be used as independent inputs for a uCurrent like functionality just like they are used for the dual temperature function on the Brymens.

Built in Bluetooth would add very little to the cost and possible could eliminate any need for a removable memory car to transfer logging data.

My other peeves and ideas about multimeters...

Let me select to never have the back light turn off if I want.

Don't force me to listen to beeps I don't want, ie I don't need to hear a beep because I changed a function. Make every sound selectable.

Why not a variable tone for resistance?

A simple transformer couple power input jack would make some logging meters much more practical. It isn't hard to make a properly isolated AC power input jack so some low power wall wart transformer could be used for indefinite power. It only needs to supply a few milliwatts so a big isolation could be provided without worrying about efficiency.

Logic probe function is also a no brainer. Make it flash a symbol on the display and/or make tones based on logic levels.

Stick a simple optically isolated mini USB jack on all multimeters! This might be simpler and cheaper to do than all the extra considerations made during design and manufacture for the IR ports and attachment points for the optical interfaces. If I am wrong, then just include the damn cable or stop charging ridiculous prices for a such a simple thing.

Many of the things discussed and some that have not been are software things. They could be done with no real problems with extra costs and re-tooling.

[MasterOfNone]

Why not remove the Selector Knob, and then remove all the buttons (except the power button) and remove the display! That’s right no display and no way to select the type of measurement (on the device).
So now we would have a box with just a power button and connections for the probes.
Now you could try to convince engineers that to use the DMM they need to develop psychic powers only available to highly skilled individuals, but with engineers you probably wouldn’t have very much luck with that. So a better option would be to provide apps for phones, tablets and PC’s that can display the readings from one or more DMM using Bluetooth.  The app would also allow you to select the function being performed by each DMM module.

I know, I know, that has got to be the worst idea you’ve seen on this forum ever, but I knew I could get Touch screens and Colour displays back into this thread somehow.   

[mikeselectricstuff]

Why not 4 wire for additional resistance modes?

I just don't think it's necessary often enough to justify any additional cost

The four jacks might also be able to be reconfigured for use as two independent inputs for independent voltage and current measurements but I suspect this would get rather involved mechanically with switching and therefore would raise the additional costs too much.

As soon as you seperate them you need data and power isolation, which adds cost and complexity

Built in Bluetooth would add very little to the cost and possible could eliminate any need for a removable memory car to transfer logging data.

Yes - if only to allow easy firmware upgrades, BT as standard could probably justify the cost.

My other peeves and ideas about multimeters...

Let me select to never have the back light turn off if I want.

User specified timeout. or maybe better a light sensor to make it mostly automatic

Don't force me to listen to beeps I don't want, ie I don't need to hear a beep because I changed a function. Make every sound selectable.

Fine. Again no cost.

Why not a variable tone for resistance?

Why not a variable tone for every function? Combine with delta mode for nulling without looking.
2-tone continuity could just be a special case of this

A simple transformer couple power input jack would make some logging meters much more practical. It isn't hard to make a properly isolated AC power input jack so some low power wall wart transformer could be used for indefinite power. It only needs to supply a few milliwatts so a big isolation could be provided without worrying about efficiency.

No - you should be able to make power draw low enough for logging. Unnecessary cost.

Logic probe function is also a no brainer. Make it flash a symbol on the display and/or make tones based on logic levels.

again, this can be a special case of configurable, variable tones.
..and while on the subject of variable tones, and audio equivalent to a bargraph display could be a good way to indicate changes happenning faster than the display - the ear is good at discerning patterns

Stick a simple optically isolated mini USB jack on all multimeters!

No need if you have Bluetooth.

[FrankBuss]

Why not 4 wire for additional resistance modes?

I just don't think it's necessary often enough to justify any additional cost

I just needed this feature of my HM8018 to check which side of a 0.04 ohm resistor was on the same net at a far away point in a soldered multilayer PCB. But if such a resolution is possible with a good delta measurement implementation, it would be sufficient.

[elgonzo]

Stick a simple optically isolated mini USB jack on all multimeters!

No need if you have Bluetooth.

Yes, and no need for cabling -- i have so many USB cables connected to my PC, you might think it is an old telephone switch... 

[ConnorGames]

Stick a simple optically isolated mini USB jack on all multimeters!

No need if you have Bluetooth.

Yes, and no need for cabling -- i have so many USB cables connected to my PC, you might think it is an old telephone switch... 

Except that you now need a bluetooth adapter. None of my PC's have Bluetooth, and I suspect I am not alone. This makes USB a LOT more convenient!

[BravoV]

Except that you now need a bluetooth adapter. None of my PC's have Bluetooth, and I suspect I am not alone. This makes USB a LOT more convenient!

C'mon, they're dirt cheap, I mean really cheap, just buy a dozen of these, bring them back home and start plug in each at every PC you can find. 

[echen1024]

I actually like the modular approach. We have a standard interface, say, I2C, and have plugin mofules that can do a wide variety of things, such as uCurrent like functionality, LCR meter, and maybe even like the agilent u1253b, a programmable function gen. Just a 5 MHz simple thing, nothing to complex.

[Dark Prognosis]

..and what it should NOT have ..
Colour TFT  - NO NO NO! - too much power draw, you don't need colour on a DMM.
Touchscreen - obviously.
Li-Po battery ( except as an option).
Piss-poor Chinese firmware

I could do without the touch screen myself because if that meant 50 dollars more or have without I would do without (I don't like touching my screens with anything as they will wear out and get filthy out in the field).

One thing I absolutely want that I had on an old Radio Shack DMM back in 1985 that I haven't found on modern DMMs that cost around the same (was $19.95 back then) is a zero button.  WTF?!?  No damn way to zero out the wires/probes except using your head and remembering your probes cause 0.9 ohms of resistance.  Why they dropped this feature I don't know.

If Rigol makes one I expect it to be around 50 dollars max or no dice.

[geostep]

Except that you now need a bluetooth adapter. None of my PC's have Bluetooth, and I suspect I am not alone. This makes USB a LOT more convenient!

Don't overlook the fact that the USB cable could power the meter as well, extending the life of the internal batteries.
USB could also charge the internal batteries but that demands a rechargeable battery technology.  Hmmm, maybe a supercap as an internal power source?

- George

[SArepairman]

I think that if its for general electronics use then maybe it could have some pins on the back so you can hook up a bunch of low voltage measurements.

Kind of like having a few extra centek meters in one package, like 20V max, 0.1v resolution, and have it display. It might be useful if you can just hook it up and know "oh shit the current just shot up by 200mA"

Just so you can have an over view of whats going on in the whole system while you make more precise measurements...

Or just have a port on the back where you can stack some "optional" matchbox sized multimeters and have the ability to display like 6 channels on your main screen if you wanted to, just for situational awareness

[Monkeh]

One thing I absolutely want that I had on an old Radio Shack DMM back in 1985 that I haven't found on modern DMMs that cost around the same (was $19.95 back then) is a zero button.  WTF?!?  No damn way to zero out the wires/probes except using your head and remembering your probes cause 0.9 ohms of resistance.  Why they dropped this feature I don't know.

http://www.ebay.com/itm/221270085516

[FrankBuss]

Hmmm, maybe a supercap as an internal power source?

This won't work. Even a 100F supercap for 10 EUR stores only 1% energy of a typical AA battery (see this link). Digikey has a 1,000F supercap, but it costs 104 EUR and is 10x4cm. Let's talk again about supercaps when they've created something cheaper, smaller and better with nanotubes.

[Paul Moir]

Something that beeps when the measured reading varies by more than x% of the current reading would be a killer for field apps.

I don't care about industrial electrics - Fluke, Gossen etc. will always dominate there, and the functionality of current products is fine for them.

From where I stand, the industrial market is much more flexible than you think.  We just need CAT such and such and features the guys want.

[Dark Prognosis]

One thing I absolutely want that I had on an old Radio Shack DMM back in 1985 that I haven't found on modern DMMs that cost around the same (was $19.95 back then) is a zero button.  WTF?!?  No damn way to zero out the wires/probes except using your head and remembering your probes cause 0.9 ohms of resistance.  Why they dropped this feature I don't know.

http://www.ebay.com/itm/221270085516

Where is the zero button at as I stated that is what I wanted like I had back in 1985.  WTF, this is 2013 and the button is gone and it can say auto ranging all it wants but that button is very handy to have.

[Lightages]

I think you are missing the point. Many multimeters have this "zero" button but is now called "REL" for relative or a triangle for delta. This is the same function that you lament.

[neggles]

Where is the zero button at as I stated that is what I wanted like I had back in 1985.  WTF, this is 2013 and the button is gone and it can say auto ranging all it wants but that button is very handy to have.

As Lightages said, it's called Relative or Delta now. Quite useful to compare resistance of a batch of resistors for example.

I'd just like to propose NOT including stupid superfluous features like the Agilent U1232A's "flashlight" (which seems fairly pointless, given its location on the BACK of the meter and high power draw) and also pose a question

This is the back of said Agilent:


Why on earth does it have those stupid clips for the test probes. Does anyone (in electronics, mind you) ever actually use those? I've never had any cause to in my life, all they seem to do is add thickness to the device for next to no reason. The likelihood of finding that you need to probe something that happens to be exactly that distance apart seems almost zero to me. Very irritating, fortunately my $50 meter has them in its rubber outer shell so they were relatively easy to cut off.

[andtfoot]

Why on earth does it have those stupid clips for the test probes. Does anyone (in electronics, mind you) ever actually use those?

I do... I clip the probes in there for storage to prevent the ends being munted in transportation. Like this:


Edit: I only just noticed the 'in electronics' caveat. I guess in a lab environment they don't do much, but then does the extra space actually matter?

[BravoV]

Why on earth does it have those stupid clips for the test probes. Does anyone (in electronics, mind you) ever actually use those?

I do, like protecting those sharp tips it self from getting blunt, and also the pouch from getting "stabbed". 

[neggles]

I do, like protecting those sharp tips it self from getting blunt, and also the pouch itself too from getting "stabbed". 
<image snip>

I do... I clip the probes in there for storage to prevent the ends being munted in transportation. Like this:
<image snip>
Edit: I only just noticed the 'in electronics' caveat. I guess in a lab environment they don't do much, but then does the extra space actually matter?

That's a fine point. I dislike wrapping wires around the sides of my meter, though, so I tend to wrap them lengthways and secure with a rubber band.

And then BravoV goes ahead and shows exactly that done... your meter even has little slots for the finger guards...

Okey dokey folks, I stand corrected, they are indeed a good idea (if they actually work to retain the probes, mind you - I guess I need a better meter!)

And hey,  I didn't mean "For lab use" - if we're in a lab here then you might even be using a bench DMM - I often use my DMM outside of a lab (while working on something on-location). I merely meant to exclude uses that might be exclusive to electricians' work rather than electronics work.

[BravoV]

That's a fine point. I dislike wrapping wires around the sides of my meter, though, so I tend to wrap them lengthways and secure with a rubber band.

I do that with in mind that wrapping the cables the length ways spun at the meter will not experience sharp bend, and also much less mechanical stress on the cables especially at those fine copper strands inside them.

Also the spun wires across length way will act as bumper to the meter against mild mechanical impact, especially at the front plastic window, dented or worst cracked display window is not fun. 

..... (if they actually work to retain the probes, mind you - I guess I need a better meter!)

Not sure about cheapy, those clips hold the probes quite snugly and they won't detach easily by it self.

[Dark Prognosis]

I think you are missing the point. Many multimeters have this "zero" button but is now called "REL" for relative or a triangle for delta. This is the same function that you lament.

REL?  How does that even work?  With the zero function you touch the wires together (the wires may not just be the probes) and hit zero so it removes the internal resistances.

How does REL actually work?

[mikeselectricstuff]

Why on earth does it have those stupid clips for the test probes. Does anyone (in electronics, mind you) ever actually use those?

I do... I clip the probes in there for storage to prevent the ends being munted in transportation. Like this:


Edit: I only just noticed the 'in electronics' caveat. I guess in a lab environment they don't do much, but then does the extra space actually matter?

These clips can also be useful for handheld field use - you can clip the probe further up , so you have a probe in one hand and probe+dmm in the other

[mikeselectricstuff]

..and what it should NOT have ..
Colour TFT  - NO NO NO! - too much power draw, you don't need colour on a DMM.
Touchscreen - obviously.
Li-Po battery ( except as an option).
Piss-poor Chinese firmware

I could do without the touch screen myself because if that meant 50 dollars more or have without I would do without (I don't like touching my screens with anything as they will wear out and get filthy out in the field).

A touchscreen would probably be just about acceptable as long as it wasn't a fragile plasticky type and was sufficiently robust and didn't affect screen contrast.
There are some areas where touchscreens are totally inappropriate, like automotive and TV remotes, as they force you to look at the screen instead of feeling for a knob/button without looking. This is probably not a major issue for a DMM, but I don't think a DMM  UI would need enough buttons for a touchscreen to add enough benefit to jusutify the downsides. Somewhere a TS really scores is when you occasionally need full alphanumeric entry, or selection from a large number of options, which is unlikely to be the case for the scale of DMM I'm talking about, which worst-case may need a numeric entry for limit values.

[Dark Prognosis]

Most of the DMMs I have used I set it and forget it and get into all sorts of cramped positions to get a reading while breaking my neck (well, not really but it sure feels like it) to see what the reading is.  Having a screen needing to be touched thousands of times the screen will eventually show rub marks and it gets hard to see what is under the rub mark, or what is supposed to be under it.  It is like those touch screen at the self checkout in the grocery stores because you honestly can't see what is under them and those things are built for an industrial environment POS type setup.

[kripton2035]

better a nice contrasted display and a rotary encoder than a touchscreen yes.

[Dark Prognosis]

better a nice contrasted display and a rotary encoder than a touchscreen yes.

Exactly.

[danb35]

How does REL actually work?

I'm sure it depends on the meter.  On my Fluke, you can hit it at any time, with any reading, and that reading becomes 0.  Any subsequent measurements are relative to that new zero point.  So, to use your case as an example, touch the probes/wires together, get a reading of 0.4 ohms, and hit the REL button--the meter now reads 0.  Any further measurements until you take it out of REL mode will be relative to that 0.4 ohm reading.  As far as I can tell (or find in the manual), this works in any mode--voltage, amps, ohms, etc.

I don't know how common this feature is, but my $30 TekPower meter has it, so it's definitely not confined to high-end DMMs.

[Dark Prognosis]

How does REL actually work?

I'm sure it depends on the meter.  On my Fluke, you can hit it at any time, with any reading, and that reading becomes 0.  Any subsequent measurements are relative to that new zero point.  So, to use your case as an example, touch the probes/wires together, get a reading of 0.4 ohms, and hit the REL button--the meter now reads 0.  Any further measurements until you take it out of REL mode will be relative to that 0.4 ohm reading.  As far as I can tell (or find in the manual), this works in any mode--voltage, amps, ohms, etc.

I don't know how common this feature is, but my $30 TekPower meter has it, so it's definitely not confined to high-end DMMs.

I have not found it in a regular meter around that price.  The one shown to me is the type I do not like but surprised I am to have seen it.

[neggles]

I have not found it in a regular meter around that price.  The one shown to me is the type I do not like but surprised I am to have seen it.

It's in my digi-tech meter that I bought from Jaycar for $40 two years ago. it's even in the $12 Uni-T meter he linked you on eBay before ( http://www.ebay.com/itm/221270085516 - "relative" button ) - so it's not an uncommon feature at all.

It works like danb35 says on every meter i've come across - the only difference from a zero button on older meters is the name.

[EEVblog]

better a nice contrasted display and a rotary encoder than a touchscreen yes.

As much as I like the rotary range switch, it is actually a poor choice. Contact wear out, you have to switch through ranges you don't want to get to the one you do what.
And if it's a DIY project, a complex range switch would suck up half your development time, budget, and sanity I suspect.
I'd just use a nice big rubber membrane keypad.

[Dark Prognosis]

better a nice contrasted display and a rotary encoder than a touchscreen yes.

As much as I like the rotary range switch, it is actually a poor choice. Contact wear out, you have to switch through ranges you don't want to get to the one you do what.
And if it's a DIY project, a complex range switch would suck up half your development time, budget, and sanity I suspect.
I'd just use a nice big rubber membrane keypad.

Hmmmm, I hadn't thought about the rubber since my hands do sweat with the work I do and the rubber would be nice but the digital rotary dial I imagine would be a pain in the ass to implement and probably even worse to dick around with in the field. 

[Dark Prognosis]

I have not found it in a regular meter around that price.  The one shown to me is the type I do not like but surprised I am to have seen it.

It's in my digi-tech meter that I bought from Jaycar for $40 two years ago. it's even in the $12 Uni-T meter he linked you on eBay before ( http://www.ebay.com/itm/221270085516 - "relative" button ) - so it's not an uncommon feature at all.

It works like danb35 says on every meter i've come across - the only difference from a zero button on older meters is the name.

Yeah, the marketing people struck I think.  Anyway I need to go back and look for a real meter with a REL button since my old 1985 RS DMM died and it had a clear button.  I suppose people became so dumb, the noobs, that clear they must have been confused by and thought it was something else. /shrug

[peter.mitchell]

some sort of adjustable sample averaging, so adjustable resolution vs speed.

Maybe, but not sure how useful that would be.

More useful than you'd think imho, eg, could implement a feature where you hold a button and the sample rate shoots up at a lower resolution and logs the readings whilst the button is pressed, when released it stops logging and you can scroll through (Just an example, means you wouldn't have to reach for the scope as often ect)

i'd consider removing the rotary switch, possibly free up some front panel and internal space, i wish there was a nice way to be able to have the meter "saved" in a mode, so when you turn it on/off/on it is still in the same mode - this also fixes the issue of default turn on mode.

Maybe, Unlike twiddly knobs on scopes, I don't think (decent) buttons would be much worse than a rotary switch on a DMM, though may add expense for signal switching. May help reduce tooling costs though, but rotary does have the familiarity. Maybe buttons in a circle..!

There are a few more reasons for buttons imho, they help with one handed use, and if they are in an easily familiarisable(a real word? probs not)) position, much quicker than a knob.
With buttons, i don't like the idea of a "shift" button for extra modes/functions, i think you put the same multiple features on the button as you would on a multimeters knob (eg ohms, cont, diode), then you cycle through them by pressing the same button instead of pressing "shift > ohms" for cont, you just press ohms twice.

[EEVblog]

So lets say someone wanted to go ahead and actually make this thing (in small niche volume). What would be the best way to do it?
I'm thinking that finding a suitable host meter, rip it's guts out, and work around what you've got wouldn't be a bad way to go?

[Dark Prognosis]

So lets say someone wanted to go ahead and actually make this thing (in small niche volume). What would be the best way to do it?
I'm thinking that finding a suitable host meter, rip it's guts out, and work around what you've got wouldn't be a bad way to go?

Well, you are the king in that department so I smell a video coming RSN, lol.

[firewalker]

So lets say someone wanted to go ahead and actually make this thing (in small niche volume). What would be the best way to do it?
I'm thinking that finding a suitable host meter, rip it's guts out, and work around what you've got wouldn't be a bad way to go?

Perhaps the best way to start.

Alexander.

[Wytnucls]

So lets say someone wanted to go ahead and actually make this thing (in small niche volume). What would be the best way to do it?
I'm thinking that finding a suitable host meter, rip it's guts out, and work around what you've got wouldn't be a bad way to go?

A partnership of sorts with a Chinese manufacturer would be the way to go. Modify an existing DMM PCB to your requirements and let them make it for you. This is very much what Volcraft and others are doing with the UNI-T UT71 range. It's got most of the bells and whistles already and lots of open spaces on the PCB. You would need a fair volume order to make it worthwhile for them.

[jucole]

So lets say someone wanted to go ahead and actually make this thing (in small niche volume). What would be the best way to do it?
I'm thinking that finding a suitable host meter, rip it's guts out, and work around what you've got wouldn't be a bad way to go?

i'm thinking - pick a display then create the 2 part 3d model for the case front and back, create a pcb shape/s that will fit in nicely;  add some parts and make the rest up as you go along! ;-)

[EEVblog]

i'm thinking - pick a display then create the 2 part 3d model for the case front and back, create a pcb shape/s that will fit in nicely;  add some parts and make the rest up as you go along! ;-)

I think you underestimate how much work would go into designing a proper full multimeter case!
Given that the only thing that seems to be being re-invented here is the electronics and functionality, it seems rather obvious to me that an existing meter case could be very worthwhile considering.

[HackedFridgeMagnet]

Does it need to survive the canyoning test?

[mikeselectricstuff]

So lets say someone wanted to go ahead and actually make this thing (in small niche volume). What would be the best way to do it?
I'm thinking that finding a suitable host meter, rip it's guts out, and work around what you've got wouldn't be a bad way to go?

That's one approach, but issues like continuity of supply, printing and compromises come to mind. As well as finding something with the right sized display window. Certaiinly worth a look.

I'd say Plan A would be to look hard at existing cases from the Usual Suspects - Bopla, Okw, Takachi, Hammond etc. There are some with nice rubber boots, sealing, battery compartments etc. so I'd be surprised if there weren't a few decent candidates.
The Sharp 400x240 memory LCD is by far the stand-out choice for a display, so start with that and find a case that's a good fit for it, with the right sort of form factor and battery comprtment. Panel mount 4mm connectors would be fine.
Rubber membrane keypad probably a reasonable choice to help keep it waterproof - I have no idea what tooling cost is for these though.

[mikeselectricstuff]

Does it need to survive the canyoning test?

No, but some resistance to occsional dampness would be good. Maybe conformal coat the board if case sealing isn't brilliant.

[jucole]

I think you underestimate how much work would go into designing a proper full multimeter case!

meh;  well , first you need a concept - so here's mine :-)  now time to choose a display and decide on battery type.

[Dave]

Except that you now need a bluetooth adapter. None of my PC's have Bluetooth, and I suspect I am not alone. This makes USB a LOT more convenient!

C'mon, they're dirt cheap, I mean really cheap, just buy a dozen of these, bring them back home and start plug in each at every PC you can find. 

Just one problem: Bluetooth 4.0 (BLE) is not backward compatible with previous versions of Bluetooth. Cheap Chinese adapters will not work.

[FrankBuss]

I think you underestimate how much work would go into designing a proper full multimeter case!

meh;  well , first you need a concept - so here's mine :-)  now time to choose a display and decide on battery type.

Nice drawing. What do the buttons do? Looks like it could be transformed into a MP3 player with a firmware update, with the cursor keys to select a music, pause/play buttons and the rotary knob for the loudness I think it would be more useful to think about what functions you want, how they are displayed (menu, sub-menu, momentary functions etc.) and then decide what buttons you need.

[elgonzo]

Just one problem: Bluetooth 4.0 (BLE) is not backward compatible with previous versions of Bluetooth. Cheap Chinese adapters will not work.

Do you really need BLE for a multimeter which often is powered by a 9V brick (...i don't know...)?

Anyway, perhaps not exactly 'arse-cheap China price', but it still shouldn't break your bank:
http://www.amazon.com/GMYLE-Bluetooth-Technology-Wireless-Broadcom/dp/B007MKMJGO/ref=sr_1_2?s=electronics&ie=UTF8&qid=1380559926&sr=1-2&keywords=bluetooth+le

[elgonzo]

meh;  well , first you need a concept - so here's mine :-)  now time to choose a display and decide on battery type.

Ui... i would swap my MM just for your drawing 

[mikeselectricstuff]

Just one problem: Bluetooth 4.0 (BLE) is not backward compatible with previous versions of Bluetooth. Cheap Chinese adapters will not work.

Do you really need BLE for a multimeter which often is powered by a 9V brick (...i don't know...)?

Anyway, perhaps not exactly 'arse-cheap China price', but it still shouldn't break your bank:
http://www.amazon.com/GMYLE-Bluetooth-Technology-Wireless-Broadcom/dp/B007MKMJGO/ref=sr_1_2?s=electronics&ie=UTF8&qid=1380559926&sr=1-2&keywords=bluetooth+le

I don't know traditional BT well enough to know what power it draws to just hold a connection with minimal data transfer (e.g. for logging). Maybe it's fine, but on new kit it would seem sensible to support the latest spec if it might be useful, however it certainly should support old BT because it's so widespread already.
Could well be that the acquisition power is a lot more than the BTLE packet so maybe bog-standard BT would be fine  - thow would probably allow a cheaper Bt module to be used.
 

[echen1024]

Why not just have a rotary encoder with light up ranges on the side. Spin the switch, MCU keeps track, and the ranges light up to signify selected. Push the encoder twice, and the meter is off. Push once, and get the second function. Should be easy to implement as well.

[Monkeh]

Why not just have a rotary encoder with light up ranges on the side. Spin the switch, MCU keeps track, and the ranges light up to signify selected. Push the encoder twice, and the meter is off. Push once, and get the second function. Should be easy to implement as well.

Getting images of a rotary dial multimeter.

[JuKu]

Adding to the list of really nice features:
-A fast bar display in addition to the numbers
-True RMS
-AC bandwidth covers audio range (or at minimum, the 1kHz beep)
-(isolated) PC connection with logging, graphing and math function software
-as mentioned, very fast continuation test, with low enough voltage so that diode cpnnections are not opened.
-ESR for capacitors

[pickle9000]

Dials are fine buttons are fine but menu's suck. If going the button route one for acv one for dcv, resistance, esr, continutity amps and so on would be my preference. As for bluetooth I think it is the least painful. It would be interesting  if one meter could display information from another a few feet away, a purely soft feature but could be interesting.

 

[Marco]

Why not just have a rotary encoder with light up ranges on the side. Spin the switch, MCU keeps track, and the ranges light up to signify selected. Push the encoder twice, and the meter is off. Push once, and get the second function. Should be easy to implement as well.

How many positions would be necessary? For a very large number of detents I could see an encoder be the way to go, but single pole 12 position rotary switches are around 3 bucks and for 19 you have something like this for under 5 bucks.

[Lightages]

Speaking of using an existing design and dding the parts needed, I think I would try to partner with Uni-T using the UT71E as a basis. It has two M430 controllers plus the ES51966F multimeter chip. Certainly with this meter as a start there could be some really good things done. The inputs could also be re-engineered for proper protection to CATII 1000. That would be all that is needed for a purely electronics meter.

[mikeselectricstuff]

Adding to the list of really nice features:
-A fast bar display in addition to the numbers
-True RMS
-AC bandwidth covers audio range (or at minimum, the 1kHz beep)
-(isolated) PC connection with logging, graphing and math function software
-as mentioned, very fast continuation test, with low enough voltage so that diode cpnnections are not opened.
-ESR for capacitors

I thought bargraph so obvious it didn't need saying, however there would be scope to improve by user settable range and min/ max detect with persistance and fast attack/slow decay modes. High-res display would allow a much nicer bargraph display. Fortunately as memory LCD is line based (i.e you can only update a whole line), you could update a horizontal bargraph very quickly.
Or maybe a dual bargraph - a live bar as well as min/max markers above it.

[mikeselectricstuff]

Dials are fine buttons are fine but menu's suck. If going the button route one for acv one for dcv, resistance, esr, continutity amps and so on would be my preference. As for bluetooth I think it is the least painful. It would be interesting  if one meter could display information from another a few feet away, a purely soft feature but could be interesting.

Menus should only be for secondary functions and configuration - it should certainly be a single button for all major functions.

[Fsck]

Speaking of using an existing design and dding the parts needed, I think I would try to partner with Uni-T using the UT71E as a basis. It has two M430 controllers plus the ES51966F multimeter chip. Certainly with this meter as a start there could be some really good things done. The inputs could also be re-engineered for proper protection to CATII 1000. That would be all that is needed for a purely electronics meter.

I know few people (relatively) deal with HV electronics, but catIII 1kV wouldn't hurt.

[Dave]

Do you really need BLE for a multimeter which often is powered by a 9V brick (...i don't know...)?

I don't know about you, but if I had to keep my handheld multimeter on a leash, I'd probably shove it up its designer's arse.
You have bench multimeters for that.

[elgonzo]

Do you really need BLE for a multimeter which often is powered by a 9V brick (...i don't know...)?

I don't know about you, but if I had to keep my handheld multimeter on a leash, I'd probably shove it up its designer's arse.
You have bench multimeters for that.

The question was not whether Bluetooth makes sense, but rather if Bluetooth Low Energy (BLE) would be necessary for a multimeter (with regard to power consumption, compatibility, and perhaps costs). Having a BT interface makes perfectly sense, absolutely, yes.

[geostep]

Hmmm, maybe a supercap as an internal power source?

This won't work. Even a 100F supercap for 10 EUR stores only 1% energy of a typical AA battery (see this link). Digikey has a 1,000F supercap, but it costs 104 EUR and is 10x4cm. Let's talk again about supercaps when they've created something cheaper, smaller and better with nanotubes.

True. Point taken.  I was thinking of rapid recharge times. But as you say costs and battery energy density make it less than ideal.

- George

[EEVblog]

Why not just have a rotary encoder with light up ranges on the side. Spin the switch, MCU keeps track, and the ranges light up to signify selected.

Anything that "lights up" draws power, that's bad.

[EEVblog]

Speaking of using an existing design and dding the parts needed, I think I would try to partner with Uni-T using the UT71E as a basis. It has two M430 controllers plus the ES51966F multimeter chip. Certainly with this meter as a start there could be some really good things done. The inputs could also be re-engineered for proper protection to CATII 1000. That would be all that is needed for a purely electronics meter.

Yes, that is a good option. Even if you went the fully custom route, the ES51966F looks to be a good option on the surface. Great resolution, decent cap range, and micro interface. MSP430 would be a natural choice.
For the uCurrent like current, you could ignore the current inputs and switch in a x100 amp to the ADC some how. Or likely you'd simply use another simpler ADC hooked onto the MSP430 directly, with maybe 3 current input jacks. A, mA, and uA. That would even allow multiple current range measurement at once. Leave the trickier stuff like autoranging V/R/C to the ES51966F
That leaves the inductance measurement though.
Although could debate endlessly how much LCR capability you want in the meter. It could be a separate socket again and chipset.

[mikeselectricstuff]

BTLE will be essential to keep battery life reasonable. I looked at it for a work project and BTLE is two orders of magnitude better than classic BT for energy consumption.

The benefit does depend on exactly what you are doing though. It certainly should support BTLE, as you can spit out data in unconnected advertising mode for negligible power, but I think support for older BT would be necessary.
Do you happen to know what classic BT draws to just hold a connection open, when configured optimally?

[mikeselectricstuff]

Speaking of using an existing design and dding the parts needed, I think I would try to partner with Uni-T using the UT71E as a basis. It has two M430 controllers plus the ES51966F multimeter chip. Certainly with this meter as a start there could be some really good things done. The inputs could also be re-engineered for proper protection to CATII 1000. That would be all that is needed for a purely electronics meter.

Yes, that is a good option. Even if you went the fully custom route, the ES51966F looks to be a good option on the surface. Great resolution, decent cap range, and micro interface. MSP430 would be a natural choice.

Due to need to support a graphic display, I think you'd be looking at something like the EnergyMicro ARMs, at least for the display and UI handling. may be some merit in having a small slave MCU for the measurement system, especially if it has a good enough onboard ADC, however an external ADC may give better performance at similar cost

That leaves the inductance measurement though.

That would be on the "nice if you can do it at minimal cost" list, not worth spending extra hardware for.

Although could debate endlessly how much LCR capability you want in the meter. It could be a separate socket again and chipset.

I think in terms of LCR, just the performance to identify E12 caps and inductors over a decent range is adequate. range is probably more useful than accuaracy, but should be limited to what's practical without increasing cost or complexity.  Obviously R is already covered. A rough ESR function, enough to ID obvously bad electrolytics would be good. Bonus points if it's good enough to tell the difference between a NPO/COG dielectric and X/Y type

Seperate socket - maybe - could make protection easier if you assume the user is not dumb enough to plug it into the mains

[EEVblog]

Do you happen to know what classic BT draws to just hold a connection open, when configured optimally?

Try:
http://nesl.ee.ucla.edu/fw/documents/reports/2007/poweranalysis.pdf

[jucole]

I think you underestimate how much work would go into designing a proper full multimeter case!

meh;  well , first you need a concept - so here's mine :-)  now time to choose a display and decide on battery type.

Nice drawing. What do the buttons do? Looks like it could be transformed into a MP3 player with a firmware update, with the cursor keys to select a music, pause/play buttons and the rotary knob for the loudness I think it would be more useful to think about what functions you want, how they are displayed (menu, sub-menu, momentary functions etc.) and then decide what buttons you need.

After sketching out a concept UI last night;  I can do away with the "mp3 play" :-)  button but keep the other one, which is an "options" button.  My meter has 2 basic functions; one to measure, and the other to be a small power supply to power my small projects - hence the dial for setting the voltage / current.

Mine will use a 9V battery and a generic external DC source if you want to use the power supply feature and the more power hungry features without killing your battery.   I noticed also by removing the range switch you free up some nice board space.

The 3d model will require a lot of detail; especially the inner part, before it can be sent to a commerical 3D printer.

[BravoV]

Even if you went the fully custom route, the ES51966F looks to be a good option on the surface.

This with an assumption that Cyrustek willing to share the technical details on that chip with this project team (with/without NDA)  , and also have a feeling that the chip order quantity is not going to impress their sales team. 

I hope that I'm wrong.

[mikeselectricstuff]

Do you happen to know what classic BT draws to just hold a connection open, when configured optimally?

Try:
http://nesl.ee.ucla.edu/fw/documents/reports/2007/poweranalysis.pdf

..so too much for continuous logging, but probably still useful for download/FW updates and occasional live use. I'm a bit dubious about how it can be 2mw for 1280mS sniff rate and 9mW for 470ms though. This study also seems to be looking more at power vs., bandwidth as opposed to minimum achievable power at negligible bandwidth, the latter and will probably be more  dependent on the actual chipset as tx time will be minimal.

A nice BT feature might be to be able to pretend to be a BT keyboard, and spit readings out as if they were keypresses.
Looking at a few random BT keyboards, it looks like a standby power draw somewhere between 0.3 and 1mA is achievable, which would be pretty tolerable for medium-term logging applications

[EEVblog]

Due to need to support a graphic display, I think you'd be looking at something like the EnergyMicro ARMs, at least for the display and UI handling. may be some merit in having a small slave MCU for the measurement system, especially if it has a good enough onboard ADC, however an external ADC may give better performance at similar cost

Sure, that would be the next step up, whatever is needed. Those two would be my first choices in both cases.

That would be on the "nice if you can do it at minimal cost" list, not worth spending extra hardware for.

And so begins the compromise over feature set. Next thing you know, there's not much to differentiate it from a COTS meter.

Seperate socket - maybe - could make protection easier if you assume the user is not dumb enough to plug it into the mains

If you are rolling your own meter, separate sockets are pretty much a no-brainer I think.
People expect to swap leads for current, so no problem for other stuff.

[mikeselectricstuff]

That would be on the "nice if you can do it at minimal cost" list, not worth spending extra hardware for.

And so begins the compromise over feature set. Next thing you know, there's not much to differentiate it from a COTS meter.

The whole point is to see how you can make a multimeter more useful within the typical cost and form factor, not make the best, do-it-all device.
Go back to the scope analogy - over recent years, scopes, have improved dramtically in terms of display, size/weight and additional ways of looking at data (decode, deep memory, colour etc.), but they still do the same basic thing, display signals over time. over similar ranges of voltage/frequencies to scopes  of 20 years ago, but at a much lower price. Nobody is building full-function logic analysers, spectrum analysers (apart from FFT) etc, into them.
In comparison the DMM has barely changed over the last 10+ years.
In terms of usefulness, inductance measurement comes pretty low down the list compared to things like the various display, audio and connectivity things discussed so far.
Apart from IDing unmarked SMD devices, how often do most people need to measure inductance?  Maybe testing /IDing transformer pins, perhaps making an RFID antenna - can't think of anything else I've used one for.

I don't think inductance measurement would be worth spending any significant money on compared to other things discussed so far, whearas things like low capaitance ranges can be useful, and  for more than component testing - e.g. finding which end of a cable is open without opening the plug. Unlike capacitors, the only likely failure mode of an inductor is open,  so inductance isn't an especially useful faultfinding tool. 

[EEVblog]

..so too much for continuous logging, but probably still useful for download/FW updates and occasional live use.

Yes. I don't why you'd want to sit there live for long periods and watch paint dry anyway in most cases you'd use such a meter for. If you wanted to update your data you could have a simple "update data" button and it would turn on the TX and send the latest data and then shut down again.

Live logging is not such an important feature you'd sacrifice battery life for, or change the battery design for for example. Logging is seldom used feature on most meters anyway.

[EEVblog]

The whole point is to see how you can make a multimeter more useful within the typical cost and form factor, not make the best, do-it-all device.

But unless you are very serious about production, you won't be able to make it look and feel (and be certified) like a real meter.
You have differentiate whether this is simply a "wish list" exercise for a commercial meter, or a worthwhile design someone would/could take into the real world.
If it's the latter, then I think you really do have to add very unique value in some way that the current crop of meters do not do. That is why my old video had novel stuff like 4 isolated channels for example.

In terms of usefulness, inductance measurement comes pretty low down the list compared to things like the various display, audio and connectivity things discussed so far.
Apart from IDing unmarked SMD devices, how often do most people need to measure inductance?  Maybe testing /IDing transformer pins, perhaps making an RFID antenna - can't think of anything else I've used one for.
I don't think inductance measurement would be worth spending any significant money on compared to other things discussed so far, whearas things like low capaitance ranges can be useful, and  for more than component testing - e.g. finding which end of a cable is open without opening the plug. Unlike capacitors, the only likely failure mode of an inductor is open,  so inductance isn't an especially useful faultfinding tool.

Yep, there is a reason why multimeters have not really evolved to have inductor measurement, it's because it is seldom needed. And when you need it, any half decent lab has an LCR meter to do the job much better than a compromised multimeter function ever could. Capacitance on the other hand has many uses, e.g. broken cable checking/length checking.

[mikeselectricstuff]

The whole point is to see how you can make a multimeter more useful within the typical cost and form factor, not make the best, do-it-all device.

You have differentiate whether this is simply a "wish list" exercise for a commercial meter, or a worthwhile design someone would/could take into the real world.
If it's the latter, then I think you really do have to add very unique value in some way that the current crop of meters do not do. That is why my old video had novel stuff like 4 isolated channels for example.

No particular agenda, and certainly no intention to actually build something - just wanted to discuss what could be possible ( aside from any marketing BS issues) , and why DMMs haven't changed in the same way that scopes have over the years.
Some of the things proposed would be completely trivial to implement (e.g. better audio alert functionality) and very useful (although you do risk hitting the user interface limitation with a segment LCD).
But none of the big makers seem to have the imagination to truly innovate in the DMM field in the same way as they have in scopes.
Look what we've seen recently as supposedly 'new innovations' - Fluke wireless ( proprietary, expensive) , Agilent OLED ( pointless waste of power), Agilent bluetooth (ugly add-on lump with another battery), and.... er, I can't actually think of anything else.... pretty pathetic really.

[FrankBuss]

This with an assumption that Cyrustek willing to share the technical details on that chip with this project team (with/without NDA) 

The datasheet looks very complete, no need for a NDA:
http://www.cyrustek.com.tw/spec/ES51966A.pdf
application circuit included. They have some other versions as well:
http://www.cyrustek.com.tw/product-1.htm

and also have a feeling that the chip order quantity is not going to impress their sales team. 

Right, buying the right $2 multimeter at eBay and then desolder it might be cheaper than low quantities of the chip, and you get a battery for free But there is an eMail on the website, you could ask the sales contact.

But would be more interesting to implement your own dual slope ADC with a microcontroller, an op amp etc.

[jucole]

For the uCurrent like current, you could ignore the current inputs and switch in a x100 amp to the ADC some how. Or likely you'd simply use another simpler ADC hooked onto the MSP430 directly, with maybe 3 current input jacks. A, mA, and uA. That would even allow multiple current range measurement at once. Leave the trickier stuff like autoranging V/R/C to the ES51966F
That leaves the inductance measurement though.

On page 23 of the ES51966 datasheet it shows an additional ADC on pin 31 labelled "V400m" which is a 400mV independent input which you can use for other stuff - I only know that because I was playing around creating a schematic of one of their similar chips.

[echen1024]

In terms of a DAC, I think that a 24bit Linear chip, with 6.5 digits would be really impressive. The only other meter that does this type of resolution is a prohibitively expensive Gossen meter.

[Wytnucls]

Speaking of using an existing design and dding the parts needed, I think I would try to partner with Uni-T using the UT71E as a basis. It has two M430 controllers plus the ES51966F multimeter chip. Certainly with this meter as a start there could be some really good things done. The inputs could also be re-engineered for proper protection to CATII 1000. That would be all that is needed for a purely electronics meter.

Some, if not all the UT71 PCBs, have been reworked by UNI-T to cater for HRC fuses. Hopefully, that includes the 71E, so there is even less work to do now

[echen1024]

In terms of batteries, wouldn't an off the shelf Li-Po cell phone battery work? I know that ZeroLemon batteries have this 7000 mAh battery for $35. This could allow us to use fancy LCD displays, and selectable current for a programmable diode test, all without a battery life sacrifice. I'm also sure that we could get some bulk discount if we purchase a large quantity.

http://www.amazon.com/warranty-ZeroLemon-Extended-Protection-Compatible/dp/B00AKZWGAC/ref=sr_1_1?ie=UTF8&qid=1380672258&sr=8-1&keywords=zerolemon

[casinada]

f you need a Microcontroller that has everything including the Kitchen sink:
http://www.ti.com/product/msp430f67791
7 channel 24 Bit ADC
8 channel 10 bit ADC
RTC
Temp sensor
DMA
Can drive 320 LCD segments, etc, etc, etc...................
$6.50 in 1K quantities
 

[EEVblog]

On page 23 of the ES51966 datasheet it shows an additional ADC on pin 31 labelled "V400m" which is a 400mV independent input which you can use for other stuff - I only know that because I was playing around creating a schematic of one of their similar chips.

Ah, handy, I thought that was the reference input. I've only glanced at the datasheet.

[mikeselectricstuff]

In terms of a DAC, I think that a 24bit Linear chip, with 6.5 digits would be really impressive. The only other meter that does this type of resolution is a prohibitively expensive Gossen meter.

High accuracy is about a lot more than just the ADC. Reference stability, TC of every component in the analogue path, thermocouple effects, PCB surface leakage etc. etc. etc.
And you don't need 6.5 digits in an everyday multimeter

[echen1024]

That is probably the main problem. As we have seen in the previous post on 6.5 digit multimeters, it should be possible to get around 0.025% initial accuracy, plus, this can be just a modular plugin for people who need the 6.5 digits.

[jucole]

this can be just a modular plugin for people who need the 6.5 digits.

Since my previous post i've dropped my modular idea; so If you want to "pimp" your meter, you'll have to swap-out the entire front-end board.

[Marco]

f you need a Microcontroller that has everything including the Kitchen sink:
http://www.ti.com/product/msp430f67791

Interesting micro, but unless the data-sheet is exaggerating the INL ain't so hot at 100 ppm.

[echen1024]

this can be just a modular plugin for people who need the 6.5 digits.

Since my previous post i've dropped my modular idea; so If you want to "pimp" your meter, you'll have to swap-out the entire front-end board.

 . Only we can think of the term 'pimp your meter'. Also, what about batteries. Why don't we just use off the shelf big cellphone batteries. The meter doesn't exactly have to be 'sexy', per say, but with a big battery, we could do an OLED display, square wave gen like on the 1253, and an adjustable current Diode test.

[jucole]

ok my last post - which is a rough ui mockup based on my 4 channel DMM concept drawing; basically you can assign a mode operation to each channel via the top row buttons.

[Fsck]

this can be just a modular plugin for people who need the 6.5 digits.

Since my previous post i've dropped my modular idea; so If you want to "pimp" your meter, you'll have to swap-out the entire front-end board.

 . Only we can think of the term 'pimp your meter'. Also, what about batteries. Why don't we just use off the shelf big cellphone batteries. The meter doesn't exactly have to be 'sexy', per say, but with a big battery, we could do an OLED display, square wave gen like on the 1253, and an adjustable current Diode test.

instead of big ass oddly shaped batteries, I'd suggest 18650s as they're pretty much standard around the world wherever there is li ion.

[mamalala]

Also, what about batteries. Why don't we just use off the shelf big cellphone batteries.

I think that it would be rather stupid to do so. You never know if they will be still available in a few years from now. Better to use standard cells that will probably be around for some more decades to come.

Greetings,

Chris

[echen1024]

Probably. I just wanted a higher energy density...

[MasterOfNone]

As technology advances, things that were impractical can become practical, so maybe the DMM as we know and love it is ultimately doomed.
It’s possible that the DMM may not really evolve much more, instead they could be phased out, replaced by small & light  Scopemeters that can also operate as data loggers. The data logger could operate at a lower rate but higher precision than the scope function, giving you the option to plot things like drift etc, rather than the standard peak hold on a typical DMM. 
Once you get rid of the rotary knob on the DMM there is a lot of extra screen space.

[jerry507]

I'd caution putting too much thought into the exact button configuration until you consider the entire UI at the same time. Trying to fit a menu structure to the buttons will never turn out as well as completely integrating the choices of buttons/other control elements and the menus.

I think there's a lot of great ideas here. I like the idea of having integrated efficiency measurements. Wouldn't that be as simple as using dual converters and a common terminal? A dedicated current measurement unit and a dedicated voltage measurement unit. No switching between current/voltage.

Many great ideas

[ludzinc]

ok my last post - which is a rough ui mockup based on my 4 channel DMM concept drawing; basically you can assign a mode operation to each channel via the top row buttons.

I'm intrigued about how you'd be able to implement a 'soft button' multimeter.

The thing about a physical range switch, is that it makes switching so easy.  If you look here (figure 1):

http://www.circuitstoday.com/electronic-multimeters

You see a typical example of the range switching for voltage measurements.

How can this be done under control of a micro? 

You could use reed relays, but that will just sky-rocket the cost, so that option is out pretty much straight away.

Analogue multiplexers seem like a good idea (example here: http://www.analog.com/en/switchesmultiplexers/multiplexers-muxes/adg1608/products/product.html) but you will soon stress their input voltage limits (of course you can build in protection, but that's extra complexity and cost). 

For example on a 200V range, you might be measuring the voltage across the last resistor tap in the input string, but the uppermost tap will be subject to the full 200V and thus too will your mux protection circuit.

Methinks a simple diode clamp isn't going to cut it here.

Happy to hear your thoughts on this, very happy to be shown I'm wrong and that this is a easily surmounted problem!

[ludzinc]

.. forgot to add.  Any protection scheme that comes to mind for me that's effective at high voltages, soon falls over when you invert the polarity (i.e. a 5V zener will clip your negative signals to -0.,7V etc).

[Napalm2002]

All I know is I want in. Ac+dc is a must. Esr is a must.


Sent from my iPhone using Tapatalk - now Free

[jucole]

ludzinc

Dave did a superb video called "EEVblog #373 - Multimeter Input Protection Tutorial"  other great resources are auto-ranging DMM schematics and DMM chipsets.

One DMM in particular that was of interest to me was the "Tektronix TX3" and the reason why was because it had only 1 jack socket for measuring Amps - which I thought was a great feature!
If you look on PDF page 48 (section 3-2) of the service manual you'll see how they did it. http://www.testitnow.co.uk/media/files/test_equipment_manuals/Tektronix/Tektronix%20TX3%20(PN%20070-9893-01)%20Service%20Manual.pdf

[ludzinc]

ludzinc

Dave did a superb video called "EEVblog #373 - Multimeter Input Protection Tutorial"  other great resources are auto-ranging DMM schematics and DMM chipsets.

One DMM in particular that was of interest to me was the "Tektronix TX3" and the reason why was because it had only 1 jack socket for measuring Amps - which I thought was a great feature!
If you look on PDF page 48 (section 3-2) of the service manual you'll see how they did it. http://www.testitnow.co.uk/media/files/test_equipment_manuals/Tektronix/Tektronix%20TX3%20(PN%20070-9893-01)%20Service%20Manual.pdf

Thanks very much.

Dave's video solved the protection question, and that makes bipolar multiplexers useful here.

Cheers.

[JOERGG]

High voltage (30V) diode test for zeners,  LED strings (e.g. LCD backlights) . cost : A few cents for a crude DC-DC step-up

Low Voltage (0.2V) diode test or ohms for my sake, have a Hi - Lo (3V - 0.2V) switch on my 30 years old Voltcraft 7905a. Very useful when probing resistors in circuit without opening transistors or diodes. It is for me like the possibility to split the circuitry into sections when i try to find a short circuit.