3458A: How do I read the Dallas non volatile SRAM date codes

[niner_007]

I'm attaching the ones on my 3458A, the firmware seems somewhat recent, and the Dallas chips were due 2017, according to an external sticker on the DMM, but unsure if they were replaced

[Kleinstein]

I read the date codes as 2007:  0717 , 0731 and 0734.  So the RAMs are some 12 years old.

[Dr. Frank]

Yes, 12 yrs. old...might work for another few years.
Save the content of the 2k nvRAM, and replace when depleted.
Version 9 is the latest firmware.
You may also add these 128k additional RAM for a few bucks
Frank

[niner_007]

thanks guys!

beside losing the calibration, what would happen if I were to replace the chips with brand new ones that had no data on them?

[martinr33]

The meter may need one power cycle to reinitialize everything.

Then you will need a full cal. That includes all of the ACV work with thermal converters.

Best approach is to dump the RAM with the utility at KE5FX http://www.ke5fx.com/gpib/readme.htm
(HP3458.exe, towards the bottom)

Once you have that in hand, you can safely remove the NVMs. Replace them with good quality sockets. Then, you can program the replacement memories with an inexpensive EPROM programmer eg TL866).

I have found that the memory can get corrupted if you just desolder it, so the backup is very handy to have.

[MiDi]

The DS1220 holds the cal-data, the two DS1230 hold the last status and recorded data.
If the unit is in cal and without cal ram errors, you want to do a backup of it.
This can be done over GPIB with special Software - see xDevs and the repair threads for this units (e.g. 3458 Worklog).
The DS1230 data is not that important unless you have special commands saved.

[aronake]

The meter may need one power cycle to reinitialize everything.

Then you will need a full cal. That includes all of the ACV work with thermal converters.

Best approach is to dump the RAM with the utility at KE5FX http://www.ke5fx.com/gpib/readme.htm
(HP3458.exe, towards the bottom)

Once you have that in hand, you can safely remove the NVMs. Replace them with good quality sockets. Then, you can program the replacement memories with an inexpensive EPROM programmer eg TL866).

I have found that the memory can get corrupted if you just desolder it, so the backup is very handy to have.

Do anybody know how to convert or load the output file of HP3458.exe into the TL866 programming software?

My HP3458.ex output file starts as below. My guess is that block 60000 should be put in block 0 of the new DS1220. But not sure if this is the case, and how to do it....

Instrument ID:HP3458A
60000 40 B9  16569
60002 E3 B9  -7239
60004 88 B9  -30535
60006 07 B9  1977
60008 4B B9  19385
6000A DC B9  -9031
6000C 96 B9  -26951
6000E E9 B9  -5703

I managed to get the caldata from the DS1220 with date code form 1996 in my 3458a. Do

[chekhov]

Best way is usually to just read them into binary file initially.

Code: [Select]

# Python 2.7 code draft ... it may even work

import os
import time
import visa

rm = visa.ResourceManager()
inst = rm.open_resource('GPIB0::22::INSTR')

def read_cal_rom(inst, cal_time):
    lo = 0x60000
    hi = 0x60000 + 2048 * 2

    try:
        inst.write("TRIG HOLD")
        inst.write("QFORMAT NUM")

        l = list()
        for i in range(lo, hi, 2):
                inst.write("MREAD {}".format(i))
                j = int(inst.read().strip())
                if j < 0:
                        j = 65536 + j
                l.append(j)

        fname = "cal-rom-{}-{}.bin".format(cal_time, time.strftime("%d.%m.%Y-%H:%M:%S", time.localtime(cal_time)))
        with open(os.path.join("/home/pi/3458a-meas/calram-dumps", fname), "w") as f:
            for i in l:
                f.write("%c" % (i >> 8))
            f.flush()
        print "CAL ROM read ok"
    except:
        print "CAL ROM reading failed: {}".format(e)
        pass

    inst.write("QFORMAT NORM")
    inst.write("TRIG AUTO")

read_cal_rom(inst, time.time())


[IanJ]

If you are on Windows then WinGPIB has a utility built in to save out via GPIB the cal ram and settings ram contents. 3458A and 3457A actually.
I tested this against the DOS app that is out there for the 3458A that does the same thing (cal ram) and it presented the same file.

Before desoldering very much advised to get the data out.

Ian.

[aronake]

If you are on Windows then WinGPIB has a utility built in to save out via GPIB the cal ram and settings ram contents. 3458A and 3457A actually.
I tested this against the DOS app that is out there for the 3458A that does the same thing (cal ram) and it presented the same file.

Before desoldering very much advised to get the data out.

Ian.

Thanks! Great suggestion! Awesome software! I have seen this software in your videos calibrating PDVS2minis, but didn't know you had made it available.