POLL: New µCurrent Design

[dannyf]

Please explain further on the "better performance" part.

Most times, those parts are designed to meet the following top goals: looks, looks and looks.

[Zad]

If you made it a fixed range unit, you could make a whole set of them. People would then inevitably buy several of them, they would be easy to calibrate, more robust and cheaper to build. Oh yes, and more profitable. It might also make it easier to move to a transimpedance amplifier design with zero burden.

[EEVblog]

If you made it a fixed range unit, you could make a whole set of them.

I had that fleeting thought...

[EEVblog]

A solution could be to simply leave the top half of the case off, and just use the bottom. Effectively just like the old design uCurrent. The screws hold the PCB in place, the battery (top side) can be removed without undoing the case, and the switches and LED are accessible on the top side along with PCB labelling.
Yet it would still have a bottom to protect the components and provide some grip for handling.
Too bad the Hammond case lip isn't lower to the PCB level or below, but spacers could be used perhaps.
I've considered this a long time back and these cases are pretty nice for this purpose:
http://www.altronics.com.au/download/ndb/specifications/h/H0212.pdf
Removable end panels allow connectors to protrude without holes

[free_electron]

You forgot the slide switches and LED.
Labelling?
This approach is getting a bit messier than my old uCurrent design.

labeling is not an issue. you use one red and one black terminal. the output is in line with input so no markings needed there.
led is a hole inbetween the input bananas.

switch is not an issue. when i did the JW pulser i lasercut (makerspace) a piece of plexiglass with the position for the led and the slit for the switch. this plexi slid in place over the internal screw posts.

i have a very simply column drill with an x-y screw-vice. put in a milling bit and 20 seconds cuts you the slit. the plexi is your guide.

[EEVblog]

labeling is not an issue.

The range switch needs labelling.

i have a very simply column drill with an x-y screw-vice. put in a milling bit and 20 seconds cuts you the slit. the plexi is your guide.

The regular Joe isn't going to be able to cut their own switch slots.

[Stonent]

New idea. uCurrent uWatch!

Just put it all together!

[ElectroIrradiator]

I vote for an encased design of reasonable mechanical strength, preferably a plug-in design.

[bookaboo]

I liked the old style just fine

- The case adds practically zip to the cost
- If battery life is an issue just adda 2way header in parallel, people can hack in their own bat pack inside the case.
- "Not having leads" isn't that big an issue, I just keep mine in a small box with leads.
- I see mechanical stress issues if it's made to plug direct to multimeters. Over time those connections will get worn with wiggling to connect and disconnect.

[tld]

Biggest challange with µCurrent has often been price and availability.  Other than that, formfactor is less important.  If it's be possible to get "something" below AUS 30-35, that'd be below some customs-limits, which really change pricing.  Effectively, costing AUS 36 will often be 50-100% more expensive than costing AUS 35.

I know I might be asking a lot, but having a version below that price-point (below AUS 30 for safety against currency-fluctuations) would make it a no-brainer to buy for a lot of us, while it's a medium expense now.

Even if it's just the bare PCB, bare PCB with hard to get parts, or complete kit.

[TMM]

The only issue i have with the rev3 design is the current input terminals. If the threaded section was a little longer it would make them a bit better to use with deep shrouded banana plugs and crocodile clips (yes i know, bad habit using croc clips in banana jacks...).

I am quite happy with the rev3 form factor and you could easily fit a beefier switch for higher current. Jumpers are for 'set and forget' configuration, not the main range switch on test equipment imo.

I'm all for the plug-in idea with the existing form factor or smaller as long as it doesn't compromise on features/accuracy.

[free_electron]

labeling is not an issue.

The range switch needs labelling.

i have a very simply column drill with an x-y screw-vice. put in a milling bit and 20 seconds cuts you the slit. the plexi is your guide.

The regular Joe isn't going to be able to cut their own switch slots.

Not if you make it fixed range.
On off and range could be 1 switch. Those slide switches have two sides with three notches each. Use one side for power, one for range.

You would have to mill the slot. I did that too for the jw pulser.

[veryevil]

Hey, this sounds really interesting.

I've got 2 uCurrents and the one big issue I have with them is the limited range being tied to the 3v battery +- 1.5v I often find it clipping. I see the new chip is still only +- 2.5v max is there a similar chip that has a higher input voltage range allowing much larger range?

[AG6QR]

I've got an original classic uCurrent, and am unlikely to need another, so I'm not a likely future customer.  That said, I want to be able to throw the device in a drawer or toolbox along with a bunch of other devices and not worry about it until I need it.  So I'm not crazy about a PCB with exposed parts, contacts, and traces that could be subject to ESD damage or could be damaged by shorting out.  Also, I really prefer switches to jumpers.  I might accept a jumper on the condition that the jumper is ALWAYS installed on some set of terminals, so it can't be easily misplaced.  But I'd complain about it.

My preference, in order:

• A smaller, fully enclosed case that plugs directly into the meter, similar to the common thermocouple adapters shown earlier in this thread.
• The original classic design.
• A small, bare PCB that plugs directly into the meter, similar to the resistance adapter shown in the first post.

In other words, I value having a full enclosure around the electronics more than I value miniaturization.

I like the original uCurrent packaging.  I'd prefer to omit the binding posts and have the inputs be banana jacks like the outputs are.   The binding posts are bulky protrusions, and since I always end up plugging banana plugs into them, the bulk is a waste as far as I'm concerned.  Ideally, I'd like shrouded banana jacks, so I can easily use the same probes I already use with my meters.  But unshrouded banana jacks, just like are currently used on the output side, would be an improvement for the input side, in my book.

As for cost, I think the original design was a fair value.  If a bare pcb version were around 60% the cost of the original, it would be tempting.  A version in a "thermocouple adapter" style plug-in case would be worth maybe a 40% premium over the original design.  On any version, I think the difference between a jumper and a switch is worth around 20% or 30% the total price of the device.

[EEVblog]

You would have to mill the slot. I did that too for the jw pulser.

I don't want to mill anything.
I am trying to make it simple and reduce costs, these aren't low volume one-off's here, stuff like that adds up in production. I'd go back to the old design before I have to mill slots in stuff.

[EEVblog]

My preference, in order:

• A smaller, fully enclosed case that plugs directly into the meter, similar to the common thermocouple adapters shown earlier in this thread.
• The original classic design.
• A small, bare PCB that plugs directly into the meter, similar to the resistance adapter shown in the first post.

What about a plug-in enclosed bottom that protect the circuits, but an exposed top that has the battery, switches, and labeling? Just like the old design, but with battery on top?

[free_electron]

You would have to mill the slot. I did that too for the jw pulser.

I don't want to mill anything.
I am trying to make it simple and reduce costs, these aren't low volume one-off's here, stuff like that adds up in production. I'd go back to the old design before I have to mill slots in stuff.

ah. ok. I thought you were going to make a more upscale version. i saw the 'GOLD version' in the inital post and assumed that this was the gold version, but apparently you want to make an economy version now. my mistake

I'd like to have one similar to what i proposed. Simple box , plug it in between meter and cables. Nice looking and well built. I'd spend 10$ more on a 30$ microcurrent if it sat in a box like i've shown with icely milled holes and slots. I'm not fond of bare boards, protruding stuff you can touch.. but that's personal taste and not what you are after .

Still it may be worth investigating what a company would charge to machine the plastic for you. It may not be that expensive in quantity.

[EEVblog]

Still it may be worth investigating what a company would charge to machine the plastic for you. It may not be that expensive in quantity.

It is unfortunately, unless you want to go to deepest darkest parts of china. Hammond will machine and silk screen their boxes for you, but it is far from cheap.

[AG6QR]

What about a plug-in enclosed bottom that protect the circuits, but an exposed top that has the battery, switches, and labeling? Just like the old design, but with battery on top?

I'd be concerned about the possibility of shorting out the battery if it were exposed.  Imagine throwing the device in a toolbox full of screws, nails, wires, and other conductive metal objects of various shapes and sizes.  If you can guarantee that there's no danger of a short circuit, I'd think the design you're proposing would be an improvement over the original design. 

Realistically, I wouldn't abuse the thing that badly, but I might want to store the device in a drawer that might contain a test probe or two, with some exposed metal.  I can also imagine a small thing like that occasionally being carried in a pocket along with car keys and change, not that I'd personally try such a thing.

[george graves]

What's your thoughts on the old "plexiglass sandwich" type of case?

[Fsck]

I find the plexiglass sandwich too vulnerable personally.
I really like my cases to have solid sides all the way around

[EEVblog]

What's your thoughts on the old "plexiglass sandwich" type of case?

They were ok at first for some things (and still are), but now it seems everyone is doing it regardless of whether it's the best way or not.
For something like the uCurrent I'd rather have an open top and side walls to grip.
Like this very crude mockup attached.
The paper mockup isn't accurate, you'd screw into the case holes instead of the PCB holes, so more like the real PCB pictured.
This case is available from many sources, costs a dollar or so in volume, you can use both halves (halving your cost). No cutouts or machining required, no front panel silkscreen or label required, and you can change the battery (on top of PCB) without unscrewing the case. And can use either the gold binding posts as proposed in the GOLD version, or the right angle 4mm banana sockets as proposed by free_electron
Yeah, it's not pretty, but it's cheap and circuitry is adequately protected.
There is a deeper version of the same size.
In fact if the battery is put on the underside with the circuitry, then it's essentially the same as the old design, but has a shallower case, and plugs direct into the meter.

[EEVblog]

Hmm... if those binding posts are moved down a bit, I could put an SMD CR2032 battery holder on the underside of the PCB on the top. No messy battery on the front panel, more room for big labels and name etc, and you can change the battery without unscrewing.

[Fsck]

The mockup is pretty clever, sort of the best of both worlds. I'm totally for it.

[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.