Agilent 34401A Hidden 10mA AC current range

[macboy]

I wonder if people know about this hidden 10 mA AC Current range. Normally, the ACI is limited to the 1 A  or the 3 A range. The following command sent over GPIB (or I assume over RS232 after sending "SYST:REMOTE") will unlock the 10 mA range. It can then be accessed from the front panel or the bus, and persists over power cycle.
To enable : "DIAG:POKE 25,0,1"
To disable : "DIAG:POKE 25,0,0"

[mikeselectricstuff]

But does it actually work, or is it relying on hardware that isn't fitted?

[sync]

I just tried it. It's working. More information from Agilent itself: http://www.home.agilent.com/agilent/editorial.jspx?ckey=1000001267:epsg:faq&id=1000001267:epsg:faq&nid=-11143.0.00&lc=fre&cc=FR

[PA0PBZ]

" and implementing the 10 mA range without the 100 mA range would require the long explanation, that you are currently reading."

That's just funny

[HighVoltage]

Very interesting,
Are there any other hidden rages or menus in the Agilent 34401A?
Thanks for this great information

[Dr. Frank]

Very interesting,
Are there any other hidden rages or menus in the Agilent 34401A?
Thanks for this great information

Nope, that's the only one, also clear fron the description, that there is no other hardware inside to add features.

That's also not that great of extension, as ACI is rarely used anyhow.
I have poked the 34401A 10 years ago already, I think, and never used that additional range, afaik.

Frank

[Psi]

it's hardly "Hidden" if Agilent themselves tell people about it

[macboy]

I'd say it is definitely "hidden" (as in not normally accessible) but not "secret".

If you think this is interesting, you may also be interested in an undocumented way to do offset-compensated 4-wire Ohms measurements...

[Dr. Frank]

I'd say it is definitely "hidden" (as in not normally accessible) but not "secret".

If you think this is interesting, you may also be interested in an undocumented way to do offset-compensated 4-wire Ohms measurements...

You mean, with the 34401A, automatically, something like OCOMP ON,  as the 3458A?

Let's hear about that, that's really interesting..

Frank

[macboy]

...
If you think this is interesting, you may also be interested in an undocumented way to do offset-compensated 4-wire Ohms measurements...

You mean, with the 34401A, automatically, something like OCOMP ON,  as the 3458A?

Let's hear about that, that's really interesting..

Frank

Automatic, sure, but not autonomous unfortunately. It requires a computer with GPIB or serial connection to the meter. The software will take a resistance measurement, then disable the current source (using more undocumented Pokes) and take another measurement, then calculate the difference. With the current source off, it is effectively measuring the thermoelectric voltage offset of the cabling since 'zero' current is flowing through the DUT, so there is 'zero' voltage to measure across it.

You can find the code (in ... Basic!) in the examples directory after installing Agilent Intuilink for the 34401A. I don't imagine many people talk to their instruments in Basic these days, but the algorithm is simple and easily implemented in your platform of choice.

[babysitter]

Call me interested in switching off the current source!

[alex.forencich]

Interesting.  I installed the IntuiLink package in a VM and found the example files.  Looks like it uses 4 different POKEs:

DIAG:POKE -2,4281,0 with no particular comment, presuming 'close front end relay'

DIAG:POKE -2,4281,4 with comment 'open front end relay'

DIAG:POKE -2,3512,0 with comment 'force front end conf to change'

DIAG:POKE 1,0,0 with comment 'force front end conf to be sent'

Basically, the code works like this:

put instrument in 2 wire ohms mode and send first poke
put instrument in 4 wire ohms mode
wait
take current source on measurement
send other 3 pokes to open relay
wait
take current source off measurement
subtract

[babysitter]

Unrelated rant: Just called Agilent Service, I sent them a workplace 34401A for calibration on Feb 9th,
ordered a calibration in their InfoLine service upfront, had a written order in the package and thought everything is well...
Wrong. They send me a email with a quote asking for confirmation, which I answered on 26th.

Still not enough, today i got:     Received 02/12/2014. Awaiting quote approval

Called, they skipped my mail but promised everything goes fine from today.

 

[coromonadalix]

Just found an vb example of this   from an intuilink installation file 

IMPORTANT NOTE:  This program describes an UNSUPPORTED CAPABILITY of the
Agilent 34401 Multimeter.  Agilent does not warrant or support the
performance or use of this feature in any manner.

Some customers want to measure lower ACI than the 1 A range allows.  The
lowest specified measurement on the 1 A range is 1% of range, or 10 mA
(see footnote 4 in data sheet).
 
The code below enables a hidden 10 mA ACI range. 
 
------------------------------------------------------------------------
 
10    !
20    !
30    ! The following program makes several ACI readings using
40    ! the undocumented 10 mA range.
50    !
60    ! The current range is enabled using the BUS and a DIAG:POKE 25,0,1
70    ! command.  Once enabled, the range can be accessed over the
80    ! BUS or from the front panel.  You can still access the range
90    ! even if power is cycled.  To disable the range you need to
100   ! to send a DIAG:POKE 25,0,0 command.
110   !
120   ! BCG 1/6/93
130   !
140   Nrdgs=10   ! NUMBER OF RDGS
150   !
160   ALLOCATE Rdgs(1:Nrdgs)
170   !
180   ASSIGN @Dvm TO 723
190   !
200   ! DIG OUT PREVIOUS ERRORS
210   !
220   CLEAR 7
230   REPEAT
240    OUTPUT @Dvm;"SYST:ERR?"
250    ENTER @Dvm;A,A$
260    PRINT A,A$
270   UNTIL A=0
280   PRINT "-----------------------------------------------------------"
290   !
300   ! SET UP 34401A
310   !
320   CLEAR @Dvm
330   OUTPUT @Dvm;"*RST"
340   WAIT .5
350   !
360   !
370   OUTPUT @Dvm;"DIAG:POKE 25,0,1"      ! Allows access to 10 mA
380   OUTPUT @Dvm;"CONF:CURR:AC .01,MIN"  ! ACI from the bus and
390   OUTPUT @Dvm;"TRIG:COUN";Nrdgs       ! front panel.
400   OUTPUT @Dvm;"READ?"
410   !
420   FOR I=1 TO Nrdgs
430    ENTER @Dvm USING "#,K";Rdgs(I)
440    PRINT I,Rdgs(I)
450    DISP I,Rdgs(I)
460   NEXT I
470 ! OUTPUT @Dvm;"DIAG:POKE 25,0,0"  ! DISABLE 10 mA RANGE
480   PRINT "-----------------------------------------------------------"
490   END

[Brandy]

What is the advantage of the vb program compared to the poke mentioned from macboy in the first post?

Btw, the "autorange" function is working upwards only. e.g. if you measure 10mA 1kHz and input a higher current value, the 34401 will change to the 1A range automatically (if you're in autorange mode). If you change from lets say 15mA/1kHz to 5mA/1kHz it will NOT switch to the 10mA range! This has to be done manually.