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New (to me) HP 3421A DA/C Unit, some questions
05-11-2017, 06:52 PM
Post: #1
New (to me) HP 3421A DA/C Unit, some questions
I am in the process of familiarizing myself with the 3421A Data Acquisition/Control Unit. This is the one that was in the classifieds a week or so ago. The unit arrived in great shape and with the extras as advertised. I was surprised that on AC power the DAC exhibited no calibration or other errors on power up. It would not start up from battery power, but I expected that and I installed a new battery when I opened the case to check jumper configuration and satisfy my curiosity. "No user serviceable parts inside" - Ha!

Before I opened the case, I experimented with the Control Pac ROM module with the Front Panel program with my 82162A printer in the loop. As an example, using the DVC program, it would print voltages of several batteries as I put the leads to one battery and the next. For some reason this feature stopped working before I opened the case yesterday. The printer works with the DAC in the loop as long as I am doing something initiated from the calculator, like print a program. I have tried several configurations for the loop to no avail. I even tried using a 82134A printer (with the I-L module set to Disable) and it was a no go as well.

I have been looking in the DAC manual and the ROM manual to see if there is a setting for the DAC that I inadvertently set to "no print". Since the loop is working normally otherwise, it seems to me the problem is the DAC is not sending the appropriate I-L "print this" word to the Printer. The voltages in the 41 display are changing as I move from battery to battery, but they are not printing. Anyone encounter this before?

Now that a new battery is installed on the DAC I get one error on startup under battery power: Error 7, "Failed 10 Mohm test (not within +/- 20%)". I suspect that this might be due to calibration drift. On battery power, if I run the ROM "FP" program it reports an error and halts. Interestingly, this clears the error symbol on the DAC and I can now run the "FP" program again without the error. Is this behavior caused by an old calibration, or something else?

I tested the voltage of the calibration battery when I had the case open and it is 3.1ish volts. Lithiums drop off quickly when exhausted, I suspect this one is nearly there. I am aware of the posts here about how to change the calibration battery on the HP 3468 meter without loosing calibration. Anyone care to offer advice?

Finally, I would be interested to hear what have you done with your 3421. I had a project that involved simultaneous truthing of a batch of six oxygen cells for rebreather diving that the 3421 would have been perfect for. For that application I built a test rig using an HP 3468 meter and a CMT-200 DAC running a home made six channel switch box, so that project is done. I suppose if I could find a 4465A (Option 40) board I could use the DAC to run lawn sprinkler's at my house. ;-)

For now, I am trying to decide on a general configuration of the leads from the various channels. I am thinking about how to set up utilitarian pig tails for the actuator channels 00 and 01. Channel 02 is set up with the 10:1 divider so I am planning to use it as a AC power ON/OFF sensor for program decisions so it might just get a wall plug. I will keep at least one of the 4 T type thermocouple plugs and I want to add one or two K type plugs.
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05-11-2017, 09:50 PM
Post: #2
RE: New (to me) HP 3421A DA/C Unit, some questions
(05-11-2017 06:52 PM)4ster Wrote:  Now that a new battery is installed on the DAC I get one error on startup under battery power: Error 7, "Failed 10 Mohm test (not within +/- 20%)". I suspect that this might be due to calibration drift. On battery power, if I run the ROM "FP" program it reports an error and halts. Interestingly, this clears the error symbol on the DAC and I can now run the "FP" program again without the error. Is this behavior caused by an old calibration, or something else?
Error 7 is caused by having something connected to the Mux board when the power-on self-test runs. The error symbol is cleared when the four Error Status Registers are read.

Quote:I tested the voltage of the calibration battery when I had the case open and it is 3.1ish volts. Lithiums drop off quickly when exhausted, I suspect this one is nearly there. I am aware of the posts here about how to change the calibration battery on the HP 3468 meter without loosing calibration. Anyone care to offer advice?

The 3421A uses exactly the same battery for the CAL RAM as does the 3468. There are procedures for changing the battery with external battery and AC power applied.
http://www.hpmuseum.org/cgi-sys/cgiwrap/...ead=176914
http://mrmodemhead.com/blog/hp-3468a-bat...placement/

There's an alternate procedure that saves and restores the cal constants and doesn't require powering the CAL RAM while changing the battery.
http://www.hpmuseum.org/forum/thread-8061.html

Dave
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05-12-2017, 01:42 AM
Post: #3
RE: New (to me) HP 3421A DA/C Unit, some questions
(05-11-2017 06:52 PM)4ster Wrote:  Finally, I would be interested to hear what have you done with your 3421. I had a project that involved simultaneous truthing of a batch of six oxygen cells for rebreather diving that the 3421 would have been perfect for. For that application I built a test rig using an HP 3468 meter and a CMT-200 DAC running a home made six channel switch box, so that project is done. I suppose if I could find a 4465A (Option 40) board I could use the DAC to run lawn sprinklers at my house. ;-)

My first contact with it was in 1983 when I was working in applications engineering at a company that made VHF and UHF power transistors, mostly for military communications and radars. I estimated there was about $100,000 of RF equipment per engineer in the lab, and much of it could be interfaced to, if not also controlled by, a computer, but usually wasn't. We had a lot of repetitive measurements to do on parts though. For example, Litton or other client company would be eyeing one of our parts for a particular job they had for it, and they would set up an engineering contract to evaluate the part's performance under the conditions they dictated. Part of my job was to build an amplifier that used it, and test a small lot or two or three and report the results. It got pretty repetitive and boring to do by hand, setting levels, reading meters or screens, switching things, etc..

Half the engineers had their own HP-41's. I was still using TI which was not interfaceable. I had a close friend there with a 41cv though (and lots of accessories! Smile), and the HP sales engineer came by and dropped off a 3421A for us to try. This friend took his lunch time with me and set up the 3421A at a workbench that was otherwise already set up for a job, took only 20 minutes to write a program, and had it working quickly! We put in a requisition for the 3421A and an HP-41cv with HP-IL and maybe a module or two. The company approved the 3421A, but said it was too easy for the 41cv to walk away in someone's pocket, so they ordered an IBM PC for several times the money. After three weeks of fiddling with it, the two engineers who were trying to use it were still trying to get the PC to talk to the IEEE-488 card!

A couple of years later, I was the only engineer at a tiny company that made aircraft communications equipment, and the boss decided to get into the headset market. He had the first batch of 500 coming, and I wondered how we were going to test them. Things were still unsteady enough that the testing had to be pretty thorough, not just put it on your head and talk to yourself and say, "Yeah, it works." I built a small anechoic chamber (which we called the "coffin" because that's about what it looked like) and I set up testing of the earphones and mic, partly using the 3421A, along with a few other pieces of equipment. Results were printed out, matched to the serial numbers of the headset being tested. By that time I had a 41cx (and HPIL-to-IEEE488 interface converter and plenty of other accessories), and that served as the initial controller, running a 20-page program that accessed six files. The test setup morphed over the next few years and I got my 41 back. Surprisingly, when we went to a 68000-based HP computer for the controller, the speed did not increase much, because much of the time was still spent waiting for filters to settle and readings to come back from the equipment.

I do have a pair of 3421A's here at home that I got inexpensively on eBay but have not used so far.

http://WilsonMinesCo.com (Lots of HP-41 links at the bottom of the links page, http://wilsonminesco.com/links.html )
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05-12-2017, 03:19 AM
Post: #4
RE: New (to me) HP 3421A DA/C Unit, some questions
(05-11-2017 09:50 PM)Dave Frederickson Wrote:  Error 7 is caused by having something connected to the Mux board when the power-on self-test runs. The error symbol is cleared when the four Error Status Registers are read.

Dave

What has me puzzled is that with the same initial conditions, i.e. nothing connected to the instrument, when I power up on line power there is no error 7. When I power up on battery power an error 7 occurs. That error clears by re-running the FP program.

Thanks for the links.
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05-12-2017, 03:23 AM
Post: #5
RE: New (to me) HP 3421A DA/C Unit, some questions
Thanks for the interesting examples Garth.
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05-12-2017, 03:28 PM (This post was last modified: 05-12-2017 03:30 PM by 4ster.)
Post: #6
RE: New (to me) HP 3421A DA/C Unit, some questions
Printer problem was solved: I assumed that the FP program on the module automatically set flag 21. It doesn't. I must have cleared flag 21 at some point with another program. (I thought I tested this flag setting before my initial post.)

It makes sense that the user can control the printer by not having a default SF 21 in the FP program.

Can someone familiar with the module explain the function of the CMD key on both the Front Panel and Data Logger overlays? The manual is mute about its intended use as far as I can determine. I had thought that it might be an unassigned key that could be assigned to a custom program - its not. If it is meant to run one of the sub-routines on the module, I have not been able to figure out how it works.

Steve
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05-12-2017, 03:52 PM
Post: #7
RE: New (to me) HP 3421A DA/C Unit, some questions
(05-12-2017 03:28 PM)4ster Wrote:  Can someone familiar with the module explain the function of the CMD key on both the Front Panel and Data Logger overlays? The manual is mute about its intended use as far as I can determine. I had thought that it might be an unassigned key that could be assigned to a custom program - its not. If it is meant to run one of the sub-routines on the module, I have not been able to figure out how it works.

Hi Steve,

I haven't used the 41 Control module, but I'm familiar with the 71B equivalent.

The CMD command is used to send commands to the 3421A. For example, if you wanted to set the 3421A to DC Volts and the 3V range you'd enter "F1R0" (Function 1, Range 0) in alpha and execute CMD. The equivalent for the 71B is CMD3421 and it combines the use of an OUTPUT and an ENTER statement.

Dave
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05-12-2017, 06:53 PM
Post: #8
RE: New (to me) HP 3421A DA/C Unit, some questions
(05-12-2017 03:28 PM)4ster Wrote:  Can someone familiar with the module explain the function of the CMD key on both the Front Panel and Data Logger overlays?
The manual is mute about its intended use as far as I can determine.

Hello Steve,

44468A DATA ACQUISITION/CONTROL ROM PAC Page 58
The CMD commands locate the first type 5 instrument connected to the interface, selects it and send it information of the following nature:
Code:
CMD    XROM:21,47  Contents of 41C/CV ALPHA Register.
CMDX   XROM:21,48  ALPHA Register followed by the absolute value of the integer portion of the X-Register.
CMDXY  XROM:21,49  ALPHA Register, X-Register (as with CMDX) a "comma", the absolute value of the integer portion of the Y-Register.
After the command is sent, the 41C/CV will check the instruments Status Register for a syntax error.

Sylvain
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05-13-2017, 05:58 AM
Post: #9
RE: New (to me) HP 3421A DA/C Unit, some questions
Thank you Dave and Sylvain

I missed that in the manual. It is like setting up the HP 3468 meter using the parameter codes.
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05-13-2017, 08:52 AM
Post: #10
RE: New (to me) HP 3421A DA/C Unit, some questions
I never used the accompanying module. It looks like it could make programs a little shorter. Using the Extended I/O module, I was able to easily do everything needed, and maybe with a few synthetic instructions to shorten the code. I was going through the HP82169A HPIL-to-IEEE488 interface converter though, so some of the instructions might not have worked, as IEEE-488 (HP-IB) devices did not have the autoaddressing capability. The program had this kind of look to it (I wrote up the comments for someone who's not familiar with the 41)

Code:
 90  LBL 04        \ Numeric label.  Alphanumeric labels are allowed too, but they're less efficient in this case.
 91  FC? 10        \ If it was testing the right earphone before (indicated by Flag 10 being Clear),
 92  "0046"        \ then connect the left instead.  This string of digits (as text) is a command to the Cytec relay box.
 93  "├01471145 "  \ Add to string: Disconnect +13V from DMM line, and connect microphone DC voltage line to DMM line.
 94  7
 95  SELECT        \ Now select the Cytec relay unit to talk to (whose address is #7 on the HPIB bus).  It has 128 relays.
 96  OUTA          \ OUTput the Alpha register (now containing the text string of digits formed above) to it.
 97  22
 98  SELECT        \ Now select the DMM (digital multimeter) to talk to (whose address is #22 on the bus),
 99  IND           \ and INput a Decimal number from it, which from previous set-up, makes it take a voltage reading and send it.
100  STO 17        \ STOre it in register 17.
101  FIX 02        \ Put the display mode in FIXed-point, showing two decimal places.
102  VIEW X        \ Put the resulting reading in the display.  It is also stored and will be printed later if operator chooses.
103  "01451142"    \ Disconnect the mic DCV line from the DMM and connect the mic plug tip voltage (for push-to-talk test).
104  7             \                                                  (The string of digits is a command to the relay box.)
105  SELECT        \ As above, select the Cytec relay box to talk to.
106  OUTA          \ Like line 96.  The string in line 103 gets sent to the relay box.
107  22
108  SELECT        \ Select the DMM again.
109  IND           \ Like line 99.  Get mic plug tip voltage to check for shorts to center ring or ground.
110  STO 14        \ STOre the voltage in register 14.
111  9
112  X<Y?          \ Is 9V less than the tip voltage?  (ie, is the tip voltage over 9V?)
113  GTO 05        \ If so, skip the problem message and go down to label 05.  Normally it's at the voltage of the 13V power supply.
114  SF 08         \ Set Flag 08, signaling a problem.
115  FS? 09        \ Is Flag 09 Set?  A "yes" mean it's in printout mode and should not stop with each problem but rather continue,
116  GTO 05        \ and skip the problem message in the display.  (Resume down at label 05, and print all test results at the end.)
   <snip>
137  22
138  SELECT        \ Get ready to talk to the DMM again.  (22 is the bus address of the DMM.)
139  "ACV;R,5,.02" \ Tell it to get ready to measure AC voltage with a maximum of 5V input and give .02% (1mV) precision
140  OUTA          \                                                         (This sets the range and number of digits.)
   <snip>
150  9
151  SELECT        \ Get ready to talk to the signal generator (which is at address 9 on the bus).
152  CLRDEV        \ CLeaR DEVice (like a software reset).
153  INSTAT        \ INput STATus to clear any error conditions that may exist.
154  "A.05P1I"     \ Set Amplitude of signal generator to .05V (50mV) and enable output.  The "I" makes it go ahead and execute
155  OUTA          \                                    the command string.  (Frequencies and amplitude adjustments come later.)

http://WilsonMinesCo.com (Lots of HP-41 links at the bottom of the links page, http://wilsonminesco.com/links.html )
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05-13-2017, 02:19 PM
Post: #11
RE: New (to me) HP 3421A DA/C Unit, some questions
I'll look at that carefully Garth.

As part of familiarizing myself with the new equipment I've used the DAC module's subroutines to sample my K-type thermocouples. The DAC uses T-type thermocouples in the Front Panel program. I've not tried the data logging program yet, it looks flexible.

Here is a trivial program for K-type thermocouples:

01 LBL "K-TEMP"
02 SF 21
03 "CHANNEL?"
04 PROMPT
05 ENTER^
06 LBL 00
07 FIX 0
08 ACX
09 FMT
10 FIX 1
11 XROM "TEMKX"
12 FS? 01
13 C-F
14 CLA
15 ARCL X
16 "> DEG "
17 FC? 01
18 ">C"
19 FS? 01
20 ">F"
21 ACA
22 PRBUF
23 RDN
24 FS? 00
25 GTO 00
26 END

It uses the TEMKX and C-F sub-routines from the DAC module. Set flag 0 to run an endless loop on one channel. Flag 1 converts to Fahrenheit.
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05-13-2017, 03:42 PM
Post: #12
RE: New (to me) HP 3421A DA/C Unit, some questions
(05-13-2017 08:52 AM)Garth Wilson Wrote:  139 "ACV;R,5,.02" \ Tell it to get ready to measure AC voltage with a maximum of 5V input and give .02% (1mV) precision
140 OUTA \ (This sets the range and number of digits.)

This doesn't look right as the 2431A and 3468 both have ranges of the form, 3*10^X. This makes it easy to remember the advanced range commands. Referring to the Operating and Programming Guide, p.87, if the "F1R0" command is sent as in Post #7 this will set the 3421 to DC Volts and the range to, 3*10^0 = 3V.

Referring to the manual:
ACV sets the 3421 to AC Volts, Autorange ON, Autozero ON, and 4.5 digit resolution.
R by itself does nothing and if combined with the 5, which looks like an invalid range command, is ignored.
.02 is also ignored. The ACV command will accept a channel list, but those are integers.

Garth, since you have HP-IB, are you sure this program isn't for a different instrument as the commands are very different?

Q: What HP DMM has a 5V range?

Dave
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05-13-2017, 06:54 PM
Post: #13
RE: New (to me) HP 3421A DA/C Unit, some questions
Sharp eye, Dave. The code sample above was from after some changes had been made and the 3421A was no longer part of the setup. The HP DMM was a 3457A, mounted in a rack along with other equipment. The code sample was just to show the look of the SELECTs and how the commands were formed and output without a special HP-41 module.

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