Multi Channel Input/Output instrument design

[jfsimon]

Good morning,
I fininshed the first prototype of this 4 channel DC Meter, hardware & software.
It is a 2 x 0-10Vdc + 2 x 30Vdc inputs that connects to a computer for readback.

The software is yet very simple, useful additional functions can now be impleented;

I'm looking for people interested to review and eventually test the units.
I suggest sending material to people interested for tests/reviews and help me finish
the software design with a good set of features.

Attached pictures from actually working & released product.

Regard

Jean-François

[Benta]

No thanks.
I've no interest in being an unpaid guinea-pig for your commercial product.
If you need testers, pay them.
Or do it like Microsoft: send out your product as is and let the users complain.

[TUMEMBER]

What do you expect from this test?
A review is a broad concept. Define its scope more precisely.
Specify more precisely "the method of device transfer, terms of use and return, and review deadline."
And don't be discouraged by "growling users"; some are demanding even when "the matter is of no interest to them or concerns them."
Is "someone who managed to install and put together the DAQ card on their own" enough? Is "someone who actively modifies the supplied software" necessary?


Try contacting HKJ
https://www.eevblog.com/forum/profile/?u=24271

[jfsimon]

Hi Tuemer,

Thank you,
Nothing special needed except applications/use cases
as the unit is functionning well an usable as a bench meter.

It can be programmed to Custom applications such as NTC Meter or
Strain Gauge display via Programmable functions.


It currently displays 4 channels real time,
I should implement Min/Miax/Filtered and Hold value before dispatch.
As well as as Logging (current value by pressing "V") and sampling/log.

These are part of the Windows app therefore should be swift to prepare.

Basically just using the instrument, if you have suggestions on applications,
i would take as well. Small modifications in the software and hook-up
wiring can do many type of applications for it.

We just came back with a Temperature Calibration tool for a 3D Printer
this morning. The apps can be custom and embedded in the software
to support these kind of use cases ...

I'm only interested in field experience and use cases ideas to
develop more software applications (inside the same Studio
we can embedded Applications that makes calculations/conversions
and logging, etc ...)

The unit's been otherwise
 - Calibrated
 - Tested
And is fully functional.

Regards

Jean-François

[TUMEMBER]

Hi Tuemer,


It can be programmed to Custom applications such as NTC Meter or
Strain Gauge display via Programmable functions.


if you have suggestions on applications,
i would take as well. Small modifications in the software and hook-up
wiring can do many type of applications for it.

We just came back with a Temperature Calibration tool for a 3D Printer
this morning.
The unit's been otherwise
 - Calibrated
 - Tested
And is fully functional.

Regards

Jean-François

So you need a "potential application area"? That's more your marketing side – a whole group of industrial applications with 0-10 V DC signal converters. After inserting a measuring resistor into the circuit, 4-20 mA converters are also possible. What fields can you "dream of?" besides the oil industry, because it doesn't look like it would be "explosion-proof."
Just a so-so final stage of control and measurement equipment, if not for really good "end-user friendly" software, then there is probably a much cheaper functional Chinese equivalent.
You haven't revealed any secret technical parameters, so there's essentially nothing to discuss – the number of digits after the decimal point is a poor indicator of measurement quality. The DAQ card I use can have up to 9 digits after the decimal point. What's the point if I can't read them without "stop" because they change so quickly? Only saving the data in logging mode gives me access to them.

Professional applications tend to target at least these cards, although research labs more often use products from the US National Instrument. Who's going to forbid a rich person? After all, they'll be throwing their money at the research and development department.

[jfsimon]

Hello,

This product does need some iterations but i want keep te design super simple, i don't want 24 bits 12 channels or something for this version.



The display goes slowly when values are stable (close from a multimeter) and rather fast in transients, but would need average and filtering, the application does not yet support these functions.

https://lecomptoirelectronique.fr/clv001_voltmeter

Regarding applications, i found out what was needed, that's gonna be a more long term evolution:
The software supports basic functions for the Voltage input and support custom functions through file modules which should be a math language.

Because i can write a couple apps but mostly we need to open/load them from the menus, someone wants signal supervision, someone wants a RTD conversion with a probe with B 3950 so on.

Therefore initially I wanted to implement them straight in source code but that won'd be good for future evolutions ...



4-Channel DC Voltmeter (0–30V)
USB-powered bench digital voltmeter designed to monitor multiple DC voltages simultaneously from a computer.

The CLV001 is a compact and affordable instrument ideal for electronics labs, prototyping, and monitoring power supplies or analog sensors.

Key Features
• 4 independent measurement channels
• 2 inputs: 0–10 VDC
• 2 inputs: 0–30 VDC
• Typical accuracy: ±1 %
• Input impedance: 1 MΩ
• Standard 4 mm banana connectors
• USB powered – no external power supply required

Free PC Application
The CLV001 connects through USB / serial to a free PC application providing:

• LED-style numeric display
• Real-time graphical display
• Min / Max / Average / Current values
• Data logging
• CSV export
• Threshold monitoring with audio alarm
• Configurable differential channels


Typical Applications
• Laboratory power supply monitoring
• Analog signal measurement (0–10 V sensors)
• Industrial sensor supervision
• Electronics testing and prototyping
• Simple data acquisition (DAQ)

Specifications

Parameter   Value
Number of channels   4
Input ranges   2 × 0–10 VDC / 2 × 0–30 VDC
Typical accuracy   ±1 %
Input impedance   1 MΩ
Power supply   USB
Interface   USB / Serial
Dimensions   145 × 90 × 45 mm
Weight   ~300 g


I can post a video of the product in use, basically, the AC is so far limited to 10 bits, I'm not in the high performance DAQ for that version of the products, it suits more the instrumentations of various types of sensors.

Regards

Jean-François

[moffy]

I have never seen that style of input connector before for the 4 chanels, would you mind saying what it is and maybe a link?

[NiHaoMike]

What's the maximum sample rate? I'm going to be mighty disappointed if it's not at least a few kHz, as a lot of microcontrollers will easily do more than that with 10 bits or more of resolution.

[jfsimon]

Good morning all,

I have never seen that style of input connector before for the 4 chanels, would you mind saying what it is and maybe a link?

The banana jacks are horizontal mount 4mm non safety style :
24.243.3
https://www.tme.eu/fr/details/pb4rt/prises-bananes-4mm/hirschmann-t-m/973582101
I want ideally update the Jacks and enclosure but that's what i use at the moment.

What's the maximum sample rate? I'm going to be mighty disappointed if it's not at least a few kHz, as a lot of microcontrollers will easily do more than that with 10 bits or more of resolution.

I did not exactly measure the sample rate, but it's going be in the kHz region indeed. The only compromize is about filtering, there is a bit of issues about cross channel coupling and noise when sampling at higher frequency so there need be fine tuning in there.
Ideally i don't want the LSB to fluctuate, there's at the moment a good algo that achieves that, it's slowing down the processing a bit and is working well.

Here are the atasheets released.


Datasheet (English)
https://micro-studioplc.com/clv001/clv001_ds.pdf
Datasheet (Español)
https://micro-studioplc.com/clv001/clv001_ds_es.pdf
Datasheet (Deutsch)
https://micro-studioplc.com/clv001/clv001_ds_de.pdf
Datasheet (Italian)
https://micro-studioplc.com/clv001/clv001_ds_it.pdf
Datasheet (Français)
https://micro-studioplc.com/clv001/clv001_ds_fr.pdf

Regards

Jean-François

[moffy]

The photo of the unit in your OP does not match the photo in the manual, they look computer generated not actual photos.

[inse]

Sorry for having to say so, but this is dull.
Only 10 Bits of resolution, low sample rate, fixed ranges, single ground terminal.
It does not allow stand alone data logging nor appears to provide galvanic isolation neither between the channels (though the manual suggests ‘independent‘) nor to the PC side.
I cannot figure out a use case for this device.
Even 12Bit scopes are hitting the hobby market now, how would you argument for your product?

[guenthert]

Sorry for having to say so, but this is dull.

Yeah, we didn't want to say it, but it's a bit underwhelming.

Only 10 Bits of resolution, low sample rate, fixed ranges, single ground terminal.
It does not allow stand alone data logging nor appears to provide galvanic isolation neither between the channels (though the manual suggests ‘independent‘) nor to the PC side.
I cannot figure out a use case for this device.
Even 12Bit scopes are hitting the hobby market now, how would you argument for your product?

I think the lack of galvanic isolation is the killer (hopefully not literally so).

It reminds me a bit of LabJack (TM).  Uh, I see they are still around.    Well, then ...

[tooki]

Yeah, it's unclear what the target market here really is. Other than the things below, and what others have mentioned, there's nothing wrong with it per se, but it's unclear what advantages it has over existing products.

10 bits really is kinda weak. I mean, that's what an Arduino Uno does. A TI INA226 chip that costs $3 gives you 16 bits, giving you over 36,000 counts on its 0-36V input, so ~1mV resolution, and in my testing, at 30 readings per second (120Hz sample rate and 4-sample averaging) it is within 3 counts -- so 3mv -- of my Keithley 2015 bench multimeter.) It can go much faster with reduced accuracy. TI makes other models (INA228 and INA229) with 20-bit resolution.

Input protection for industrial use needs to be robust.

I don't know why you'd choose non-safety banana jacks. Even if you don't need the protection (due to the limited input voltage range), it's just more convenient to be able to use whatever banana cables you have around, whether safety or not.

[jfsimon]

Hello,

That product serves mostly entry level at the moment, but can be used to display value in the units / scale so serve as a direct reading from sensors, temperature, force ...

I'm working on 2 modules, a teperature and straig gauge, to answer requsts, which are being supplied from the internal 10V reference.

The module will be connected to the input(s) and 10V supply of the device and display be customizable to show properly scaled 0-10V -> X-Y temperature or force.

It's a development tool but can act as good enough Voltage meter too, i just used it to monitor a PLC analog inputs, for that purpose it has enough accuracy and bits.

Inputs do have HV protection.
There is differential via software math between channels C1-C2 and C3-C4 possible (planned in future software updates).
Otherwise a very simple module that aims to be a DAQ-Like device when we don't need a full blown expensive unit. That's the idea so far.

Agree there are much more complex & industrialized specs possible, though would be for a very different variant of it, that one's hobby/entry level but as mentionned, can be used for lab's work.

I believe my employer uses 600€ dataloggers for temperature, which that unit can do well on 4 channels, provided i finalize and release the temperature converters.

So that's about all at this point, i got to release on a few DIY store and listen to much more complains, to consolidate a proper rev of this design.

If it branches to a more powerful/specialized/industrial DAQ then i would need onboard a small team, which i don't yet have.

Regards

Jean-François

[jfsimon]

The unit alows this kind of things, an definitely needs to get down the mV unit, a decade below.
Gonna set an update the Compute module in the works.

Also gonna implement the scale/offset, for example on this circuit we can read the MilliOhm directly
from the circuit, hence it's a mOhm meter once properly tuned.

What i really need to implement on this instrument is a way for users (like me) to make a custom application and load it. For instance in this case it needs:
- a button to set the Zero (on short circuit)
- a way to set scale so that Readings is in Milli-Ohm directly.

That way it can be tuned for about any value of components.
That's the idea, have this instrument Programmable in an easy way to make Custom applications, load them and use as needed.

Anyways back to the work bench.

Regards

Jean-François

[guenthert]

To expand on the galvanic isolation and to keep it constructive ...

Digilent's Analog Discovery doesn't offer galvanic isolation either.  They get away with it by implementing all the sources (PSU, signal generator) and sensors (DVM, oscilloscope, etc.) needed for beginners' circuits in one unit and targeting the educational market.

This "Laboratory power supply monitoring" (whatever might be meant by that -- after all, if I were to characterize a lab PSU I'd need much better than 10bit resolution and if I were suspecting a glitch, I'd be using a fast oscilloscope with differential or current probes, no?) threw me off.  Lab PSU are floating, so a ground referenced voltage logger would be severely limiting.

[jfsimon]

Got the points, datasheet's a bit incorrect, first i got to fix the ground issue.
Indeed not having a true hardware differential is an issue, ground brings
a lot of EMI, 80 mV noise and 200 mV events in my lab's observable.

Will see if this architecture can survice, though only if the device embeds a
solid power supply could it remain suitable for tested boards/parts.

I'll see if i keep both design, provied i got an arc that's reasonably cost
effective.

Regards
Jean-François

[temperance]

I wonder why you created such product. Multi channel loggers / meters are available from simple to very high accuracy and expensive from several vendors.

[jfsimon]

Hello Temperance,
Initially, i needed a combination of fairly good absolute accuracy (0.1-0.2%) over
a limited Voltage range (0-10V and 0-30V)
Needed accuracy in timing as well (about 5-10ppm) and programmable device that
can check over continuous pulses their duraction, and log the count number and
out of bands (eg 1s +/-10ms).

That's what i ended up using, has a 0.15% Voltage ref than is used to calibrated the
4 channels.

For more flexibility there are all 4 independant channels.

The unit as a Serial port that plugs to Serial/Programming device which is used for
serial com to the computer and used to reflash the controller every time i need tune
or add functions.

In the end what i did can take hours to check on a DAQ trace, ie check pulse durations
and make some sort of statistics.

I think it's possible with multiple high end equipment, which the lab used, but i did
equivalent things with a fairly simple device.

A 0.1% spec multimeter and a 1+k Daq's Job, provided the instruments are calibrated,
is the job i basically did.

I also put this device on the forefront to measure how many seconds it would hold in
fromnt of experienced engineers in here.

It was and still is basically use for my tests on programmable logic controllers during
R&D.

Permitted to find faults, but i admit the thing about it is it can be custom programmed,
that's what i really need and like, but not may be that useful to others so far.

That said i am upgrading the specs, i don't think my needs fit most others, but i want keep
that product evolving for a while, i still need here and there these functions.

Got a friend writing up calibration constants for C code on paper and tuning tempeature,
measuring with a cooking thermometer.
Not sure if many try these techniques, but with a few additions, that device can just make
it all.

Either it will be fully customized for a particular need as i do, or the default apps i can still
prepare would be not a too bad fit for similar works, both approaches work.

That's about for the genesis on that device.


Limitation of the 10 bits coming from the fact I manufactured 100pc of fully embedded and
nicely packed CH32V003 boards, and a 10 bit scale's almost good enough, but now i'll mod
by adding a proper DAC in between, and have the MCU talk to it.

Measured to 75 Hz max sample rate at 10 bits for the 4 channels with filtering at the moment,
that's not enough for what i plan, needs about 1kHz test device frequency and 10 kHz 16 bits
seems to be the right spec.

Just wondering if i keep floating or isolated channels, i'll be investigating more.
I still wouldn't want get too expensive unit in the end.

Regards

Jean-François

[temperance]

Have you seen this:

https://www.picotech.com/data-logger/adc-20-adc-24/precision-data-acquisition

[jfsimon]

Very cool product, never had chance to use on my side.
That's what i meant, in lab company i work for, they use similar devices.

I made a cheaper & more relevant to what i needed, but that's super nice.

I'm working on what ADC will use and proceed, but i don't have needs to match such crazy specs so far.
Further as you mentionned what would i need, instead i want customizable application, like a little bit similar to what labview can do, but a lot simpler, that's long term goal.

Device i build will have an API from software (running on computer) that can be connected via simple UDP socket and therefore build Python scripts and things like that to remotely control the device, perform some work and measurements.

Ideally that's where i really want and need to go.
I needed a physical platform to do that, first iteration's based on what i already had under hand, though taking inspirations from all this i'm in process to make something a bit more flexible.

Regards

Jean-François

[inse]

I salute for your perseverance, don’t get discouraged.
Bonne chance

[zapta]

Since the display is on a computer screen and is not limited to 7-segments, why not using a more readable font for the readings?

[jfsimon]

Thanks for input Zapta, i should as well have this as parameter, and few police available.
Mostly i selected this to be 7-segment-like but anything that's constant width should be working well.

Noted and put in todo

Regards

Jean-François

[tooki]

Got the points, datasheet's a bit incorrect, first i got to
fix the ground issue.
Indeed not having a true hardware differential is an
issue, ground brings
a lot of EMI, 80 mV noise and 200 mV events in my lab's
observable.

Will see if this architecture can survice, though only if
the device embeds a
solid power supply could it remain suitable for tested
boards/parts.

I'll see if i keep both design, provied i got an arc that's
reasonably cost
effective.

Regards
Jean-François

Just a little request: please don't put in line breaks at the end of each line. It's the browser's job to do that so that lines break according to the user's screen/window size. Just put in line breaks to separate paragraphs.

(Extra line breaks get super annoying when viewing on a phone, where you often have a narrow screen width, causing your lines to break anyway, and then the manual line breaks come anyway. I simulated the effect in the quote of your text above.)