HP 3468A 5 multimeter - still accurate after years!

[mdanh2002]

Hi,

I haven't been to this forum in a while. Had some free time today and took out my HP3468A to test 4-wire measurement using a couple of 0.1 Ohm, 100Ohm, 1.5k and 10k precision resistors I have in my toolbox using only makeshift clips. Surprise! Multimeter reads 1.50000 and 10.0000 accurate to 3 decimal places!

The 0.1 Ohm and 100 Ohm precision resistors did not do so well - read 0.102 and 100.141 but still reasonable. considering the makeshift clips.

Attached are some photos.

 

[schmitt trigger]

Genuine Hewlett Packard stuff.......simply the best of the best instruments, before HP became a paper-and-toner company.

 

[bountyhunter]

I still remember the HP34401A was the cat's pajamas. That was always the machine I used to check others against.

 

[bountyhunter]

Genuine Hewlett Packard stuff.......simply the best of the best instruments, before HP became a paper-and-toner company.

and PC's.......

 

[mdanh2002]

I still remember the HP34401A was the cat's pajamas. That was always the machine I used to check others against.

I love my HP3468A, but unfortunately it has an internal 3V lithium battery to keep the calibration constants on SRAM. When that battery eventually dies, the multimeter will be useless unless it is recalibrated (which can't be done at home in a hobbyist lab). Hope this won't happen to me anytime soon.

I would like to own a HP34401A 6 1/2 multimeter too, but could not find a cheap one in my area.

 

[Reloadron]

The 0.1 Ohm and 100 Ohm precision resistors did not do so well - read 0.102 and 100.141 but still reasonable. considering the makeshift clips.

But do you know the actual true values of your 0.1 Ohm and 100.0 Ohm standards? Maybe the meter is lying a little and maybe the standard resistors are lying a little?

 

[spec]

I love my HP3468A, but unfortunately it has an internal 3V lithium battery to keep the calibration constants on SRAM. When that battery eventually dies, the multimeter will be useless unless it is recalibrated (which can't be done at home in a hobbyist lab). Hope this won't happen to me anytime soon.

Hy mdanh,

I lived at RAF Seletar as a kid around 1953.

As you and the other members say, the hp HP3468A is a nice instrument

Just in case you haven't got the service manual: **broken link removed**

As you say, a 3V lithium battery stores the HP3468A calibration data in SRAM, and if that calibration data is lost you have to recal, which is a pain.

But changing the 3V lithium battery is no big deal. When the mains is on the SRAM is powered by a separate mains derived supply line via a diode. When the mains is off the battery powers the SRAM via another diode.

If you are concerned about the existing battery running low, it is my understanding that all you need to do is ensure the instrument is powered by the mains and you can simply change the battery.

This is my firm understanding but, as the data in the RAM is so precious, I would double check that what is say is true.

spec

 

[bountyhunter]

I love my HP3468A, but unfortunately it has an internal 3V lithium battery to keep the calibration constants on SRAM. When that battery eventually dies, the multimeter will be useless unless it is recalibrated (which can't be done at home in a hobbyist lab). Hope this won't happen to me anytime soon.

I would like to own a HP34401A 6 1/2 multimeter too, but could not find a cheap one in my area.

I saw some on line (used/certified) for about $600 which surprised me they were that cheap. I think we used to pay a couple of grand for the new ones.

 

[MikeMl]

Genuine Hewlett Packard stuff.......simply the best of the best instruments, before HP became a paper-and-toner company.

Before that stupid *&^%# Carly Fiorina ran it into the ground. I worked for HP when it was a good company to work for, while it was still run by Bill and Dave.

 

[schmitt trigger]

MikeMi;
then you must remember the HP Journal.

A couple of months ago I read an article written in the early 70s about voltage references. It was waaaaaaaaaaaaayy ahead of its time.

 

[mdanh2002]

But do you know the actual true values of your 0.1 Ohm and 100.0 Ohm standards? Maybe the meter is lying a little and maybe the standard resistors are lying a little?

Oh, chicken and egg problem again To check the value of resistor standards, you need an accurate multimeter and to validate if the multimeter is accurate, oh well, you will need high precision resistors that have been validated elsewhere I do not have a better multimeter supporting 4-wire measurement to check. The 100 Ohm resistor reads 100.4 on my other Fluke multimeter. As for the 0.1 Ohm, it is too small to be measured without using 4-wire measurement (the resistance of the probes and cables is probably more than that).

Hy mdanh,

I lived at RAF Seletar as a kid around 1953.

As you and the other members say, the hp HP3468A is a nice instrument

Just in case you haven't got the service manual: **broken link removed**

As you say, a 3V lithium battery stores the HP3468A calibration data in SRAM, and if that calibration data is lost you have to recal, which is a pain.

But changing the 3V lithium battery is no big deal. When the mains is on the SRAM is powered by a separate mains derived supply line via a diode. When the mains is off the battery powers the SRAM via another diode.

If you are concerned about the existing battery running low, it is my understanding that all you need to do is ensure the instrument is powered by the mains and you can simply change the battery.

This is my firm understanding but, as the data in the RAM is so precious, I would double check that what is say is true.

spec

I stay quite close to Seletar in Singapore at the moment

Thanks for the link to the manual. I guess I can just try to replace the battery with the mains connected and hope that it will still work well after that.

I have a collection of vintage equipments here to play around with when I am free. See this photo for my HP 95LX, HP 200LX, HP 320LX and Psion Series 5 palmtops - all still working well decades after they were built:



The HP 320LX comes with its docking station when I got it - however after around a year the LCD has gone bad - yet the text/graphics can still be seen.