POLL: New µCurrent Design

[David_AVD]

One thing I'm not fussed on are plug-in DMM adapters that stick up too far.  The longer they are the easier they seem to break.

[EEVblog]

Good idea. I'd probably face the uCurrent the other way so if you have the meter propped up the uCurrent is facing up (PCB side up). It's not a big deal either way though since reversed polarity is not an issue for 99% of meters.

Some meters will need it one way, some the other way. So the polarity choice in the design is a bit arbitrary.

[Lightages]

Dave:

If you do make the new uCurrent a direct plugin, then you need to account for meters that do not have a flat face. Have a look at the Brymens to see the concern. The middle two jacks are recessed a bit into the face because of the curved front.

[pickle9000]

Dave, would the jacks be staying at the top or would you move them closer to the meter to reduce mechanical stress?

[EEVblog]

One thing I'm not fussed on are plug-in DMM adapters that stick up too far.  The longer they are the easier they seem to break.

Unfortunately this case only comes in this length (90mm), and most that space is needed anyway if the battery goes on the back side.

[EEVblog]

If you do make the new uCurrent a direct plugin, then you need to account for meters that do not have a flat face. Have a look at the Brymens to see the concern. The middle two jacks are recessed a bit into the face because of the curved front.

Good point.
Just tried the BM869, and damn, they are recessed in a long way. My mock-up didn't fit as it was, I had to remove the case. But that would be the correct distance in production I think.

[EEVblog]

Dave, would the jacks be staying at the top or would you move them closer to the meter to reduce mechanical stress?

Good point. No real reason they can't be close to the base.

[EEVblog]

I think I'll be implementing production testing into the panel as well this time, allowing 10 boards to tested at once. Should've done that way back, but was always "only a few hundred more" 

[pickle9000]

Where you thinking of closing off the top of the case with a routed out bit of pcb?

[EEVblog]

Where you thinking of closing off the top of the case with a routed out bit of pcb?

No, the top of the case would have the CR2032 battery access, perhaps sticking out a bit so you can grab it. Don't know, haven't looked at suitable SMD holders yet.

[neggles]

If you do make the new uCurrent a direct plugin, then you need to account for meters that do not have a flat face. Have a look at the Brymens to see the concern. The middle two jacks are recessed a bit into the face because of the curved front.

One thing I'm not fussed on are plug-in DMM adapters that stick up too far.  The longer they are the easier they seem to break.

It's relatively easy for an end-user to unsolder the banana plugs and solder on small (2-3") flying leads with banana connectors attached if their meter doesn't have the standard spacing or has recessed banana sockets.

Perhaps this could even be offered as an option for a dollar or two more, as short male-male twin banana leads are available for under $1 in quantity (split in half, use one half for each unit) - or optionally just with no connectors included on the DMM end for an end user to add their own.

[TMM]

Good idea. I'd probably face the uCurrent the other way so if you have the meter propped up the uCurrent is facing up (PCB side up). It's not a big deal either way though since reversed polarity is not an issue for 99% of meters.

Some meters will need it one way, some the other way. So the polarity choice in the design is a bit arbitrary.

That didn't even cross my mind heh. All my meters have the +ve on the right and gnd on the left. Even with the same meter it could be preferable to have it in different orientations when using the meter standing or lying down. If the range/power switch were on the edges it wouldn't matter which way it ended up but that could make the case difficult to implement. Another idea would be to have configurable input polarity with a switch or jumpers.

Also, changing the aspect ratio so it is wider than it is long will reduce the ability of it to obscure the meter's display when lying flat on a desk and leverage on the plugs/jack.

[alm]

I like the idea of a plug-in version (less bench space and messy wires), but I would be worried about mechanical integrity. The low Ohms adapter is much smaller, and I expect the Fluke thermocouple adapter to have its plugs mounted to the case, not just soldered to the PCB (I realize this is a mock-up). Is there anyway you can provide extra mechanical support for the male banana plugs?

How common is it for DMMs to have a jack spacing other than 1.75"? I think this may be somewhat common in cheaper DMMs. So an easy way to convert it to female banana jacks would be nice.

[TimNJ]

I like the idea of a plug-in version (less bench space and messy wires), but I would be worried about mechanical integrity. The low Ohms adapter is much smaller, and I expect the Fluke thermocouple adapter to have its plugs mounted to the case, not just soldered to the PCB (I realize this is a mock-up). Is there anyway you can provide extra mechanical support for the male banana plugs?

How common is it for DMMs to have a jack spacing other than 1.75"? I think this may be somewhat common in cheaper DMMs. So an easy way to convert it to female banana jacks would be nice.

You could do a panel mount banana jack and then run a short low-R wire to the board.

[alm]

That would be my solution, but it would increase assembly costs, and Dave has expressed a dislike for wired connectors in his discussion of the previous µCurrent design.

[Dave]

How common is it for DMMs to have a jack spacing other than 1.75"? I think this may be somewhat common in cheaper DMMs. So an easy way to convert it to female banana jacks would be nice.

Pretty much every multimeter I have ever encountered had the standard 0.75" (19.05mm) input jack spacing. I don't think you will find any decent meters on the market, that don't use the standard spacing. Maybe some shitty one-hung-low branded, but then again, if you do have a meter like that, you probably won't need a uCurrent adapter.

[pickle9000]

Universal mounting,

Assuming the board is wide enough you could just place the negative close to the center of the board the two positives on either side. Mount the plugs as usual but thus would allow the user to change them if reversed. As for jacks a hole large enough to mount a wire would be a good idea (or even a couple unpopulated jack mounts, that would look messy though, I hate messy). 

[AG6QR]

Pretty much every multimeter I have ever encountered had the standard 0.75" (19.05mm) input jack spacing. I don't think you will find any decent meters on the market, that don't use the standard spacing. Maybe some shitty one-hung-low branded, but then again, if you do have a meter like that, you probably won't need a uCurrent adapter.

Right.  And on the off-chance that you really do need to adapt it to a non-standard spacing, all that's required is a standard pair of stackable banana plug leads.  All the ones I'm familiar with will accept male or female banana plugs or jacks.  It might leave some connections with exposed uninsulated metal, but at the voltages involved, that ordinarily shouldn't be a safety risk.

There's no need to do anything special to allow for non-standard spacing.

[reagle]

I realize this is not a direct answer to the poll question, but my two annoyances with the existing uCurrent so far have been:
Forgetting to turn it off and killing battery. An auto-off would be nice.  And secondly, a limited frequency response. When dealing with all things wireless, you get a short "chirp", and then it jumps down to sleep/hibernation current. The shape of that chirp is usually not very accurately reproduced if I have a scope connected to the uCurrent. But since this is mostly a DMM accessory, maybe that's was not a design goal in the first place.
Case-wise, making it less tall would be nice.

[trevwhite]

It would be nice to measure processor current for various peripherals being turned on and off. For example turning on the ADC of a processor, making a measurement and then turning it off again could take literally 10uS. This unit would not be able to display this current change if connected to a scope would it?

This kind of performance is more important than cost

Trev

[AG6QR]

It would be nice to measure processor current for various peripherals being turned on and off. For example turning on the ADC of a processor, making a measurement and then turning it off again could take literally 10uS. This unit would not be able to display this current change if connected to a scope would it?

In one of the first posts on this thread, Dave mentioned that the new version uses an improved amp with better performance to 30kHz.  That's getting into the right order of magnitude to see 10uS, but perhaps not quite all the way there, especially not if you demand high precision.

[trevwhite]

Maybe there is the option to upgrade the unit aftermarket with a better proposed op amp? Keep the initial cost down but provide an upgrade path for higher performance?

[geo_leeman]

Maybe there is the option to upgrade the unit aftermarket with a better proposed op amp? Keep the initial cost down but provide an upgrade path for higher performance?

That seems like a lot of fuss for "minor" changes. 

I do like the plug in idea, but with a case to protect it.  I often carry my gear to multiple labs in a bag and a free circuit board would not last.  For me removing a couple of screws to replace the battery just isn't a big deal.  I'd rather have a sturdy instrument with no shorting hazard.

[george graves]

Just a pet peeve of mine is the 5 different fonts types.  The rule of thumb is only use two.  Pick two, and that's all you get.

I hope you've been shooting some video blog stuff as you've gone through the changes!  Would love to see what you're dealing with!  Would thumbs up!

[EEVblog]

Just a pet peeve of mine is the 5 different fonts types.  The rule of thumb is only use two.  Pick two, and that's all you get.

It is only two fonts!
Arial and Maiandra