HP / Agilent 34401A hidden menu

[iMo]

FYI - I've spent a while messing with the new "SCALE" settings.
The GAIN and the OFFSET - the max number of digits to enter is 7 in many orders of magnitude (u,m,K,M,G), positive or negative.. Pretty handy.. 

PS:

When the SCALE is ON, the display shows 7 digits (ie 9.999,954) and it prints out 8 digits via rs232 (ie. 9.999,9543).

BUT, It seems the new STDDEV (as well as the MIN-MAX/AVRG/P-P) calculation does not work when SCALE is ON.. 

[r6502]

Hello all,

I just found this interesting thread, basically because I was searching for a possibility, to read calibration data from my 34401a.

I also had a look on the revisions of my device, and I got 03-01-01, so it must be really old firmware. Will it be possible, to update it with a newer release in general and will that be possible without loosing the calibration information? If calibration gets lost, can the calibration information be restored form the read EEPROM content? I must say, I did not read all posts in this thread.

Thanks - Guido

[rhb]

Just saw this and want a marker.  Definitely going to study the full thread.  I love the 34401A.

Reg

[Hydron]

Hello all,

I just found this interesting thread, basically because I was searching for a possibility, to read calibration data from my 34401a.

I also had a look on the revisions of my device, and I got 03-01-01, so it must be really old firmware. Will it be possible, to update it with a newer release in general and will that be possible without loosing the calibration information? If calibration gets lost, can the calibration information be restored form the read EEPROM content? I must say, I did not read all posts in this thread.

Thanks - Guido

I suspect that you are out of luck sorry - seems that later firmware will expect the updated display PCB even if you were able to put the newer FW onto the unit (see https://xdevs.com/doc/HP_Agilent_Keysight/34401A/fw/readme.txt.txt).
It may be possible to read back the cal (well, EEPROM including cal) data though if the same PEEK command works as in FW7+ (I think it was PEEK -1, but check previous posts to be sure). No guarantees though and at your own risk (I'd set cal to secure before trying).

[coromonadalix]

yes there is a FW limit for the old unobtanium display  ...   

and normally  you would need to reprogram one ic on the mainboard, and i think the display mcu too


there is tech notes about that ...

[CBrandin]

I’ve been playing around with the extended temperature settings on the 34401a. To turn on the function temperature feature you must select one of the TEMP FUNCTION options and then press ENTER. Below are all the available menu entries. Note that the entries for T/C TYPE don’t change anything, the only thermocouple type that is supported is N TYPE. Similarly, the entries for THERM TYPE also don’t change anything, the only thermistor type supported in 5 KOHM. I can’t imagine why all those options are there unless there are other memory locations that need to be entered to support them. Maybe somebody who has a version of the 34401a that supports temperature functions (that wasn’t hacked) could try out those options to see if they change anything (dimmog maybe?).

1:TEMP FUNC
   THERMISTOR
   4-WIRE RTD
   2-WIRE RTD
   T/C (Thermocouple)

2:UNITS
   DEGREES C
   DEGREES F
   KELVIN

3:RTD TYPE
   ALPHA-.00385
   ALPHA-.00391

4:RTD Ro
   Set OHMS

5:T/C Type (all types are treated as K TYPE no matter which you choose)
   K TYPE
   N TYPE
   R TYPE
   S TYPE
   T TYPE
   B TYPE
   E TYPE
   J TYPE

6:THERM TYPE (All types are treated as 5 KOHM no matter which you choose)
   2.2 KOHM
   5 KOHM
   10 KOHM

7:JUNCT TEMP (Affects T/C only, usually set to ambient temperature before T/C is mounted)
   Set DEGREES

Many thanks to all those who figured out how to unlock these features!

Chris

Update: These findings are only valid for 7-5-2 firmware.  Later versions appear to support more thermistor and T/C options.

[coromonadalix]

as we know the 34401a  has a brother 34970a ... i think there could be remnants of this in the 34401a fw

[dimmog]

as we know the 34401a  has a brother 34970a ... i think there could be remnants of this in the 34401a fw

I think the 34401A fw was released/developed before 34970A.

[iMo]

10k thermistors worked fine here:

https://www.eevblog.com/forum/testgear/hp-agilent-34401a-hidden-menu/msg4662163/#msg4662163

[CBrandin]

Strange... I tried both 10K and 5K thermistors and only the 5K ones worked. I even tested it with a 5K resistor to make sure. Maybe it depends on the firmware version you have. Mine is 7-5-2. It makes sense that later they would try out 10K thermistors as they are more common.

I wonder if later firmware versions actually support all the THERM TYPE and T/C TYPE options. My meter was likely built before the 34970a was introduced, and the later firmware versions were produced after.

Chris

[coromonadalix]

you would need to put the ic in a socket and do fw updates ??

for the front panel mcu  it's another thing ...   between the old vfd pcb and the last iteration, there is a limit on the FW versions, you can not mix them

[CBrandin]

I have no need to pursue that as the most common thermocouple type (K) is supported, 5K thermistors are commonly available and the RTD support is fine. That's already more than I need. I compared them all and they came out with pretty much matching temperature readings. I was just curious about the differences between hacked firmware versions.  I had the meter recently calibrated and I wouldn't want to have to recalibrate yet.

Chris

[thermistor-guy]

bookmarked

[thermistor-guy]

Agilent 34980A supports thermocouple, RTD, and thermistor sensors. For thermistors, manual states:

The instrument supports 2.2 kΩ (YSI Series 44004), 5 kΩ (YSI Series 44007), and 10 kΩ (YSI Series 44006) thermistors.

These are epoxy encapsulated thermistors. YSI catalog (2000) attached here for reference. The 10k device (44006) uses material H, the others use material B.

[iMo]

Strange... I tried both 10K and 5K thermistors and only the 5K ones worked. I even tested it with a 5K resistor to make sure. Maybe it depends on the firmware version you have. Mine is 7-5-2. It makes sense that later they would try out 10K thermistors as they are more common.

I wonder if later firmware versions actually support all the THERM TYPE and T/C TYPE options. My meter was likely built before the 34970a was introduced, and the later firmware versions were produced after.

Chris

Mine is 10-05-02.
On thermistor's material:
https://www.eevblog.com/forum/testgear/hp-agilent-34401a-hidden-menu/msg4659010/#msg4659010

[CBrandin]

Well, it looks like the support for temperature sensors was limited with firmware 7-5-2 and more complete with later versions.  Thanks for your feedback - i think the mystery is now resoloved 

[Dr. Frank]

Btw.: for my 3458A, 34465A, 34970A, I also have found several cheaper precision thermistors as replacements, which all fit those (identical) R(T) tables.
I think that KEYSIGHT does not offer all those thermistor types any more, one value only, maybe, and for a horrendous price.
Frank.

[CBrandin]

Keysight does sell a 5K thermistor (E2308A) which has banana plugs and a steel tube probe for measuring temperatures in fluids (although that type can be used for a number of applications). The also sell 10K thermistor kits (34308A) that have just wires and bead probe ends. I think with the meters you mention they shifted to thermistor measurements for production line applications (needing small thermistors without banana plugs).  You're right about the prices - they're very high!

[CBrandin]

iMo, Does your meter actually change anything when you switch to different THERMISTOR TYPE and TC/TYPE (assuming you have a thermocouple)? I think you can test it without needing different probes - just hook up what you have and see if readings change when you change TYPE selections. I tried that when I tested and nothing changed.

[alan.bain]

The 7-5-2 firmware in my 34401A definitely only supports 5K https://www.eevblog.com/forum/testgear/hp-agilent-34401a-hidden-menu/msg4732271/#msg4732271

Interestingly the conversion from to temp is via a rather boring bisection search of a table rather than any kind of functional law. It's one of the least interesting parts of the firmware.

The AC volts is much more interesting. Someday I should type up some of my notes on how it works and what the calibration functions do.

[iMo]

iMo, Does your meter actually change anything when you switch to different THERMISTOR TYPE and TC/TYPE (assuming you have a thermocouple)? I think you can test it without needing different probes - just hook up what you have and see if readings change when you change TYPE selections. I tried that when I tested and nothing changed.

I will try later on and will report here..

A resistor 11.95k instead of the thermistor wired 2w:
Setting 6 "thermistor type":
2k2 ...  -9.21degC
5k ...     6.25degC
10k ...   20.65degC

PS: when you go to the thermistor type try to mess with all < > up down arrows to switch around..
I somehow doubt the 5k is the only selection, as I would go with 10k if they asked me to tell a single value..

[iMo]

Are the calibration constants for the specific ranges somehow accessible?
My idea is to patch a single range (like +10V for example) with my new constant instead to go over the entire adjustment procedure..

[alan.bain]

Well this depends on what you mean. The calib constants for the DC/AC/Ohms ranges are readily accessible (see attached file cal_values which shows all the "secured" cal constants in my 34401 with some notes on what they are - base address in RAM for each constant is in the second column, but the bytes need reversing e.g. 5415 is address 1554, addresses are obviously specific to the 7-5-2 firmware).  But basically as expected for most ranges an offset and multiplier.  The AC notes are cryptic and really require some additional explanation.

But the temperature conversion is pretty unadjustable at least in rev 7-5-2. It performs a raw measurement using the meter as usual and then calls the table intepolation on the final result of the measurement.

You can see the raw measurement with DIAG:POKE 29,0,1 (don't expect much enligtenment, this is probably the same as selecting OHM or VOLT depending on sensor type and making a reading). 

For interpolation data for a 5K sensor (Ytbl-D758.txt, really a CSV, but I cannot upload csv). This is as dumped from firmware image, but as I recall first colum is resitance in ohms * 10 and second column temp deg C * 1000.  This data is hardcoded into the firmware as an interpolation table (notes suggest at 2D6F2 and 2D758 for x and y and interpolator is at 0x28A6F).

[CBrandin]

iMo, thanks for the response. This confirms my suspicion that firmware after 7-5-2  more thoroughly supported temperature functions.

I'm positive about the 5k thermistor issue (I tested thoroughly). It seems like an odd choice that they would have picked 5k instead of 10k, unless you consider the fact that HP was selling the E2308A thermistor at the time - which is a 5k thermistor.

In my testing I tried all the thermistor settings and they all resulted in the same (correct) results with a 5k thermistor and failed with 10k thermistors (I tried a few 10k thermistors). It appears that alan.bain discovered the same quirk.

I only have K thermocouples so I couldn't test other types, but I did discover that results for all the TYPE options resulted in the same (correct) readings with a K thermocouple.

It looks like they coded the menu options before they coded the firmware to support them all.

[CBrandin]

I looked up thermistor data for 2.2k, 5k, and 10k type B thermistors (which is what I think HP supported). They all have the same beta value. HP got a little lazy with the 7-5-2 firmware as all they would have had to do is scale the ohm readings for the 5k thermistor temperature table to support 2.2k and 10k thermistors.

I know this is some heavy math , but here goes:

Table lookup OHMS = measured OHMS * 5 / thermistor TYPE KOHMS - a whopping one line of code!

in fact, source code wouldn't even have to add one line of code.  Instead of table_lookup=measured_ohms, they could have changed it to table_lookup=measured_ohms*5/thermistor_type_kohms.