Author Topic: project: extending HP3478A functionality  (Read 12530 times)

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Offline kirill_ka

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project: extending HP3478A functionality
« on: August 11, 2017, 08:59:00 am »
HP3478A considered to be a good multimeter, but lacks some basic functions expected from current models (e.g. relative, auto hold, average).
What I'm thinking to do is to hook up microcontroller to GPIB bus internally so it will provide additional functions.
I already have some idea what the "user interface" would look like. Display and SRQ button are available via GPIB. "Local" button is also available indirectly.
That should be enough to implement basic menu system.
...
Update (January 30, 2018): working prototype is ready
The hardware is very basic. To reproduce it you'll need the following stuff:
github project: https://github.com/KIrill-ka/hp3478ext

Functions already implemented:
  • USB interface - allows to execute generic GPIB commands
  • relative mode
  • xohm mode - measure resistances above 30M
  • continuity tester
  • min max
  • diode tester*
  • auto hold
  • temperature**
What else can be done:
  • running average
* Not sure if I want one. It's just a 2w \$\Omega\$ in 3K range. However, beeping may be added.
** Limited to one particular RTD sensor.


Update (September 3, 2018):
The thing now leaves inside my HP3478A powered from it's internal supply. The only hardware modification I had to do to the HP3478A was a cut-out for USB TypeB socket.
This process of integration to the HP3478A is not documented yet (TODO), but now there's a guide for basic implementation and a command reference.
The links are on the project homepage: https://kirill-ka.github.io/hp3478ext/
Thanks to bitseeker for carefully reviewing the documentation.
hp3478ext allows to send generic GPIB commands to a device, so it can be used as a cheap GPIB-USB adapter. For instance, I'm using it with my HP8561E. I wrote a Tcl library implementing some GPIB functions, which I'm going to release very soon.
« Last Edit: September 03, 2018, 12:41:29 pm by kirill_ka »
 
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Online alm

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Re: project: extending HP3478A functionality
« Reply #1 on: August 11, 2017, 12:29:05 pm »
How would you do the UI? Talking to it will lock out all front panel keys except local. You could send GTL after every command, but how do you detect button presses other than SRQ? Morse code with SRQ? How do you know if the meter switches range or function? What would the display update rate be like?
 

Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #2 on: August 11, 2017, 12:54:52 pm »
How would you do the UI? Talking to it will lock out all front panel keys except local. You could send GTL after every command, but how do you detect button presses other than SRQ?
If you press "Local" it stops responding to commands. I found a trick which makes it possible to know that it doesn't respond without entering LISTEN state.
So I should be able to detect two buttons SRQ and Local.
S.Trig and then SRQ can turn on "relative" mode directly.
How do you know if the meter switches range or function? What would the display update rate be like?
Current mode is available in status bytes (B command).
If "additional" functions are not activated, 3478 should stay in normal (local) mode until SRQ is pressed.
What would the display update rate be like?
I don't know. We'll see. When I tried to enter commands manually it seemed to be quick enough.
 

Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #3 on: August 11, 2017, 01:02:58 pm »
Morse code with SRQ?
It's also possible to sniff keypad lines directly, but I prefer it to be GPIB-only.
 

Online alm

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Re: project: extending HP3478A functionality
« Reply #4 on: August 11, 2017, 01:29:08 pm »
I agree that something that just plugs into the GPIB connector would be much neater. The challenge will be good integration with normal operation without jarring mode switches. Good luck!
 
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Offline macboy

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Re: project: extending HP3478A functionality
« Reply #5 on: August 11, 2017, 03:57:02 pm »
I did something similar for Keithley 199 years ago. For that meter, it was possible to have a GPIB SRQ generated whenever a front panel button was pressed. The meter would not otherwise respond to front panel buttons (since it was in remote mode). The software could then query which key was pressed and take whatever action was needed, including changing mode or range on the meter. The software-generated/modified reading including units could be sent to the meter's display using a special GPIB command. The 3478A has a similar 14-segment alpha-numeric display, and a very similar command set, but it doesn't seem to have the ability to pass through the keypresses to the GPIB controller in the same way.
Anyway, good luck.
 
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Offline pigrew

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Re: project: extending HP3478A functionality
« Reply #6 on: August 11, 2017, 05:04:43 pm »
Personally, the features I'd want to see would involve ripping out the microcontrollers and analog components and replacing them with something newer, though I'm really not sure if it's worth it.

I personally use GPIB to communicate with it, so I

For example:
  • Replace A/D controller with a modern micro, to get more digits by running at a higher clock speed (I'm not sure if the noise would improve, though)
  • Replace main controller to use a modern micro's internal flash RAM (to avoid the need for the calibration-RAM battery)
  • Replace integrator IC with lower-noise op-amp?
  • Replace main input amplifier? A don't know what the existing part is.

But, would those things be worth it? If replacing an IC or two helps, great, but once I start thinking about replacing micros, the cost might expand to be more than the price of a 6.5 digit DMM.

For some of the digital things mentioned, it sounds like changing the display is required (for example to display averaged data). For this, I believe that the main micro would need to be replaced. Though, the programming shouldn't be too hard and it would be neat to end up with an instrument with open-source firmware.
 

Offline agaelema

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Re: project: extending HP3478A functionality
« Reply #7 on: August 21, 2017, 02:12:48 am »
Some time ago I was thinking about it when I was searching about DIY GPIB interface to connect my 3478A to computer without need to spend lots of money (more than the DMM price) in an adapter.

But from what I've read, when the DMM remote mode is activated it stops responding locally. Right?

In my opinion, I do not see problems using remote controls (buttons) and another screen, in fact I think they can bring some advantages, a separate screen would be very interesting in allow more measurements at same time, like std value, min, max, etc...

You know some good GPIB DIY project, I think that this is the start of all.
 

Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #8 on: August 23, 2017, 01:55:42 pm »
Some time ago I was thinking about it when I was searching about DIY GPIB interface to connect my 3478A to computer without need to spend lots of money (more than the DMM price) in an adapter.

But from what I've read, when the DMM remote mode is activated it stops responding locally. Right?
Not exactly. There's no single thing called "DMM remote  mode". GPIB remote mode is required to send a command, where only SRQ and Local keys are active. But after that, local control might be restored.
In my opinion, I do not see problems using remote controls (buttons) and another screen, in fact I think they can bring some advantages, a separate screen would be very interesting in allow more measurements at same time, like std value, min, max, etc...
The objective is to use hp3478 as a standalone DMM. And I don't want to make many hardware modifications. I have to respect 30+ years old instrument after all :)
You know some good GPIB DIY project, I think that this is the start of all.
I started with this:
https://github.com/JacekGreniger/gpib-converter
Although, I already re-wrote most of the code.
 

Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #9 on: August 23, 2017, 02:00:48 pm »
Personally, the features I'd want to see would involve ripping out the microcontrollers and analog components and replacing them with something newer, though I'm really not sure if it's worth it.
What would be left in there?
 

Offline pigrew

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Re: project: extending HP3478A functionality
« Reply #10 on: August 23, 2017, 02:12:47 pm »
Personally, the features I'd want to see would involve ripping out the microcontrollers and analog components and replacing them with something newer, though I'm really not sure if it's worth it.
What would be left in there?
I wouldn't mess with most of the analog circuitry (other than substituting ICs). The integrating ADC controller would remain, as would voltage references and precision resistors. The power supply seems fine, and I'm happy with the front panel. The chassis, switching relays, input terminals, fuses, etc. are likely not limiting performance either.

I was imagining how US$50 parts could best be spent on upgrading the unit.
 

Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #11 on: August 24, 2017, 12:40:05 pm »
I've opened a github repository.
https://github.com/KIrill-ka/hp3478ext
My prototype is atmega328 board (arduino nano) which is directly connected to GPIB. And usb-uart dongle is on the other side.
Relative mode is already working. It's entered by pressing S.Trig then SRQ.
It also works as interactive GPIB-UART interface. Someone may find it useful not only for HP3478.
 
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Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #12 on: August 30, 2017, 02:13:40 pm »

Testing extended Ohms mode: 5x68 MOhm resistors.
« Last Edit: August 30, 2017, 02:27:27 pm by kirill_ka »
 

Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #13 on: August 30, 2017, 02:23:25 pm »
What would the display update rate be like?
I don't know. We'll see. When I tried to enter commands manually it seemed to be quick enough.
In 4 digit relative mode the display update appears to be much faster than you normally get from HP3478A. Possibly it's intentionally limited to make the display readable. I'm not sure if I want to do the same.
 

Offline bitseeker

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Re: project: extending HP3478A functionality
« Reply #14 on: August 31, 2017, 12:34:00 am »
Cool project, kirill. I've thought about extending the functionality of DMMs and power supplies via GPIB, too. Adding a second display for stats, logging, and graphs would be quite an upgrade for the good ol' 3478A.
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Online alm

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Re: project: extending HP3478A functionality
« Reply #15 on: August 31, 2017, 06:02:52 am »
You can experiment. But especially on that old LCD increasing the update rate may not help readability. Try observing a value quickly fluctuating between 6 and 7. If you had some way of doing an analog bar graph, a higher update rate might be valuable. Same with any logging or plotting.
 

Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #16 on: August 31, 2017, 08:49:34 am »
You can experiment. But especially on that old LCD increasing the update rate may not help readability. Try observing a value quickly fluctuating between 6 and 7. If you had some way of doing an analog bar graph, a higher update rate might be valuable. Same with any logging or plotting.
I've measured actual reading rate and it's not the same as display update. HP3478 has two commands D2 and D3. D2 seems to be buffered, so the display is not updated every time. D3 is  like it writes the LCD immediately. And the more often you write the screen, the less reading rate you get. The maximum I could get so far is 75 reading/sec in 3 digit mode with auto zero off.
 

Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #17 on: August 31, 2017, 09:12:10 am »
Cool project, kirill. I've thought about extending the functionality of DMMs and power supplies via GPIB, too. Adding a second display for stats, logging, and graphs would be quite an upgrade for the good ol' 3478A.
Thank you for support! I'm thinking to mount atmega328 inside, and stick out an usb or uart connector. Then raspberry pi can be added for logging and graphing.
 

Offline bitseeker

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Re: project: extending HP3478A functionality
« Reply #18 on: August 31, 2017, 05:38:35 pm »
That sounds cool. I'm following the thread. :-+
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Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #19 on: September 05, 2017, 02:24:42 pm »
UI scheme
« Last Edit: September 05, 2017, 02:27:11 pm by kirill_ka »
 

Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #20 on: September 29, 2017, 10:14:09 am »
Next (kind of) prototype is ready! Now it's fitted inside the case. I'll add usb type B port to the back when the cable arrives.
The software part works quite well. So I'm going to use it for some time to see what I want do next.
 

Offline dom0

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Re: project: extending HP3478A functionality
« Reply #21 on: September 30, 2017, 02:12:25 pm »
Personally, the features I'd want to see would involve ripping out the microcontrollers and analog components and replacing them with something newer, though I'm really not sure if it's worth it.
What would be left in there?
I wouldn't mess with most of the analog circuitry (other than substituting ICs). The integrating ADC controller would remain, as would voltage references and precision resistors. The power supply seems fine, and I'm happy with the front panel. The chassis, switching relays, input terminals, fuses, etc. are likely not limiting performance either.

I was imagining how US$50 parts could best be spent on upgrading the unit.

I wouldn't mess with most of the analog circuitry (other than substituting ICs)
That's kinda an oxymoron, isn't it? The circuit was designed for a specific IC, swapping random ICs makes it a different circuit, behaving differently, not required to behaver better.

In the 3478A many important components are not changed easily, anyway. For example, most of the input switching and protection is on a hybrid in the input section (it also contains some relay drivers, a questionable combination in my mind). This will probably make attempts to reduce input currents futile, for example.

If memory serves, they mainly used a selection of LM308s, LF412s and OP07s to implement the various circuits. The main input amp iirc was a HP P/N part, might be selected/treated off the shelf, might be custom.
,
 

Offline alterbaron

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Re: project: extending HP3478A functionality
« Reply #22 on: September 30, 2017, 04:39:08 pm »
Super cool project!

BTW, you may want to replace this cap.



I've had caps like that fail and leak nasty stuff all over the board. IIRC they're known for doing that.
 
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Offline Rbastler

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Re: project: extending HP3478A functionality
« Reply #23 on: September 30, 2017, 04:46:01 pm »
Super cool project!

BTW, you may want to replace this cap.



I've had caps like that fail and leak nasty stuff all over the board. IIRC they're known for doing that.

Jep, one blew in my Philips supply while testing it. Evil things.
http://rbastlerblog.jimdo.com/
Gamma spectrometer works. Now some yellow crystals need regenerating and testing.
 

Offline bitseeker

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Re: project: extending HP3478A functionality
« Reply #24 on: September 30, 2017, 07:04:54 pm »
BTW, you may want to replace this cap.



I've had caps like that fail and leak nasty stuff all over the board. IIRC they're known for doing that.

Yes! Rifa caps fail spectacularly, often to the detriment of neighboring components. Definitely change old ones, especially if the clear/translucent outer shell is exhibiting stress fractures, like the one in the photo, above.
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Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #25 on: October 01, 2017, 10:45:40 am »
BTW, you may want to replace this cap.
I've had caps like that fail and leak nasty stuff all over the board. IIRC they're known for doing that.
Thank you. I will definitely replace it. I didn't think they are so badly behaved.
 

Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #26 on: January 29, 2018, 09:01:51 pm »
 
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Offline The Soulman

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Re: project: extending HP3478A functionality
« Reply #27 on: January 29, 2018, 10:09:19 pm »
 :-+ Now you should write a new manual for it.  :P
Well done.
 

Offline babysitter

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Re: project: extending HP3478A functionality
« Reply #28 on: January 30, 2018, 08:24:07 am »
Thank you for pointing out this little bugger. After having 2 machines blowing their tar last year, I am in the process of exchanging all RIFAs I find. 2 Devices are clear now, with the 3478A its 3 waiting now.
I'm not a feature, I'm a bug! ARC DG3HDA
 

Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #29 on: January 30, 2018, 09:32:03 am »
Thank you for pointing out this little bugger.
There are 4 of them. I think 2 big ones (0.022uF) are not that dangerous, because they are connected across the switch.
But the other two 1000pF are across mains.
 

Offline kelchm

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Re: project: extending HP3478A functionality
« Reply #30 on: February 06, 2018, 11:45:02 pm »
There are 4 of them. I think 2 big ones (0.022uF) are not that dangerous, because they are connected across the switch.
But the other two 1000pF are across mains.
Are you maybe thinking of another meter? I just took a look at my notes from when I tore down my two 3478A's and I didn't note down seeing any 1000pF caps. Did I miss something?

Here's what I noted down as caps that I will replace eventually:

S/N 2619A48043
LocationCapacitanceVoltageBrandNotes / Other Markings
C7613300µF25VSMC8827(2) (M)85ºC
C702330µF50VSMC88 C(2) (M)85ºC
C703330µF50VSMC88 C(2) (M)85ºC
C7111000µF25VSMC8835(2) (M)85ºC
C7650.022µF250VRIFAPhoto
C7660.022µF250VRIFASee Above

S/N 2619A39329
LocationCapacitanceVoltageBrandNotes / Other Markings
C7613300µF25VSMC8827(2) (M)85ºC
C702330µF50VSprague8742(M) 85ºC
C703330µF50VSprague8742(M) 85ºC
C7111000µF25VSMC8831(2) (M)85ºC
C7650.022µF250VRIFAPhoto
C7660.022µF250VRIFASee Above
 

Offline kelchm

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Re: project: extending HP3478A functionality
« Reply #31 on: February 06, 2018, 11:50:00 pm »
A quick video demonstration.
 
https://drive.google.com/open?id=179wN6CET8ZQY1wQDYIMmN7-N4oslAw8C
This is awesome!

I've starred your repository and plan on experimenting with this at some point in the future.
 

Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #32 on: February 07, 2018, 09:31:22 am »
Are you maybe thinking of another meter? I just took a look at my notes from when I tore down my two 3478A's and I didn't note down seeing any 1000pF caps. Did I miss something?
Those are A1C721 and A1C720. I have an old version of 3478A. Maybe they where changed in newer revisions.
 

Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #33 on: February 07, 2018, 09:34:24 am »
I've starred your repository and plan on experimenting with this at some point in the future.
You are welcome :)
 

Offline kelchm

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Re: project: extending HP3478A functionality
« Reply #34 on: February 07, 2018, 10:21:28 pm »
Are you maybe thinking of another meter? I just took a look at my notes from when I tore down my two 3478A's and I didn't note down seeing any 1000pF caps. Did I miss something?
Those are A1C721 and A1C720. I have an old version of 3478A. Maybe they where changed in newer revisions.
Thanks, I took another look and was able to locate them. They are directly between the transformer and the mains input. Removing the GPIB ribbon cable makes them easier to see.

 

Offline bitseeker

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Re: project: extending HP3478A functionality
« Reply #35 on: February 07, 2018, 11:03:43 pm »
Thanks for the photo. I should check that, too.
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Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #36 on: July 18, 2018, 02:54:50 pm »
The software part works quite well. So I'm going to use it for some time to see what I want do next.
I've been using my "extended" HP3478 for awhile now. All the features work very well.  Now I'm asking for an advice on what else to do about this project. Probably I should add some documentation to make it easy to reproduce? I feel a bit uncomfortable about I'm the only one using such a cool thing :)
 
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Offline bitseeker

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Re: project: extending HP3478A functionality
« Reply #37 on: July 18, 2018, 04:49:31 pm »
Implementation and operation guides so others could build and operate it would certainly be good things to have to make a more complete package. :-+
I TEA.
 
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Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #38 on: August 21, 2018, 09:37:35 am »
At last there is some progress with the documentation. Since I've been experimenting with HP8561e, I revised GPIB command line and wrote a command line reference.
https://kirill-ka.github.io/hp3478ext/
Also there's a basic implementation guide, and pre-compiled firmware.
Any suggestions, comments are very welcome.  I'm not comfortable writing manuals in English, so the text is probably awkward. I would be happy if someone help me to improve it.
 

Offline bitseeker

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Re: project: extending HP3478A functionality
« Reply #39 on: August 22, 2018, 02:33:05 am »
Thanks kirill. Can you send me the LibreOffice Writer files? It's more efficient making corrections that way rather than have you re-enter them from a list of changes.
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Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #40 on: August 22, 2018, 05:31:21 am »
Thanks kirill. Can you send me the LibreOffice Writer files? It's more efficient making corrections that way rather than have you re-enter them from a list of changes.
I just uploaded them to the git. Thanks.
https://github.com/KIrill-ka/hp3478ext/blob/master/ug1-gpib-commands.odt?raw=true
https://github.com/KIrill-ka/hp3478ext/blob/master/ig1-basic.odt?raw=true
 

Offline bitseeker

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Re: project: extending HP3478A functionality
« Reply #41 on: August 22, 2018, 06:33:13 pm »
Pull request submitted. I clicked a bit too fast and may have borked it. Let me know.
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Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #42 on: August 25, 2018, 06:29:18 pm »
Pull request submitted. I clicked a bit too fast and may have borked it. Let me know.
bitseeker, thank you for spending your time on this. It's a very valuable experience to me.  I had to revert some spacing changes, because html and odt don't look the same. If you add empty lines in odt to make it better, html becomes too sparse. Tabs also behave differently.
 

Offline bitseeker

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Re: project: extending HP3478A functionality
« Reply #43 on: August 25, 2018, 07:11:12 pm »
Ah, OK. I should've checked that. :palm: I haven't used word processors for HTML, so I only paid attention to the way it looked in its native form. I hope it wasn't too much of a hassle to revert the spacing. I enabled tracking for all the edits in the hopes it would minimize the effort to remove any changes that you didn't want.

Once you're done with any additional info for the docs, I can take a final pass over the text (I'll leave the spacing alone).
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Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #44 on: August 27, 2018, 11:04:16 am »
I think I'm done with it for now. So, you are welcome to take a look.  I tried to clarify the description of the OX command and added a small section on the stand-alone HP3478A operation. There should be no changes apart from that.

Meanwhile I wrote a basic Tcl library for remote programming. I'll publish it and also some Tk GUI examples as soon as I have enough play with it.
 

Offline bitseeker

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Re: project: extending HP3478A functionality
« Reply #45 on: August 29, 2018, 12:16:34 am »
OK, I'll check it out when I get home.
I TEA.
 

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Re: project: extending HP3478A functionality
« Reply #46 on: August 29, 2018, 03:49:27 am »
That new paragraph describing the standalone extension mode helps a lot. I just made a few corrections to touch it up and created a pull request for you.

Cheers!
I TEA.
 
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Re: project: extending HP3478A functionality
« Reply #47 on: December 28, 2018, 08:01:54 pm »
Hi Kirill,

I tried your project on my HP3478A and it doesn't do anything when I press SRQ. Can you check the fuses configuration on the Atmega? I've checked the connections twice.

Thanks,
Miti

Edit: I'm not using the USB to serial adapter. I understand that part is optional if you want to send commands to the meter, or am I missing something? Should it work only with the mini pro?
« Last Edit: December 28, 2018, 08:09:02 pm by Miti »
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Re: project: extending HP3478A functionality
« Reply #48 on: December 28, 2018, 09:28:55 pm »
Hi Miti,

It definitely works without an USB-to-UART adapter, but it would be very hard to diagnose any problems without one.
How did you download the firmware then?
The "standard" fuse settings used on those atmega328p boards should work.
However the recommended efuse configuration is at the bottom of the following page:
https://kirill-ka.github.io/hp3478ext/basic-impl.html
« Last Edit: December 28, 2018, 09:39:35 pm by kirill_ka »
 

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Re: project: extending HP3478A functionality
« Reply #49 on: December 28, 2018, 09:51:33 pm »
I tried your project on my HP3478A and it doesn't do anything when I press SRQ.
I just checked the source... The SRQ key is disabled by default, so you either need to program the provided eep file or enable it with OX1w serial command.
 

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Re: project: extending HP3478A functionality
« Reply #50 on: December 28, 2018, 10:32:04 pm »
Hi Miti,

It definitely works without an USB-to-UART adapter, but it would be very hard to diagnose any problems without one.
How did you download the firmware then?
The "standard" fuse settings used on those atmega328p boards should work.
However the recommended efuse configuration is at the bottom of the following page:
https://kirill-ka.github.io/hp3478ext/basic-impl.html

I programmed using USB-AVR-ISP. Both main flash and EEP pass verification.

Edit: I have a feeling that the Arduino bootloader is still needed. However, it was erased when I programmed it using the ISP programmer. Could that be the cause?
« Last Edit: December 28, 2018, 10:42:24 pm by Miti »
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Re: project: extending HP3478A functionality
« Reply #51 on: December 29, 2018, 07:12:38 am »
Could that be the cause?
Yes. Then you need  to disable the bootloader with fuse bits...
 

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Re: project: extending HP3478A functionality
« Reply #52 on: December 29, 2018, 05:20:54 pm »
I did but it still doesn't work. See attached screen shots for flash and EEP verification and the fuses status.
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Re: project: extending HP3478A functionality
« Reply #53 on: December 29, 2018, 06:26:41 pm »
I'm almost out of ideas what can we try without the serial interface.
What's the GPIB address of HP3478A? Is it set to default?
You may try to set PWR ON SRQ DIP switch to see if SRQ annunciator is cleared after power off.
Do you see LSN or TLK annunciators blinking after powering 3478A on?

I'll check fuse config later, but your setting looks right.
 

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Re: project: extending HP3478A functionality
« Reply #54 on: December 29, 2018, 06:44:12 pm »

What's the GPIB address of HP3478A? Is it set to default?
You may try to set PWR ON SRQ DIP switch to see if SRQ annunciator is cleared after power off.
Do you see LSN or TLK annunciators blinking after powering 3478A on?

I'll check fuse config later, but your setting looks right.

The GPIB address was set to 2. I set it to 0 and still nothing. What should it be? I set the PWR ON SRQ and SRQ is displayed and stays there.
LSN and TLK never blink.
« Last Edit: December 29, 2018, 06:49:35 pm by Miti »
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Re: project: extending HP3478A functionality
« Reply #55 on: December 29, 2018, 06:52:07 pm »
The GPIB address was set to 2. I set it to 0 and still nothing. What should it be? I set the PWR ON SRQ and SQR is displayed and stays there.
LSN and TLK never blink.
The default address for HP3478A is 23.
 

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Re: project: extending HP3478A functionality
« Reply #56 on: December 29, 2018, 07:00:50 pm »
 :-+

That was it, the address was wrong. You should add that to the instructions. Thanks a lot Kirill!
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Re: project: extending HP3478A functionality
« Reply #57 on: December 29, 2018, 07:46:14 pm »
That was it, the address was wrong. You should add that to the instructions.
Yes, I will.  I'm glad you got it working.
Power on SRQ is also recommended setting, since it helps to detect 3478A's reset condition.
« Last Edit: December 29, 2018, 09:59:02 pm by kirill_ka »
 
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Re: project: extending HP3478A functionality
« Reply #58 on: December 29, 2018, 10:16:14 pm »
I like your project! I think I'll put it on a proper PCB and install it in my two meters.  :clap:  :-+

Edit: Is the UI diagram in page one up to date? Mine doesn't seem to follow it or I don't understand it.
« Last Edit: December 29, 2018, 10:50:20 pm by Miti »
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Re: project: extending HP3478A functionality
« Reply #59 on: December 31, 2018, 08:17:21 am »
Edit: Is the UI diagram in page one up to date? Mine doesn't seem to follow it or I don't understand it.
Autohold, diode and temperature functions are missing from it. Other than that, it seems to be correct.
The (SRQ)) thing means that you have to press SRQ number of times. The particular order of menu entries is not shown.
Also note, that autohold seems to work better in 4 digit mode.
 

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Re: project: extending HP3478A functionality
« Reply #60 on: December 31, 2018, 08:25:39 am »
I think I'll put it on a proper PCB and install it in my two meters.
Then I owe you to describe how I connected the UART-USB module...
 

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Re: project: extending HP3478A functionality
« Reply #61 on: December 31, 2018, 12:56:05 pm »
Then I owe you to describe how I connected the UART-USB module...

That won't be necessary, I think I know how to connect them. I will send you the schematic for validation before I do the layout. I have couple of questions though:
1. In one of your pictures you connect the GPIB on top of the add-on module. Can you have it both ways, add this extra functionality, the USB and have the GPIB functional as well? Do you put everything in tri-state? I don't think that can be done.
2. What's the PWM frequency of the buzzer? It seems to be a bit low for the buzzer that I have. They work best close to their resonant frequency, did you have a specific part in mind when you selected that frequency?
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Re: project: extending HP3478A functionality
« Reply #62 on: December 31, 2018, 04:23:19 pm »
I pulled up TX pin of CP2101 to it's internal 3.3V regulator and connected to 328p's RX through a diode. USB 5V is also connected to 328p through a Shottky diode. So the CP2101 is not powered through the arduino board.
I used unregulated 5V supply (which is more like 15V) to power the arduino board to use it's diode, fuse, and internal regulator.

1. It should be fine if you disable 3478A extensions (OX0 command). Most* GPIB lines are not actively pulled high in atmega. I assume 2 scenarios:
1) external USB controller is used, then atmega board does nothing.
2) hp3478ext can be used as a controller for other devices connected to HP3478A externally.
Although, in both cases GPIB signals should stay within allowed atmega pin voltage.
* I should check the code, and tell you how it works exactly. May be I haven't put enough thought in it...

2. If it's a buzzer, it doesn't require PWM. Initially I used piezo speaker (which requires a driver to sound properly). When I switched to the buzzer, I left pwm so the buzzer doesn't sound loud. I can add eerpom config to it so you can tweak it.

UPDATE:
IEEE 488 specifies maximum signal level as 5.25V. This should be fine for AVR.
All GPIB signal lines in hp3478ext are driven in open collector way. There's no strong pull up.
DAV and SRQ lines are weakly pulled up. Current hp3478ext firmware pulls DIO low when inactive. I'm going to remove this behaviour, because it would conflict with an external GPIB controller.
« Last Edit: January 01, 2019, 03:48:17 pm by kirill_ka »
 

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Re: project: extending HP3478A functionality
« Reply #63 on: January 01, 2019, 09:46:32 pm »
I got bored today and put together a schematic.
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Re: project: extending HP3478A functionality
« Reply #64 on: January 02, 2019, 07:19:53 pm »
I got bored today and put together a schematic.
It looks good. Thanks.
Please, consider the modifications I made.
J3: 2.54mm pitch connector for USB B socket (which can be mounted on the back of 3478A).
 

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Re: project: extending HP3478A functionality
« Reply #65 on: January 05, 2019, 05:04:28 pm »
Hi Kirill,

I have a couple of questions:

1. What's the benefit of powering the FT232 from USB only? It is held in reset while USB is not plugged anyway and I save three diodes.
2. What's D6 doing? Is it a heart beat indicator?

Thanks,
Miti
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Re: project: extending HP3478A functionality
« Reply #66 on: January 05, 2019, 05:15:05 pm »
D6 could be an heart beat, activity monitor etc ..  it depends on the firmware coding, i dont think the ft232 would be held in reset,  i have FTDI usb adapters always connected to my pc,  until you open connection on com ports, they stand still and are waiting ?? and the coms on the "slave" interfaces are not held in reset too, they function normally.

I have FTDI usb-rs232, but hey have an added buffer bidirectional i/o chip inside.  We did had problems of isolation / data lines not pulled correctly and when i made some tests it affected the "slave" instruments circuits.

Not sure the ft232 would have some isolation ?? You may end with ground problems if you take some measurements with the meter and be connected to an computer.

Thats why i push some good isolation circuit for the usb-gpib interface ??  I know, i know  its not a 5$ dongle, but when you measure voltage potential between pc ground and interface grounds you may have some surprise(s).

I would have added an small dc-dc 5 volts converter isolator, they have a very small footprint, it would add more isolation, but not on the data signals.

Is the Official HP Agilent  usb-gpib   has known available schematics ??  since we have so many cloned devices from china.

Usb isolator:  9$ usd
https://www.ebay.com/itm/1500V-USB-to-USB-Isolator-Board-Protection-Isolation-ADUM4160-ADUM3160-Module/152382773951?hash=item237ab89abf:g:2d8AAOSwEzxYbQMG:rk:2:pf:0
« Last Edit: January 05, 2019, 05:31:54 pm by coromonadalix »
 

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Re: project: extending HP3478A functionality
« Reply #67 on: January 05, 2019, 09:24:25 pm »
Hi Miti.
1. What's the benefit of powering the FT232 from USB only? It is held in reset while USB is not plugged anyway and I save three diodes.
The idea is to allow the whole thing to be USB powered.
a) for testing purposes
b) for external GPIB connection
c) to allow firmware updates while the 3478A is turned off
Anyway, you can leave pcb jumpers and leave those components unpopulated.
2. What's D6 doing? Is it a heart beat indicator?
Current firmware blinks it when it's in the GPIB listen state.
It can be repurposed for something... Heart beat may be a better use for it. So you know the firmware is alive.
 

Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #68 on: January 05, 2019, 09:32:18 pm »
Not sure the ft232 would have some isolation ?? You may end with ground problems if you take some measurements with the meter and be connected to an computer.
Digital part of HP3478A is already isolated from analogue part. I don't see why the USB isolation would be necessary.
 

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Re: project: extending HP3478A functionality
« Reply #69 on: January 05, 2019, 10:00:51 pm »
... i dont think the ft232 would be held in reset,  i have FTDI usb adapters always connected to my pc,  until you open connection on com ports, they stand still and are waiting ?? and the coms on the "slave" interfaces are not held in reset too, they function normally.

Read section 6.2 in the attached datasheet.

I have FTDI usb-rs232, but hey have an added buffer bidirectional i/o chip inside.  We did had problems of isolation / data lines not pulled correctly and when i made some tests it affected the "slave" instruments circuits.

Not sure the ft232 would have some isolation ?? You may end with ground problems if you take some measurements with the meter and be connected to an computer.

Thats why i push some good isolation circuit for the usb-gpib interface ??  I know, i know  its not a 5$ dongle, but when you measure voltage potential between pc ground and interface grounds you may have some surprise(s).

I would have added an small dc-dc 5 volts converter isolator, they have a very small footprint, it would add more isolation, but not on the data signals.

Is the Official HP Agilent  usb-gpib   has known available schematics ??  since we have so many cloned devices from china.

Usb isolator:  9$ usd
https://www.ebay.com/itm/1500V-USB-to-USB-Isolator-Board-Protection-Isolation-ADUM4160-ADUM3160-Module/152382773951?hash=item237ab89abf:g:2d8AAOSwEzxYbQMG:rk:2:pf:0

Take a look at the block diagram in the service manual of HP3478A. The meter has two sections, the analog, measuring section and the digital, processing, displaying, communication section. These two sections are galvanically isolated. The two sections are present in all bench meters and they are called chassis common/floating common in this particular HP meter, inguard/outguard in Fluke meters. The data transfer between sections is done through transformers or optocouplers. Unless you do something (stupid, maybe dangerous and, in case of bench meters, useless) to isolate the chassis from the ground (earth), the meter chassis and the PC chassis that is connected to, should be at the same level, ground level. The measurements should not be affected at all.
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Re: project: extending HP3478A functionality
« Reply #70 on: January 06, 2019, 03:17:39 am »
Sorry

I forgot the meter circuit ingard outgard circuit(s),  disregard my comments,  same for my 34401a   loll    :palm:
 

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Re: project: extending HP3478A functionality
« Reply #71 on: February 17, 2019, 02:56:46 am »
And here's the board. Populated, tested. Tomorrow I will take some pictures inside the meter.

Kirill,

Is the source code Arduino or C? Could you share it?

Edit: Added picture inside the meter.
Edit1: Never mind, brain fart, the code is on github.
« Last Edit: February 17, 2019, 02:56:18 pm by Miti »
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Re: project: extending HP3478A functionality
« Reply #72 on: February 17, 2019, 05:58:20 pm »
Great news! Thanks. I see you found a proper socket with long pins. I used pin headers meant for Arduino shields. They didn't fit well.
 

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Re: project: extending HP3478A functionality
« Reply #73 on: February 17, 2019, 07:02:32 pm »
This is how I installed USB type B socket for remote control and programming.
I used a cable like that:
https://www.ebay.com/itm/2pcs-90-Degree-Left-Right-Angled-USB-B-Type-Male-to-Female-Extension-Cable/262054119211

EDIT: it's a fail! The socket can't be used while GPIB cable is plugged. It should be moved further away from the GPIB connector.
« Last Edit: February 22, 2019, 09:53:39 pm by kirill_ka »
 

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Re: project: extending HP3478A functionality
« Reply #74 on: February 17, 2019, 09:15:38 pm »
Great news! Thanks. I see you found a proper socket with long pins. I used pin headers meant for Arduino shields. They didn't fit well.

Lool!

That's exactly what I used, the pins from an Arduino stackable header kit on the bottom and a socket on the top. Pretty hard to keep together and solder...and that kit is damn expensive.
The problem with the sockets with long pins is that they are square and pretty thick. One insertion would damage the socket on the meter. I couldn't find a socket with long, flat pins.

Edit: It doesn't work with external GPIB adapter in parallel with the extension for me. You may want to look at the code and see if all the lines are high impedance/inputs while waiting for buttons press/serial communication.
« Last Edit: February 17, 2019, 09:34:23 pm by Miti »
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Re: project: extending HP3478A functionality
« Reply #75 on: February 18, 2019, 09:41:44 am »
...and that kit is damn expensive.
These are pretty cheap:
https://www.aliexpress.com/item/FREE-SHIPPING-60PCS-2-54MM-6Pin-8Pin-10Pin-10MM-Long-Needle-Female-Pin-Header-Strip-Stackable/32309731519.html
However, I had to file pins a little. They are too wide for the socket used in my 3478a.

Edit: It doesn't work with external GPIB adapter in parallel with the extension for me. You may want to look at the code and see if all the lines are high impedance/inputs while waiting for buttons press/serial communication.

By design you should disable extension with serial command. But in theory it is possible to allow external GPIB master if the SRQ is not used.
Did you try the latest version (1.1)?
https://github.com/KIrill-ka/hp3478ext/releases
Ok, I need to find time to make a debugging session to see what I can do about this.
 

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Re: project: extending HP3478A functionality
« Reply #76 on: February 22, 2019, 12:04:06 pm »
Kirill,

I tried OX0 and still didn't work. It must pull some lines up or down.
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Re: project: extending HP3478A functionality
« Reply #77 on: February 22, 2019, 09:46:45 pm »
Yes, the data lines were not released after transfer. Please, try the attached version.
I tested it with HP8561E acting as GPIB master. HP8561E was able to read data from the multimeter (although, not reliably, but it works the same regardless of the hp3478ext).
Also I was able to control the HP8561E using the extension board installed  inside of HP3478A without a problem.
 

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Re: project: extending HP3478A functionality
« Reply #78 on: February 22, 2019, 11:59:06 pm »
Thanks Kirill!

It works well and I don't even have to send OX0.  :-+
I can make some suggestions, if you are open to improvements.

1. Timeout so it doesn't stay there forever waiting to select AUTOHOLD, etc.
2. Instrument GPIB address auto detection so we're not stuck with address 23 and we don't have to set it manually in the extension board. You can save it in EEPROM and validate it at power up.

I have some more but I can't remember them now.
« Last Edit: February 23, 2019, 12:00:46 am by Miti »
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Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #79 on: February 24, 2019, 10:21:24 pm »
I can make some suggestions, if you are open to improvements.
Yes, sure, any suggestions are welcome.
1. Timeout so it doesn't stay there forever waiting to select AUTOHOLD, etc.
Could you add some background, why do you think it would be useful?
If you mistakenly press the SRQ key, I think, it's faster to cycle through menu instead of waiting.

Quote
2. Instrument GPIB address auto detection so we're not stuck with address 23 and we don't have to set it manually in the extension board. You can save it in EEPROM and validate it at power up.

I guess this is meant for installations where you just don't want to use the USB interface at all.
It can be done, but it's a bit more complex than I like it...

By the way, I made it to exit the continuity tester by switching the measurement function.
 

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Re: project: extending HP3478A functionality
« Reply #80 on: February 27, 2019, 11:24:50 pm »
Could you add some background, why do you think it would be useful?
If you mistakenly press the SRQ key, I think, it's faster to cycle through menu instead of waiting.

I always find it good practice to come back to a known state if a sequence of keys was not completed. For example there is AUTOHOLD and MINMAX in all functions, V DC, V AC, 2W Ohm, 4W Ohm, mA DC, mA AC. If I press SRQ once and the phone rings, when I come back and I see AUTOHOLD on the display, I don't remember if I was in V, A, etc. If it times out, I know where I am. Nothing wrong with the way it is now, just convenience. I know,  :blah:  :-DD

I guess this is meant for installations where you just don't want to use the USB interface at all.
It can be done, but it's a bit more complex than I like it...

I should be able to use it stand alone or USB with the instrument set to any address as long as I know what address was set to. The power up sequence that I think of is:
1. Try to read something from the default address (that is stored in the EEPROM), for example send an S and see if you receive back 0<CR><LF> or 1<CR><LF>
2. If you received the expected string, do nothing, the address is correct.
3. If you don't receive the expected string, scan all the GPIB addresses  until you get the expected string and store the correct address in the EEPROM.
In general, step 3 should be executed only if the instrument GPIB has changed or it is the first install.

By the way, I made it to exit the continuity tester by switching the measurement function.

Thanks! Did you upload the hex somewhere?
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Re: project: extending HP3478A functionality
« Reply #81 on: March 04, 2019, 12:12:33 am »
Kirill,

In CONT mode, if I don't probe anything for awhile, probably about 10 minutes, the display goes blank. That's a feature the instrument if the display isn't updated for about 10 minutes. Please look at "D3text" command. Probably you don't update the display if nothing changes.
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Re: project: extending HP3478A functionality
« Reply #82 on: March 05, 2019, 04:26:01 pm »
In CONT mode, if I don't probe anything for awhile, probably about 10 minutes, the display goes blank. That's a feature the instrument if the display isn't updated for about 10 minutes. Please look at "D3text" command. Probably you don't update the display if nothing changes.

Yes, I think that's not bad. It goes back as soon as you short the leads. But I think of adding menu timeout as you suggested because of this "screensaver" thing.
The blank display while expecting menu selection doesn't seem to be good.

Did you upload the hex somewhere?
I'm in the process of adding eeprom parameters for buzzer volume and frequency (0 will disable PWM). After that I'm going to release a new version.
By the way, I've got the boards. It was a joy to solder, thanks! PC speaker sounds quite well.
Looks like it's a good idea to add a gate pull-down resistor for the buzzer driver mosfet. It gets quite warm then atmega pin is high-Z.
 

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Re: project: extending HP3478A functionality
« Reply #83 on: March 05, 2019, 11:46:36 pm »
Looks like it's a good idea to add a gate pull-down resistor for the buzzer driver mosfet. It gets quite warm then atmega pin is high-Z.

I didn't expect that output to be hi-Z but I guess that's how you turn the buzzer on and off, from DDR register. Can you add one line of code to make PB2 digital output once you turn off the buzzer and then PWM output again when you turn it on?
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Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #84 on: March 06, 2019, 11:33:04 am »
Looks like it's a good idea to add a gate pull-down resistor for the buzzer driver mosfet. It gets quite warm then atmega pin is high-Z.
I didn't expect that output to be hi-Z but I guess that's how you turn the buzzer on and off, from DDR register. Can you add one line of code to make PB2 digital output once you turn off the buzzer and then PWM output again when you turn it on?
Yes, I already did so. But it's still in hi-Z when the firmware is not running (firmware flashing, bootloader, etc.).
 

Online Miti

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Re: project: extending HP3478A functionality
« Reply #85 on: March 06, 2019, 07:25:53 pm »
Ok, I added one 100k resistor to GND and a 5 pins USB header instead of 4 pins. The majority of panel mount  USB cables to pin header have 5 pin header. Not sure when/ if I will order new Pcbs.
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Offline coromonadalix

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Re: project: extending HP3478A functionality
« Reply #86 on: March 06, 2019, 09:22:19 pm »
Should be an easy patch to do on the actual pcb's you have
 

Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #87 on: March 07, 2019, 09:44:31 am »
Should be an easy patch to do on the actual pcb's you have
There's a GND via right next to the gate. I've put a 0603 resistor and it doesn't even look like a bodge :)
One more thing. I had to trim PCB edge so it doesn't collide with mains filter capacitors.
 

Online Miti

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Re: project: extending HP3478A functionality
« Reply #88 on: March 07, 2019, 05:40:04 pm »
Can you post a picture? In my meters there's enough room to the caps but there are at least two different 3478A models.
How much did you have to trim it? My intention was to keep it all above the chassis section and don't go too close to the floating section. If it gets too close to the caps in the floating section, I don't like it.
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Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #89 on: March 07, 2019, 09:14:52 pm »
Just published a new release on the github.
The default eeprom is configured for a speaker. I added a separate eep for DC-driven buzzers.
New commands:
 Obuzz_period<p> where <p> is 0 to 65535  configures PWM period for the buzzer. 0 means DC.
 Obuzz_duty<d> where <d> is 0 to 127. 0 completely disables the buzzer. 127 is for 50% duty cycle.
 

Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #90 on: March 07, 2019, 09:39:09 pm »
The capacitor is not original, but I think it would be the same with the original caps.
 

Online Miti

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Re: project: extending HP3478A functionality
« Reply #91 on: March 08, 2019, 12:45:47 am »
I see, your pins are short. My pins are long enough to raise the board above the capacitors.
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Online Miti

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Re: project: extending HP3478A functionality
« Reply #92 on: March 08, 2019, 02:33:16 am »
Kirill,

I still see the old files on Github, the .eep and .hex are dated Aug 2018. Not that I want to update now, I'm very happy with this version. I will probably play with it once I install the USB cable that I ordered from Evilbay.
So happy that HP3478A became my go to meter for every day measurements:
- Buzzer response is very fast, at par with Fluke.
- Autohold is very fast and stable with 3 or 4 digits and reasonably fast with 5 digits.
- Min/Max works well.

I have two more suggestion for improvement:
1. Latch buzzer - minimum buzzer time. Fluke does that.
2. EEPROM autoinit - Initialize the EEPROM after a new part is programmed or after an upgrade that adds new EEPROM addresses/content. This may be harder to implement but I don't think you use many EEPROM variables.
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Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #93 on: March 08, 2019, 10:49:16 pm »
Kirill,

I still see the old files on Github, the .eep and .hex are dated Aug 2018. Not that I want to update now, I'm very happy with this version. I will probably play with it once I install the USB cable that I ordered from Evilbay.
I guess you didn't check the github project releases.
Now I've updated link in html to refer to the latest binaries (r1.2).
So happy that HP3478A became my go to meter for every day measurements:
- Buzzer response is very fast, at par with Fluke.
- Autohold is very fast and stable with 3 or 4 digits and reasonably fast with 5 digits.
- Min/Max works well.
I'm happy to hear that. I don't have another meter with an autohold function to compare.
I have two more suggestion for improvement:
1. Latch buzzer - minimum buzzer time. Fluke does that.
Ok, I'll add this. The reading rate in CONT mode is 78 rdg/sec (may be different with 60 Hz mains). So it's latched for 1/78 sec. I think of adding a parameter (N) so the buzzer will stay on for N/78 sec.
2. EEPROM autoinit - Initialize the EEPROM after a new part is programmed or after an upgrade that adds new EEPROM addresses/content. This may be harder to implement but I don't think you use many EEPROM variables.
I don't quite understand what do you want. The firmware uses the default parameter value when it sees FF's instead of something valid. This should work during upgrade as soon as parameters are not rearranged or interpreted in a different way. Recently I've added a script to configure EEPROM image files (.eep). The script may not be so user-friendly, because it requires TCL and avr toolchain installation, but it allows me to include a set of pre-configured eep's in the binary release.
 

Offline agaelema

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Re: project: extending HP3478A functionality
« Reply #94 on: March 08, 2019, 11:12:13 pm »
This upgrade of HP3478 looks awesome :o (I need to do this ). A video showing the new functions would very interesting  :-+.
 

Online Miti

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Re: project: extending HP3478A functionality
« Reply #95 on: March 09, 2019, 12:21:31 am »
The firmware uses the default parameter value when it sees FF's instead of something valid. This should work during upgrade as soon as parameters are not rearranged or interpreted in a different way.

Got it. I thought that, since you include the EEPROM image, it is mandatory to program it, otherwise it would't work properly. Since Arduino bootloader doesn't program EEPROM, that would have to be done using AVRISP.
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Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #96 on: March 09, 2019, 12:38:04 am »
Since Arduino bootloader doesn't program EEPROM...
Hmm. At least some of them do. I need to check if it works for me.
 

Online Miti

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Re: project: extending HP3478A functionality
« Reply #97 on: March 09, 2019, 02:41:29 am »
Kirill,

The buzzer doesn't work for me with Ver 1.2 and I tried both EEPROMs, I'm back to Ver 1.1. I use internal driven (DC)  buzzer. I sent Obuzz_period0 and Obuzz_duty127 even though duty shouldn't matter when period is 0... or should it?

Edit: I added a screen shot of my Fluke179 buzzer timing. The shortest buzz I could get is about 85ms.
« Last Edit: March 09, 2019, 02:58:09 am by Miti »
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Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #98 on: March 09, 2019, 11:05:26 am »
Kirill,

The buzzer doesn't work for me with Ver 1.2 and I tried both EEPROMs, I'm back to Ver 1.1. I use internal driven (DC)  buzzer.
Thank you for testing it.
I just uploaded r1.2.1, it hopefully fixes the problem.
 

Online Miti

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Re: project: extending HP3478A functionality
« Reply #99 on: March 09, 2019, 01:01:12 pm »
I just uploaded r1.2.1, it hopefully fixes the problem.

Still doesn't work for me. Beside that, it didn't even respond to SRQ key until I programmed the EEPROM. This is what I meant by "EEPROM Autoinit", after every fresh programming or upgrade, make sure it starts with a default EEPROM that works. This way, once the bootloader is programmed and the fuses configured, we don't need to use AVRISP anymore, everything is done through USB.
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Online Miti

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Re: project: extending HP3478A functionality
« Reply #100 on: March 09, 2019, 01:22:30 pm »
This upgrade of HP3478 looks awesome :o (I need to do this ). A video showing the new functions would very interesting  :-+.

https://drive.google.com/open?id=179wN6CET8ZQY1wQDYIMmN7-N4oslAw8C   :-+
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Offline agaelema

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Re: project: extending HP3478A functionality
« Reply #101 on: March 09, 2019, 02:34:06 pm »
The project is using the internal EEPROM of 328P, correct?

I searched by the main.c but I not found, just the .hex. Anyway, if the initialization of the internal EEPROM is a problem the AVR "EEMEN" allocate the variable in the EEPROM section.

Code: [Select]
"unsigned char EEMEM uc_valor = 0x33;"
http://www.nongnu.org/avr-libc/user-manual/group__avr__eeprom.html#ga79a42ec6c6c8bbbe6e34ed57a52aac59
 

Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #102 on: March 09, 2019, 06:45:23 pm »
Still doesn't work for me.
It should  :-// Maybe you didn't add W to save parameters in the EEPROM?
I tried it with DC buzzer and it works for me. The only thing, I tested it with the buzzer beeping at start (I was too much hassle to put it inside 3478A and test it there).  Anyway, I re-uploaded r1.2.1, because that debugging beep sneaked in. There were no major changes in 1.2 release so maybe you don't want to waste your time on this...
Beside that, it didn't even respond to SRQ key until I programmed the EEPROM.
Ok, I'll keep an eye on EEPROM addresses used for variables. So they don't change with the updates unless required.
This is what I meant by "EEPROM Autoinit", after every fresh programming or upgrade, make sure it starts with a default EEPROM that works. This way, once the bootloader is programmed and the fuses configured, we don't need to use AVRISP anymore, everything is done through USB.
I did program EEPROM with the bootloader.
The command is
Code: [Select]
avrdude -b 57600 -c arduino -p m328p -P /dev/ttyUSB0 -U eeprom:w:hp3478-ext-dc-buzzer.eepAs I remember, there's a fuse to erase EEPROM before programming the flash. But it shouldn't affect bootloader in any way. I can put some version code in the EEPROM to force initialization if an incompatible version is detected. But I don't think it's needed for now.
 

Online Miti

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Re: project: extending HP3478A functionality
« Reply #103 on: March 09, 2019, 10:31:32 pm »
All good now.
Thanks Kirill!  :-+
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Online Miti

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Re: project: extending HP3478A functionality
« Reply #104 on: March 21, 2019, 02:41:59 am »
Kirill,

How hard would it be to redefine the pins to your project to match the one here?

https://www.eevblog.com/forum/projects/ar488-arduino-based-gpib-adapter/

How nice would be to be able to simply program the board through USB to have functionality extension or Prologix USB-GPIB interface, as you wish?
I know that your project has some USB-GPIB functionality but it is not compatible with Prologix.
I tried the other way around, to redefine AR488 pins for my board but it doesn't work. The ports are hard coded in AR488.
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Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #105 on: March 21, 2019, 02:48:20 pm »
Miti, the buzzer pin (PB2) is a problem. There's no alternative mapping for the OC1B.
I more like the idea to implement the Prologix command set in hp3478ext. But I need a bit more motivation to do so.
Now I'm slowly advancing with multi tone continuity mode, which may be very useful for reverse engineering and fault finding.
 

Offline bitseeker

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Re: project: extending HP3478A functionality
« Reply #106 on: March 21, 2019, 05:49:41 pm »
Multi-tone continuity as in changing pitch relative to resistance? I like the sound of that (pun somewhat intended).
I TEA.
 

Online Miti

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Re: project: extending HP3478A functionality
« Reply #107 on: March 21, 2019, 07:57:53 pm »
The idea is great but the buzzer response is not linear so you'll have big variations in the intensity. But you can control the volume as well so it should be doable.
Using an internally driven buzzer woud solve the PWM output restriction.
Adding the Prologix code to your project would be nice, not sure if there's enough memory though and would take a lot of effort.
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Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #108 on: March 21, 2019, 09:08:15 pm »
Multi-tone continuity as in changing pitch relative to resistance? I like the sound of that (pun somewhat intended).
Yes. For now I have a bunch of parameters: thresholds, pwm periods and pulse lengths. After I gather some use case scenarios, I'll try to figure out a more user-friendly configuration.
 

Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #109 on: March 21, 2019, 09:18:17 pm »
The idea is great but the buzzer response is not linear so you'll have big variations in the intensity. But you can control the volume as well so it should be doable.
Yes, both pitch and volume are configurable.
Using an internally driven buzzer woud solve the PWM output restriction.
Then there would be no buzzer control  ???
I don't like the idea of supporting multiple code forks.
 

Offline coromonadalix

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Re: project: extending HP3478A functionality
« Reply #110 on: March 22, 2019, 10:28:20 am »
Dont want to be rude or start a fight 

But it seems everyone want some this or that,   and Kirill seems to be under some pressure ??

Keep this project simple,   if people are not happy    take a pause ...  take some distance ... slowly you're been pushed away from your original idea,  i consider myself lucky to have shown this project to a friend, he bought a 3478a  and he's happy with it, want to find a second one ...

The added bonus is a gift from a hard work.


The buzzer idea may have been a bad one, and having multiple code fork, will mess up everything,  unless you take no reponsability and put / add some warnings  but it will be a mess in the end

Every one can understand code constraints / code size / and hardware limits too.


Not on eevblog,  but i saw some free designs and codes dissapearing lately because of what can happen when people dont understand  ... push things to a limit.

 

Online Miti

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Re: project: extending HP3478A functionality
« Reply #111 on: March 22, 2019, 11:23:55 am »
Coromonadalix,

Thanks for policing my suggestions! Really, that's all they are, suggestions for improvement ... which Kirill asked for in the first page, if you read that page. I'm not pushing him in any direction. He, s a big boy...I guess. These are only suggestions to make an excellent project even better.

Kirill

Do you feel pushed?
« Last Edit: March 22, 2019, 11:27:35 am by Miti »
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Offline coromonadalix

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Re: project: extending HP3478A functionality
« Reply #112 on: March 22, 2019, 12:43:25 pm »
Im just saying, all initials idea are fine :)   sometimes we dont know when to stop asking for more   loll

Were using a meter who's never meant to have thoses functions added / modded etc etc ..  when it was designed

Even myself i would love to add more and more  loll 

I had two meters who had a variable buzzer tone following the read value (s),  boy it was practical,  i could hear the glitches ... 

But we may face  hardware (s) and or softwares constraints very soon ???   only Krill knows       and surely he will know when to stop ??


Okay i'll stop  loll  i'm kinda repeating myself too    loll
 

Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #113 on: March 22, 2019, 10:09:53 pm »
Do you feel pushed?
I don't  :) At my main job I don't have a direct connection to the users of our product. Even worse, there may be years until my work meets any user at all. So having some feedback is a nice experience to me.
Thank you!
... will know when to stop ??
Who knows?  ;)  Yes, the idea is to have fun of working on the project. And I agree, this is kinda fragile. Thanks for reminding, I try to keep things reasonable.
If you know VIM editor, someday it's author set a limit so all the distribution should fit one 1.44" floppy. That limit was broken, I don't think VIM project had gotten worse after that.
 

Offline bitseeker

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Re: project: extending HP3478A functionality
« Reply #114 on: March 22, 2019, 11:32:24 pm »
It's all good! :phew:
I TEA.
 

Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #115 on: April 09, 2019, 01:46:11 pm »
I've added some features & customisation parameters to the continuity mode a couple of weeks ago. It seems to work fine, but I didn't play with it a lot. So I decided to throw in a new release :)
https://github.com/KIrill-ka/hp3478ext/releases/tag/r1.3

Here's a short description of the parameters:

Code: [Select]
SETTING COMMAND            DESCRIPTION
Obeep_period<period>       beep tone used in autohold
Obeep_duty<duty>           beep volume used in autohold
Ocont_beep_ta<R-threshold> lower buzzer threshold for continuity mode
Ocont_beep_tb<R-threshold> upper buzzer threshold for continuity mode
Ocont_range<R-range>       Ohms range used in continuity mode
Ocont_thr<R-threshold>     threshold for continuity mode to start displaying the resistance value
Ocont_latch<latch-cycles>  number of measurement cycles to continue buzzing after the measured resistance gone above the cont_thr
Ocont_beep_pa<period>      beep tone for cont_beep_ta point
Ocont_beep_da<period>      beep volume for cont_beep_ta point
Ocont_beep_pb<period>      beep tone for cont_beep_tb point
Ocont_beep_db<period>      beep volume for cont_beep_tb point


VALUE          RANGE     DESCRIPTION
<period>       0-65534   frequency = 16MHz/2/<period>
                         0 means the buzzer is DC-driven
<duty>         0-127     127 means 50% duty cycle
                         0 disables the buzzer
                         for me working values are 5 to 20
<R-threshold>  0-3000    corresponds to the value displayed on the screen in 3-digit mode
<R-range>      0-6       resitance range number-1
                         refer to the HP3478A programming manual
                         the default is 1 = 300 Ohm range
<latch-cycles> 0-100     the minimal number of measurement cycles the buzzing continues
                         one cycle is ~1/75 of second
                         0 means no latch


OVER       CONT         CONT      CONT         
RANGE      THR          TB        TA           0
 |          |            |         |           |
 V          V            V         V           V
 +----------+------------+---------+-----------+
     \             \          \         \
      \             \          \         beeps using beep_da & beep_pa
       \             \          \
        \             \          beeps using values linearly interpolated from beep_pb..beep_pa & beep_db..beep_da
         \             \
          \             beeps using beep_db & beep_pb
           \
            displays "> cont_thr" (the actual effective value of cont_thr is used)
« Last Edit: April 09, 2019, 08:55:10 pm by kirill_ka »
 

Offline bitseeker

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Re: project: extending HP3478A functionality
« Reply #116 on: April 09, 2019, 04:48:25 pm »
In the last part, wouldn't the message for values over CONT THR be "> cont_thr" (greater than cont_thr) instead of "< cont_thr"?
I TEA.
 

Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #117 on: April 09, 2019, 08:56:13 pm »
Ah, yes, thanks. Corrected.
 

Offline bitseeker

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Re: project: extending HP3478A functionality
« Reply #118 on: April 09, 2019, 11:49:55 pm »
Sure thing. I haven't yet had a chance to add this to my 3478A, but still following along.
I TEA.
 

Offline yo0

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Re: project: extending HP3478A functionality
« Reply #119 on: July 21, 2019, 06:11:11 pm »
great project!, it is possible/viable  add dB measurements, frequency, and remember  the prefered digits  for example 4 1/2? thats will be great!, by the way  there is any source to buy for the project pcbs already populated like drop in solution? @Miti?

best regards.


Pio
« Last Edit: July 30, 2019, 02:52:18 am by yo0 »
 

Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #120 on: July 22, 2019, 11:13:38 am »
great project!
Thanks!
it is possible/viable  add db measurements,
It should be possible, but what do you mean by the dB?
Is it relative mode in dB? dBuV?  dBm?
frecuency
No. HP3478 can't measure frequency.
, and remember  the prefered digits  for example 4 1/2?
Yes, I was thinking of adding some kind of save state/recall state functions. That would be a lot more complex than just saving one parameter, but it would be more logical and universal solution.
 

Offline yo0

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Re: project: extending HP3478A functionality
« Reply #121 on: July 22, 2019, 12:30:58 pm »
Thanks!, i mean dBm (some fluke dmms are refereced to 600Ω) dont know if hardware is adequated  :-//


Best regards


Pio
« Last Edit: July 22, 2019, 10:56:57 pm by yo0 »
 

Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #122 on: August 12, 2019, 03:39:45 pm »
Thanks!, i mean dBm (some fluke dmms are refereced to 600Ω) dont know if hardware is adequated  :-//
Sorry for late reply, I didn't notice the post was edited. I don't know if any DMM  would provide a matching low impedance input.
My Amprobe AM-140A allows for multiple impedance references. All of them require an external termination.
I hope you understand that it would be just a mathematical function, not hardware related.
 

Offline yo0

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Re: project: extending HP3478A functionality
« Reply #123 on: August 12, 2019, 06:16:42 pm »
Thanks!, i mean dBm (some fluke dmms are refereced to 600Ω) dont know if hardware is adequated  :-//
Sorry for late reply, I didn't notice the post was edited. I don't know if any DMM  would provide a matching low impedance input.
My Amprobe AM-140A allows for multiple impedance references. All of them require an external termination.
I hope you understand that it would be just a mathematical function, not hardware related.

thank you, now i understand. i was believing was hardware related as i read in fluke 8060a manual.

just for curiosity what are/mean  the characters in diode test?  >3 Volts perhaps?

best regards.


Pio
« Last Edit: August 12, 2019, 07:01:18 pm by yo0 »
 

Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #124 on: August 12, 2019, 08:39:01 pm »
thank you, now i understand. i was believing was hardware related as i read in fluke 8060a manual.
The fluke 8060a manual says that the base specifications for dB modes are the same as DC Volts/AC Volts.
So I assume it's just a math function.
What are you going to use the dB measurements for?

just for curiosity what are/mean  the characters in diode test?  >3 Volts perhaps?
Yes. 3kOhm range used for the diode test. It gives us precise 1mA test current, ~6V open circuit, ~3V measured diode drop at max. >3V is a bit of a lie, because it will measure slightly above 3V.
 

Offline yo0

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Re: project: extending HP3478A functionality
« Reply #125 on: August 12, 2019, 10:13:38 pm »
thank you, now i understand. i was believing was hardware related as i read in fluke 8060a manual.
The fluke 8060a manual says that the base specifications for dB modes are the same as DC Volts/AC Volts.
So I assume it's just a math function.
What are you going to use the dB measurements for?

thank you! audio level adjustments in tape recorders mainly


best regards.

Pio
 

Offline coromonadalix

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Re: project: extending HP3478A functionality
« Reply #126 on: August 13, 2019, 12:22:38 am »
@yoO

You can do your math

0db is 775 mili volts  etc ... you have charts floating on the web ??
 

Offline yo0

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Re: project: extending HP3478A functionality
« Reply #127 on: August 13, 2019, 12:37:07 am »
Thank you, Yes I know, just was a suggestion of features. :)
 

Online Miti

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Re: project: extending HP3478A functionality
« Reply #128 on: August 20, 2019, 12:37:05 am »
great project!, it is possible/viable  add dB measurements, frequency, and remember  the prefered digits  for example 4 1/2? thats will be great!, by the way  there is any source to buy for the project pcbs already populated like drop in solution? @Miti?

best regards.
Pio

Sorry, I missed your question. No, I don't have fully populated boards, only bare boards.
That big spark at power up was by design!
 

Offline yo0

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Re: project: extending HP3478A functionality
« Reply #129 on: August 20, 2019, 02:49:11 am »
great project!, it is possible/viable  add dB measurements, frequency, and remember  the prefered digits  for example 4 1/2? thats will be great!, by the way  there is any source to buy for the project pcbs already populated like drop in solution? @Miti?

best regards.
Pio

Sorry, I missed your question. No, I don't have fully populated boards, only bare boards.

thank you very much, do you think can be a business oportunity for you to sell it like a finished product?  do you think there is enough demand? i think still are thousands 3478a working out there.

if not, do yo have the needed files and the bom to replicate the pcb for sale or share?, i mean for my personal use.

best regards.

Pio
« Last Edit: August 20, 2019, 03:10:06 am by yo0 »
 

Online Miti

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Re: project: extending HP3478A functionality
« Reply #130 on: August 20, 2019, 11:38:16 pm »
thank you very much, do you think can be a business oportunity for you to sell it like a finished product?  do you think there is enough demand? i think still are thousands 3478a working out there.

First of all this is Kirill's project so he should be the one to commercialise it, if he decides to. He must have put much more hours in the SW than I've put in the PCB.
Second, no, I don't see a significant commercial value in this project, designed for a dying multimeter. It is very useful, nice exercise for hobbyists though.
I'm sorry Kirill, I hope you're not offended by what I said.  ;D

Edit: I can sell you a board or two if you want. Contact me on the PM if you want.
« Last Edit: August 20, 2019, 11:39:55 pm by Miti »
That big spark at power up was by design!
 
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Offline yo0

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Re: project: extending HP3478A functionality
« Reply #131 on: August 21, 2019, 12:13:34 am »
thank you very much, do you think can be a business oportunity for you to sell it like a finished product?  do you think there is enough demand? i think still are thousands 3478a working out there.

First of all this is Kirill's project so he should be the one to commercialise it, if he decides to. He must have put much more hours in the SW than I've put in the PCB.
Second, no, I don't see a significant commercial value in this project, designed for a dying multimeter. It is very useful, nice exercise for hobbyists though.
I'm sorry Kirill, I hope you're not offended by what I said.  ;D

Edit: I can sell you a board or two if you want. Contact me on the PM if you want.

Thank for your valuable response, you're right, my apologies.

Best regards.

Pio.
 

Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #132 on: August 21, 2019, 12:25:41 pm »
Why apologise? I agree with Miti. I don't think enough items would be sold to justify the effort. Pio, just get the board and build it!
All the parts are easily available and cheap. In fact, I was able to find everything at home. By the way, I highly recommend PC-speaker style buzzer,
as I find variable tone continuity test to be very useful.
 
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Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #133 on: August 21, 2019, 12:54:27 pm »
Release 1.4 is ready.
* 5 presets can be saved and loaded. Preset 0 used after power-on (power-on SRQ should be enabled).
* Added menu timeout.
* Fixed key handling in MINMAX mode.
* Added error reporting. If something wrong happened, the error code is displayed.

There's a hidden feature. If an "ext" function used within 5 seconds before entering the menu, that function would be saved in preset.

I didn't have time to test it much as usual (this is the major advantage of non-commercial project by the way  :P).
 
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Online Miti

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Re: project: extending HP3478A functionality
« Reply #134 on: September 11, 2019, 04:02:37 pm »
Hi Kirill,

What compiler do you use?  Can it be compiled with AVR Studo? Can you post the hex and eep as you did before?

Thanks!
That big spark at power up was by design!
 

Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #135 on: September 11, 2019, 07:17:11 pm »
Hi Kirill,

What compiler do you use?  Can it be compiled with AVR Studo? Can you post the hex and eep as you did before?

Thanks!

I thought I did upload the binaries  ???
Now it's there.
https://github.com/KIrill-ka/hp3478ext/releases/download/r1.4/hp3478ext-1.4.zip

The compiler is avr-gcc. Windows package is called winavr. And yes,  it comes with AVR Studio.
 
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Online Miti

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Re: project: extending HP3478A functionality
« Reply #136 on: September 12, 2019, 05:21:39 pm »
Kirill,

Most of the externally driven buzzers are single tone, usually the sound intensity decreases significantly outside of the resonant frequency they were designed for. Did you experiment with multiple buzzers, do you have a part number to recommend?
« Last Edit: September 12, 2019, 05:37:17 pm by Miti »
That big spark at power up was by design!
 

Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #137 on: September 13, 2019, 07:36:31 pm »
Kirill,

Most of the externally driven buzzers are single tone, usually the sound intensity decreases significantly outside of the resonant frequency they were designed for. Did you experiment with multiple buzzers, do you have a part number to recommend?

I salvaged it from a PC motherboard. The part number is AC-1205G.
The datasheet shows a pronounced resonance @ 2kHz. In practice that AC-1205G sounds ok and I don't feel like it needs a freq response compensation.
https://www.eevblog.com/forum/projects/project-extending-hp3478a-functionality/msg2251509/#msg2251509
 

Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #138 on: September 13, 2019, 08:27:40 pm »
Here's the settings I use for now:
Code: [Select]
<GPIB> Ocont_ran
1    # 300 Ohm range
<GPIB> Ocont_beep_ta
5    # 0.5 Ohm resistance for beep_pa & beep_da
<GPIB> Ocont_beep_pa
2000  # 8kHz
<GPIB> Ocont_beep_pb
40000 # 400Hz
<GPIB> Ocont_beep_da
15    # 15/256*100% = ~6% duty cycle
<GPIB> Ocont_beep_db
15
<GPIB> Ocont_beep_tb
1000   # 100 Ohm resistance for beep_pb & beep_db
<GPIB> Ocont_thr
1000   # 100 Ohm threshold where it starts buzzing
<GPIB>
I just noticed a bug in handling cont_thr parameter. There's an integer overflow so it triggers at lower value than specified. I'll publish a fix for it soon.
 

Offline kirill_ka

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Re: project: extending HP3478A functionality
« Reply #139 on: September 20, 2019, 11:46:38 am »
I just noticed a bug in handling cont_thr parameter. There's an integer overflow so it triggers at lower value than specified. I'll publish a fix for it soon.
https://github.com/KIrill-ka/hp3478ext/releases/tag/r1.4.1

I spent some time trying to trace out a rare glitch where wrong data was received from GPIB.
It appeared due to the extension board had a bad contact with the socket. So I soldered contacts from 2mm pitch pin header on the top of the contacts I used previously. Note that I have an older model HP3478A which has a special socket and requires narrow contacts.
 


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