Lab Playground based on Agilent 34401A / RS232 / Arduino / USB / PC

[quantumvolt]

Hi.

Anyone interested in DIY accessories for their DMM? I see that most treads here are hunting for the elusive 10.000000 Volt - something that I as physicist find somewhat naive ...

No, I want to make peripherals of all kind. One example could be automated matching of resistors. The DMM can easily be externally triggered, and will promptly report the measurement in signal form. So you buy 100 pcs 1% Metal film resistors on a row or tape them on a cardboard strip or whatever and number them 01 to 99. You hook up the DMM to Arduino (or any microprocessor that you can program) and a display, and the Arduino tells you put the measurement leads on resistor 00, 01, 02 etc. The measurement values are stored in your PC. This process is done with your hands completely free. All you have to do is to shift the pair of leads from left to right when Arduino tells you to.

Then Arduino tells you to heat up the room (or a closed box with holes for your arms and a see through lid) a few degrees (we also need a temperature probe / thermometer), and you repeat the measurement process by moving the two probes from R00 to R99.

When this is over, it is easy to make a  C-program to find 1. The best pair (in the case of infinite resolution there are 100! = 9.33262154e157 possibilities ... might take some time  ), 2. The best 4 pairs (or whatever), 3. The best 3 resistors to use in a temperature compensated bridge , 4. How many pairs are available within 0.05% and so on. And the program tells you to pick R35 and R89, R19 and R07, etc. (no more resistor haystack on your desk).

This kind of kitchen science approach can involve a voltage source, current source, waveform generator, bridges, dividers, loops, probes, amplifiers, filters, sensors, capacitance / inductance module, milliOhm module (add a Arduino-controlled relay to the current leads and let Arduino double the measurements without lifting the probes by reversing the resistor current and averaging the values), and so on ...

Anyway - just wanted to say HI and ask for membership in the club. And also - since I have no access to a Calibration Lab where I live: Does anyone know a lab / person in the US that will accept a battery powered DIY 10 V Ref and a few Vishay 0.005% resistors (sent by mail) for measurement and return them by post to Thailand where I live. Thanks.

[Harvs]

Does anyone know a lab / person in the US that will accept a battery powered DIY 10 V Ref and a few Vishay 0.005% resistors (sent by mail) for measurement and return them by post to Thailand where I live. Thanks.

Would one of these suffice?  It'll be cheaper than most other options.

http://www.voltagestandard.com/DMMCheck.html

[quantumvolt]

Thanks. I'll look into it. If I buy a board from them (or GellerLab),  may be they will calibrate my other refs for a fee when I send their board in for recalib  Good idea. Thanks

[Rick Law]

Hi.

Anyone interested in DIY accessories for their DMM? I see that most treads here are hunting for the elusive 10.000000 Volt - something that I as physicist find somewhat naive ...

No, I want to make peripherals of all kind. One example could be automated matching of resistors.

...

Fellow physics guy here.  Why the trouble of using arduino?

Use a logging DMM and import the values.  A program can read the import file and filter out the resistor switching  by look for the stable values (+-1% ish) between open test lead readings as resistors change occur.

As to 8 digit DMMs, well, like car guys looking for more horse power, if it pleases them, why not.  On the other hand, if they are looking for 38 digits, now that would be kind of funny.

[quantumvolt]

Hi.

I know that all I need is a cable picking up regularly coming data. There are also tons of lab view and math software.

The Arduino is ment to be first step in USB facilitating the old 34401 (the newer 34410 has USB). Remote commanding the DMM and labeling the results also gives you the possibility to remove ALL effect of wires for lowOHM measurements. Using a 4-wire probe is not enough. Imo the current leads must also be reversed while the sense leads stays put. The two resulting measurements remove possible electric potential effects in the clip / resistor lead connection.

When this toddler's project is running I will be able to judge how much 2-way talk the DMM can do with a laptop through Arduino and added stuff. If feasible I can end up with a modern protocol remote controllable and programmable 20 years old instrument  .

And I have stopped drinking beer (too old and fat now) and my wife has left me - so I need something to do . That's why I came here, and that is where the Arduino will start help me making a kinder garden wireless online ATE 

[AlfBaz]

I'm not quite sure why you need to introduce a microcontroller between the meter and PC. Doesn't the 34401 have gpib?

Get yourself an agilent 82357B usb/gpib interface module off ebay for about $100, download their free IO library suite and write programs using one of there their interfaces.

[alm]

It does. It also has RS-232, which I guess qv is using between 34401a and Arduino. Essentially an expensive USB-RS232 converter.

[quantumvolt]

Hi and thanks. You are both right - I don't need the Arduino. But I choose to use it because imo Arduino is a fun, colorful, hobby, enthusiast open hardware platform where the net is filled with all kinds of weird ideas and users.

On the other hand - GPIB reminds me of dandruff covered, old sweat stinking, near sighted physics professors from university. I am old enough to have been using UNIVAC whole building size card reading computers when I graduated.

So I guess I am emotional. Having one leg in the grave already, I like the youthful and fun stuff. But thanks anyway - I didn't know about the converter. I guess I will buy one. Redundancy and parallel equipment are also aspects of the theory of measurement techniques.

[quantumvolt]

Thanks a for pointing me to the 82357B GPIB-USB interface. I also found E5810B LAN/GPIB/USB Gateway (more than 1000 USD) that can be connected to a Wireless Router.

This gives me a benchmark for my DIY solution. What I plan to do is to use the DMM on a 12-220 (110) V converter powered from a 12 Volt Gel MC battery / Solar Panels combined with the Arduino and XBee to make an autonomous measuring station that is wirelessly accessible for programming and data acquisition. By controlling the interfacing I can do this with any probe / sensor / instrument capable of RS232 chat.

So in a sense you are right: I am going across the river to get water (RS232 to USB). In my case it is the way to go because I will save 1000's of dollars and will have fun doing kitchen hi tech on veroboards instead of just connecting high priced ready made stuff

[alm]

If you don't care about GPIB32/VISA support (necessary for IntuiLink and Labview), you can also use the Prologix GPIB interfaces. They have a USB version ($150) and an Ethernet version ($200). They are fairly popular in hobbyist circles, and are easy to use from your own software.

A USB-RS232 converter might cost $10 or so (eg. PL2302 or FT232 based). There are also Serial-Ethernet interfaces, for example those made by Moxa. Available used for around $100. There are also WLAN versions, those are somewhat more expensive. You can also find cheap Bluetooth transceivers with serial output, these would need a level translator (eg. MAX232) to connect to the 34401a.

Nothing wrong with DIY, but you're not saving anywhere near $1000, or possibly any money at all.

[quantumvolt]

Thank you for your knowledgeable post. I have spent the day searching based on the GPIB info from this forum. It turns out there are many treads on eev about DIY GBPI USB stuff, but none seems to have turned out a finished 'open' product (except from the Canadian board - may be).

Also - I paid less than USD 200 for the DMM - and it is my first 'madness' instrument (3 1/2 digits around +-1 % is good enough for almost everything I am doing). I am retired (early) and still pay child support - so I will not pay 150-200 for a 'professional' box / converter cable (some posters claim that you could have GPIB on 8-bits home computers in the 1980's and control it in Basic). My attitude is similar to this: http://dangerousprototypes.com/forum/viewtopic.php?f=2&t=3769

I have been all over the web - it turns out you can get the PL2302 in a Nokia phone data transfer cable on eBay for a few dollars. And there is a lot of talk about FTDI USB RS232, a little Arduino stuff and even a working shield from SparkFun (Prologix clone?).

To be honest I need to digest all this. I have noticed that just the GPIB connector will set me back a small fortune (even if I just kill an old rusty cable from eBay). So I think that the first thing I will do is hook up a BNC external trig cable and half an RS232 cable to an experiment board just to get started.

It is not rocket science. I got myself a good laugh when I found this: "If you cannot find the correct cable for your configuration, you may use a wiring adapter. If you are using a DTE-to-DTE cable, make sure the adapter is a "straight-through" type. Typical adapters include gender changers, null-modem adapters, and "D" style adapters with 9 pins or 25 pins. The Agilent 34398A Cable Kit contains cables and an adapter to help you connect serial interfaces." How much do they want for this free-from-the-scrapyard hardware?

Anyway - thanks to all for their info. In less than 2 hours it is Monday here in the jungle in NE Thailand, so for me it is time to reset myself to things that concern roof, water and rice