Author Topic: Some old school instruments showing how it's done (HP 3325A and Fluke 8506a)  (Read 59664 times)

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Online joeqsmith

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Re: Some old school instruments showing how it's done (HP 3325A and Fluke 8506a)
« Reply #300 on: February 17, 2021, 09:01:19 pm »
There may be software already for the Fluke meter.   I would check that first.   

If you have never used LabView,  the first thing I would suggest is you spend a day going through the getting started manual.  Work all the examples and get a basic idea how it works.  It's not magic and like any language takes time to learn.   You may also want to join their forums.   

The 5-byte data is what the LED displays.  No need to correct it like the 3-byte.  Also, no 2's comp.  So a little easier.   

I've not seen any problems using the technique I mentioned to sync up with the data.   Then again, that serial data is very slow.  But the PCs are so fast... I guess you just need to try it.

I'm sure there is software used by the military, but I haven't seen any open source software that supports the Fluke 8505/6A. I'll try looking on NI's site in case someone has uploaded something for one of the paid LabVIEW editions.

First hit on Google "labview fluke 8506a":
http://sine.ni.com/apps/utf8/niid_web_display.download_page?p_id_guid=E3B19B3E921B659CE034080020E74861


All fixed-point binary data (except the exponent byte) require two's complementing as an entire word before conversion to floating point. This is done to make the value positive before merging the fraction bits into the floating point mantissa and letting the processor figure out the bit fields for the integer portion (using FP addition). Otherwise, all single byte binary data is in signed char format (i.e., "two's complement"). So no work to do there.

That said, there are free fixed-point libraries for C++ available which would eliminate the need for conversion, but I haven't tried using them yet.


5-byte is stored in 2's comp where 3-byte requires 2's comp.   I implemented both in Labview but obviously am only using the 5-byte. 


I'm hoping to get at least 360 readings/s using the HS mode. I can do it with the external trigger input but I've yet to get it to work using bus triggering with my current setup. I plan on making an AR488 Arduino GPIB interface here soon which should solve my inability to directly control the talk/listen operation of the DMM.
..
If I can't figure out LabVIEW I may write a program in Visual Studio 2017 or Matlab to control the instrument, generate CSV files and plot the data--as I have a little more experience with them. Though, from what I can tell, LabVIEW is supposed to make doing this pretty simple. There is also a program on the forum for reading from multiple instruments but it appears to only work with SCPI instruments. I need to look through the documentation and see if I could make it work with these older meters.

I've not ran into any problems controlling various test equipment with LabView, but I've been using it for many years.   It's not something I picked up overnight.   

Offline garrettm

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Re: Some old school instruments showing how it's done (HP 3325A and Fluke 8506a)
« Reply #301 on: February 17, 2021, 09:52:30 pm »
5-byte is stored in 2's comp where 3-byte requires 2's comp.   I implemented both in Labview but obviously am only using the 5-byte.

All three binary formats use a fixed-point type where only the number of integer bits and fractional bits about the radix point is changed. Hence, the conversion is the same for each format when ignoring the error bit and implied base 10 exponent for 3-byte binary or explicit exponent byte for 5 and 6-byte binary (which is always 10^1 for voltage measurements in any binary format).

Thus, all negative valued binary data require two's complementing to convert to floating point. This is to change the signed value to unsigned, for which FP uses a sign bit rather than two's complement.

LabVIEW must have native support for fixed-point data types, otherwise negative valued readings would be incorrect. I also assume you drop the exponent byte, as it is not a part of the fixed-point word and would break the conversion if not handled separately.
« Last Edit: February 17, 2021, 09:59:36 pm by garrettm »
 

Online joeqsmith

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Re: Some old school instruments showing how it's done (HP 3325A and Fluke 8506a)
« Reply #302 on: February 17, 2021, 10:13:58 pm »
I wrote both from scratch, handling the sign, exponent and fractional parts separately.   Obviously I have not tested the 3-byte out side of the example in the manual.   For the 3-byte, I perform the 2-comp before doing anything else as the manual states.  After 2s-comp, I split it up pretty much like shown.   For the 5-byte, it is already presented as 2's comp so I just split it up.  I'm sure we are talking in circles.  Obviously I have been posting data that has been properly converted so no worries on my end.

Some conversions, like these, are not built into labview or at least not that I am aware of.  Coding them from the standard libraries has not been a problem.         

Offline garrettm

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Re: Some old school instruments showing how it's done (HP 3325A and Fluke 8506a)
« Reply #303 on: February 18, 2021, 12:07:23 am »
Here's the output of my meter on the 10V range after power up using each binary type. The decimal representation given below the hex values uses my code for the conversion.

|  Vs |  3-byte  |     5-byte     |       6-byte      |
-------------------------------------------------------
|+10V | 10 00 00 | 00 FF FF 99 01 | 00 FF FF C2 00 01 |
|-10V | F0 00 00 | FF 00 00 89 01 | FF 00 00 84 00 01 |
-------------------------------------------------------
|+10V |+10.00000 |    +9.99994    |     +9.999963      |
|-10V |-10.00000 |    -9.99992    |     -9.999921      |


I would be curious to see the output of your code with what's shown here.

The above data was collected using my 8506A and Advantest R6144 set to 10V. With average on, I saw +9.999962V and -9.999927V on the DMM’s display. With the voltage source set to +0V I got +0.00011V and for -0, -0.00009V, so it has some offset and the DMM wasn't zero corrected or warmed up. But the readings look correct to me.

All binary types returned by the DMM use two's complement format. However, only negative valued FXPs need to be two's complemented during conversion to change their bit pattern to an unsigned value of the same magnitude. Positive valued two's complement types have the same bit pattern as unsigned types and consequently can be used as is.
« Last Edit: February 18, 2021, 12:40:28 am by garrettm »
 

Offline dietert1

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Re: Some old school instruments showing how it's done (HP 3325A and Fluke 8506a)
« Reply #304 on: February 18, 2021, 10:52:35 am »
Meanwhile i performed another test on our two Fluke 8502As. I used a 650 uF film capacitor and a 100 MOhm resistor to sweep both instruments and found both of them bad.
In the "yellow" instrument the ADC is misaligned and produces steps of about 50 ppm at 10 V input and about 25 ppm every 2.5 V. The other "blue" instrument does not work with negative input voltages (random results). These instruments should really have some builtin ACAL procedure with automatic fine-tuning of the ADC ladders. Will have to setup a calibrator for them. And fix that negative voltage fault.

Appended some code i have been using to log those 3-byte messages from the instruments. Nothing nice, yet seems to work.
Meanwhile i received the Fluke Application Bulletin 25 from ArtekMedia and it includes example code showing the "!" mode and detailed timing specs (Trigger delay, ADC conversion time, data transmission time etc.). I think with a fast GPIB interface the instruments should perform up to the specs.

Regards, Dieter
 
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Offline SilverSolderTopic starter

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Re: Some old school instruments showing how it's done (HP 3325A and Fluke 8506a)
« Reply #305 on: February 18, 2021, 01:48:58 pm »

The manually tuned A/D converter is both good and bad:  good, in that it is possible to tune it...  and bad, in that it needs tuning in the first place!

 

Online joeqsmith

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Re: Some old school instruments showing how it's done (HP 3325A and Fluke 8506a)
« Reply #306 on: February 19, 2021, 01:44:26 pm »
Here's the output of my meter on the 10V range after power up using each binary type. The decimal representation given below the hex values uses my code for the conversion.

|  Vs |  3-byte  |     5-byte     |       6-byte      |
-------------------------------------------------------
|+10V | 10 00 00 | 00 FF FF 99 01 | 00 FF FF C2 00 01 |
|-10V | F0 00 00 | FF 00 00 89 01 | FF 00 00 84 00 01 |
-------------------------------------------------------
|+10V |+10.00000 |    +9.99994    |     +9.999963      |
|-10V |-10.00000 |    -9.99992    |     -9.999921      |


I would be curious to see the output of your code with what's shown here.

No problem.  For the 3-byte, do you want me to scale the data for the range?  Again, I have not tested that part.   

***
For the 5-byte,
9.9999386072  / -9.9999183416

***
Interesting about the 3-byte is that the document you link has been corrected from my manual where they had dropped the sign. 

10.0000000000 / -10.0000000000

Using the manuals example of 0xF7,0xBF, 0xFF

-5.1562595367

***
Note that I do not have support for the range scale factor.
« Last Edit: February 19, 2021, 05:01:55 pm by joeqsmith »
 

Online joeqsmith

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Re: Some old school instruments showing how it's done (HP 3325A and Fluke 8506a)
« Reply #307 on: February 20, 2021, 02:04:48 am »
With the meter now basically working, I wanted to run a longer term stability test in the lowest range (what started the whole mess).  I was looking in my stash around 1-5 ohms that was somewhat stable.  I found some old Shallcross parts marked JRBR71S.  Searching for some sort of data sheets that would show the drift, I came across this article on resistors that I found interesting.

https://www.edn.com/the-last-half-century-wirewound-resistors-part-one/
https://www.edn.com/the-last-half-century-wirewound-resistors-part-two/

I never located a data sheet or figure out what the tempco is.   



Offline SilverSolderTopic starter

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Re: Some old school instruments showing how it's done (HP 3325A and Fluke 8506a)
« Reply #308 on: February 20, 2021, 04:53:57 pm »

With the meter now basically working, I wanted to run a longer term stability test in the lowest range (what started the whole mess).  I was looking in my stash around 1-5 ohms that was somewhat stable.  I found some old Shallcross parts marked JRBR71S.  Searching for some sort of data sheets that would show the drift, I came across this article on resistors that I found interesting.

https://www.edn.com/the-last-half-century-wirewound-resistors-part-one/
https://www.edn.com/the-last-half-century-wirewound-resistors-part-two/

I never located a data sheet or figure out what the tempco is.   





Was that written by the same Mr. Pettis who is an EEVBlog member? - he seems to know his stuff!

 

Offline SilverSolderTopic starter

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Re: Some old school instruments showing how it's done (HP 3325A and Fluke 8506a)
« Reply #309 on: February 20, 2021, 05:00:52 pm »

So I got the Batronix programmer, took 4 days to ship in from Germany.




It's about the same size as the TL866.

It feels super solid, metal cabinet.  And it is able to put 21V on to the Vpp pin of the EPROM:





I tried both Intel and TI NMOS 21V chips, and both worked first time.

Bottom line, it works like a charm...   I feel it is good value at EUR 159, given the obvious care and attention that has gone into everything (hardware, software, and chip database that goes into extreme detail, even listing the EPROM variants with different timing).


 

Online joeqsmith

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Re: Some old school instruments showing how it's done (HP 3325A and Fluke 8506a)
« Reply #310 on: February 20, 2021, 05:07:43 pm »
From this datasheet, it's 232 ohm 1% 0.125W +/-30ppm.  I let it run overnight and it looks like the p-p error is 2.3mohm with a standard deviation of 0.35mohm. 

Online joeqsmith

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Re: Some old school instruments showing how it's done (HP 3325A and Fluke 8506a)
« Reply #311 on: February 20, 2021, 05:10:13 pm »

So I got the Batronix programmer, took 4 days to ship in from Germany.

....

I tried both Intel and TI NMOS 21V chips, and both worked first time.

Bottom line, it works like a charm...   I feel it is good value at EUR 159, given the obvious care and attention that has gone into everything (hardware, software, and chip database that goes into extreme detail, even listing the EPROM variants with different timing).

So you can install these parts into the meter now and they work (meter boots and everything appears normal)? 

Online joeqsmith

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Re: Some old school instruments showing how it's done (HP 3325A and Fluke 8506a)
« Reply #312 on: February 20, 2021, 06:49:37 pm »
Same ShallX part with the HP34401A, using cables shown, 100PLC.   

Offline SilverSolderTopic starter

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Re: Some old school instruments showing how it's done (HP 3325A and Fluke 8506a)
« Reply #313 on: February 20, 2021, 06:55:30 pm »

So I got the Batronix programmer, took 4 days to ship in from Germany.

....

I tried both Intel and TI NMOS 21V chips, and both worked first time.

Bottom line, it works like a charm...   I feel it is good value at EUR 159, given the obvious care and attention that has gone into everything (hardware, software, and chip database that goes into extreme detail, even listing the EPROM variants with different timing).

So you can install these parts into the meter now and they work (meter boots and everything appears normal)?

Yes, everything works perfectly so far across 4 different controllers, using Intel and TI branded 21V EPROMs, and one pair of Intel 12V EPROMs (the latter also worked fine with TL866).

The Chinese minimalist eprom eraser also works like a champ, 20 minutes to zero the chips.



 

Online joeqsmith

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Re: Some old school instruments showing how it's done (HP 3325A and Fluke 8506a)
« Reply #314 on: February 20, 2021, 08:00:02 pm »
What's the plan now?  Do you have a goal in mind for the old meter?

I checked eBay and there are a several with what I would consider some very crazy asking prices.   Maybe they are collectibles.   :-DD   

I like this one for about $900.00 with tax and shipping.  "Works",  I know what that means.  :-DD   
https://www.ebay.com/itm/Fluke-8505A-Digital-Multimeter/143819409807?epid=1400599409&hash=item217c4e098f:g:CC4AAOSwuklfoEsj

Offline dietert1

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Re: Some old school instruments showing how it's done (HP 3325A and Fluke 8506a)
« Reply #315 on: February 20, 2021, 09:32:37 pm »
They are offering two categories of equipment, one is alltest_instruments the other one alltest_surplus. If you buy from the first category, you can expect to get an instrument in perfect calibration. In the past i bought from them directly four times and was satisfied. Don't know if that 8506A is a good deal.

Regards, Dieter
 

Offline SilverSolderTopic starter

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Re: Some old school instruments showing how it's done (HP 3325A and Fluke 8506a)
« Reply #316 on: February 20, 2021, 11:40:27 pm »
What's the plan now?  Do you have a goal in mind for the old meter?

I checked eBay and there are a several with what I would consider some very crazy asking prices.   Maybe they are collectibles.   :-DD   

I like this one for about $900.00 with tax and shipping.  "Works",  I know what that means.  :-DD   
https://www.ebay.com/itm/Fluke-8505A-Digital-Multimeter/143819409807?epid=1400599409&hash=item217c4e098f:g:CC4AAOSwuklfoEsj

It certainly looks like there aren't currently as many cheap ones available on eBay as there used to be.  Covid?  Getting an instrument of this level of spec for <$100 like you did is a pretty good bargain, if you look at the alternatives...    (there is not much in that category).

I got the GPIB bus up and running again here.  I'm going to have a crack at the high speed reading mode next.  I'm thinking of using it to digitize a swept spectrum analyzer.



 

Online joeqsmith

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Re: Some old school instruments showing how it's done (HP 3325A and Fluke 8506a)
« Reply #317 on: February 20, 2021, 11:59:10 pm »
I was wondering more about trying to make sense of the firmware.   If you wanted to add a feature or fix something. 

Offline SilverSolderTopic starter

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Re: Some old school instruments showing how it's done (HP 3325A and Fluke 8506a)
« Reply #318 on: February 21, 2021, 12:10:10 am »
I was wondering more about trying to make sense of the firmware.   If you wanted to add a feature or fix something.

Getting everything on the same version is a huge win, they all behaved slightly differently before which makes it harder to automate calibration, for example.

As long as we can get the high speed reading working, it doesn't really matter what the firmware does any longer...  we will have 100% control from outside.

 

Offline m k

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Re: Some old school instruments showing how it's done (HP 3325A and Fluke 8506a)
« Reply #319 on: February 21, 2021, 11:30:33 am »
I was wondering more about trying to make sense of the firmware.   If you wanted to add a feature or fix something. 


i8080 is a notorious hardware partner.

If you check those I/O example sections of manuals of the era you'll get the idea.
Since the processor is really just that it's doings are expensive and bulky pretty fast.
Means that what ever you do is suppose to be a "custom" chip from Intel, so a rich man poor man game benefiting Intel in every corner.

This Fluke is most complicated I've tried to figure out and it has only one of those support chips, that clock maker.
That, I understand, is also a norm among these things, other hardware makers thought they really don't like that benefiting Intel part.

Outcome was what is seen here, shortage of address and data lines made people inventing all kind of custom chip alternatives.
Lack of speed wasn't a good thing eighter, though pipelining got a head start.

Few examples, 0x4000 is start of RAM and 0x8000 is start of hardware I/O where only upper half of address is inuse.

Code: [Select]
        ram:0585 21 0f 40        LXI        HL,0x400f
        ram:0588 86              ADD        (HL)
                             LAB_ram_0589                                    XREF[1]:     ram:058a(j) 
        ram:0589 be              CMP        (HL)
        ram:058a c2 89 05        JNZ        LAB_ram_0589
        ram:058d c9              RET

0x8e ohms converter
0xa2 display numbers
0xaa parallel control out
0xac parallel D7 -> ?

0xa3 display extras and 0xa2/1 enabler
0xa1 display/keyboard address

Code: [Select]
        ram:176a e5              PUSH       HL
        ram:176b 26 ae           MVI        H,0xae
                             LAB_ram_176d                                    XREF[1]:     ram:1770(j) 
        ram:176d 7e              MOV        A,(HL)
        ram:176e e6 04           ANI        0x4
        ram:1770 ca 6d 17        JZ         LAB_ram_176d
        ram:1773 26 a7           MVI        H,0xa7
        ram:1775 71              MOV        (HL),C
        ram:1776 e1              POP        HL
        ram:1777 c9              RET

I've recently wasted time with google.
Everyting seems to be plently first and then finally just junk.
I tried to find an i8080 emulator that would suite for hardware testing but found nothing.
Memory says that Altavista was better.

Obviously I had to start doing my own emulator, it's still just a shell but I'll upload it if it becomes usefull.
For a moment I thought maybe Ghidra addon can do it but then later there will be an avoidable obstacle anyway.
Advance-Aneng-Appa-AVO-Beckman-Danbridge-Data Tech-Fluke-General Radio-H. W. Sullivan-Heathkit-HP-Kaise-Kyoritsu-Leeds & Northrup-Mastech-OR-X-REO-Simpson-Sinclair-Tektronix-Tokyo Rikosha-Topward-Triplett-Tritron-YFE
(plus lesser brands from the work shop of the world)
 
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Online joeqsmith

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Re: Some old school instruments showing how it's done (HP 3325A and Fluke 8506a)
« Reply #320 on: February 21, 2021, 12:17:49 pm »
What's the plan now?  Do you have a goal in mind for the old meter?

...

I was wondering more about trying to make sense of the firmware.   If you wanted to add a feature or fix something. 

i8080 is a notorious hardware partner.

If you check those I/O example sections of manuals of the era you'll get the idea.
...
My question must not have translated very well.  I just didn't understand why anyone would invest the time.  There must be a reason, an end goal.   Maybe it's just to learn some vintage design for the fun of it.  Maybe to improve some aspect. 

Offline SilverSolderTopic starter

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Re: Some old school instruments showing how it's done (HP 3325A and Fluke 8506a)
« Reply #321 on: February 21, 2021, 04:42:11 pm »
Understanding vintage tech is always instructive.

One concrete goal might be to understand them better, so they can be kept in useful service for many years to come. There aren't many alternatives in this price range that have comparable specs, especially if you include AC in the comparison - so good examples are worth taking care of.

Another concrete goal might be finding a way to verify and perhaps even calibrate these meters (including aligning the A/D) assisted by a script running on the computer - so you could do it more often, with less calibration equipment (depending on how clever we can get), and thereby enjoy the benefits of having such a good specification meter in the first place - i.e. being able to use it for other electronics projects where measuring stuff very precisely / accurately is beneficial.

Everything depends on what we discover when we look under the hood.   If the code is a super complicated haystack, it won't be easy to do anything with it.  If there is some method to the madness in there, it may be possible to make changes - or it might be possible to leverage the fact that we know what it is doing, to "trick" it into something else.  Time will tell!  :D 

Going completely crazy, in theory, you could even make completely new modules to fit into the motherboard...    a truly crazy person could make a new controller board out of an Arduino, for example...   (I did say truly crazy!)   ;D


« Last Edit: February 21, 2021, 04:52:32 pm by SilverSolder »
 

Offline SilverSolderTopic starter

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Re: Some old school instruments showing how it's done (HP 3325A and Fluke 8506a)
« Reply #322 on: February 21, 2021, 04:51:37 pm »
I was wondering more about trying to make sense of the firmware.   If you wanted to add a feature or fix something. 


i8080 is a notorious hardware partner.

If you check those I/O example sections of manuals of the era you'll get the idea.
Since the processor is really just that it's doings are expensive and bulky pretty fast.
Means that what ever you do is suppose to be a "custom" chip from Intel, so a rich man poor man game benefiting Intel in every corner.

This Fluke is most complicated I've tried to figure out and it has only one of those support chips, that clock maker.
That, I understand, is also a norm among these things, other hardware makers thought they really don't like that benefiting Intel part.

Outcome was what is seen here, shortage of address and data lines made people inventing all kind of custom chip alternatives.
Lack of speed wasn't a good thing eighter, though pipelining got a head start.

Few examples, 0x4000 is start of RAM and 0x8000 is start of hardware I/O where only upper half of address is inuse.

Code: [Select]
        ram:0585 21 0f 40        LXI        HL,0x400f
        ram:0588 86              ADD        (HL)
                             LAB_ram_0589                                    XREF[1]:     ram:058a(j) 
        ram:0589 be              CMP        (HL)
        ram:058a c2 89 05        JNZ        LAB_ram_0589
        ram:058d c9              RET

0x8e ohms converter
0xa2 display numbers
0xaa parallel control out
0xac parallel D7 -> ?

0xa3 display extras and 0xa2/1 enabler
0xa1 display/keyboard address

Code: [Select]
        ram:176a e5              PUSH       HL
        ram:176b 26 ae           MVI        H,0xae
                             LAB_ram_176d                                    XREF[1]:     ram:1770(j) 
        ram:176d 7e              MOV        A,(HL)
        ram:176e e6 04           ANI        0x4
        ram:1770 ca 6d 17        JZ         LAB_ram_176d
        ram:1773 26 a7           MVI        H,0xa7
        ram:1775 71              MOV        (HL),C
        ram:1776 e1              POP        HL
        ram:1777 c9              RET

I've recently wasted time with google.
Everyting seems to be plently first and then finally just junk.
I tried to find an i8080 emulator that would suite for hardware testing but found nothing.
Memory says that Altavista was better.

Obviously I had to start doing my own emulator, it's still just a shell but I'll upload it if it becomes usefull.
For a moment I thought maybe Ghidra addon can do it but then later there will be an avoidable obstacle anyway.


It sounds ambitious to make an emulator!  -  but the 8080 is probably a simple enough CPU that it isn't as crazy as it sounds. 

I also noticed the lack of support chips in this design.  I guess that cost was an issue, and the designers were pretty clever.  They did manage to pack in what needed to be packed in.

Wish we could get hold of the original program listing - that would be cool! 


 

Online joeqsmith

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Re: Some old school instruments showing how it's done (HP 3325A and Fluke 8506a)
« Reply #323 on: February 21, 2021, 05:31:19 pm »
To try to make compare the two meters, I set the HP34401A to 100PLC.  I then collected data for the same length of time it took the Fluke to make the measurement.  I took the mean of that data and used that as the reading.   Basically averaging in software rather than in the meter. 

The Fluke had been running for a few days and was very stable by the time I collected the data.   In the following graph, the white is after the HP had been on for an hour.  Notice how it continued to drift for another 6 hours.     Right after setting up the measurement, it also took the Fluke another hour or so to settle out.   The Red and the Green traces are after both meters had settled.   

Online joeqsmith

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Re: Some old school instruments showing how it's done (HP 3325A and Fluke 8506a)
« Reply #324 on: February 21, 2021, 05:39:06 pm »
In this graph I have normalized both data sets to zero.  This represents roughly 15 hours of data for each meter. 


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