A belated thank you for this comprehensive video. I obtained the little brother to your unit - an HP 3468A - and the interface is very similar. Appreciate your effort!
Replace Elkos, they might be old. I took my 3478 to local calibration facility and they told me to replace Elkos before next calibration because that might cause noise and fluctuation. This is maybe reason for this signal twitching. When replacing Elkos be extremely careful not to short the battery.
it's funny that you say the seller isn't going to clean it up. I sell on eBay and pride myself in cleaning each and every thing I sell before it goes out and I think everyone should do the same. it only takes a few minutes
I am happy to read that, I have to say I was generalizing so sorry for that. Leave a link to your store if you like and the viewers can go over a and have a look.
I just picked one of these up for $60 on eBay. I was looking at 6.5 digit meters to get calibrated for testing and calibrating other meters but the i saw the specs on this one and realized that the accuracy is as good or better than most 6.5 ones. decided not to waste money on digits that aren't accurate. I've got a local place that will NIST cal it for $40. So for around $100 I'll have a super accurate meter. love it!
Peter Oakes so far very happy. I found an intact cal sticker on it and found out it was last calibrated november 2015 which is pretty awesome. I'm taking it to get recalibrated next week so I have a known good meter to gauge everything else from.
Peter Oakes actually maybe you can help me. I've noticed while testing that when in autorange mode in resistance the meter shows -2.something volts with the leads shorted and seems to keep that offset but when I use manual range it seems to read just fine. I'm a complete noob on this and don't even know where to begin. Any help is greatly appreciated!
I guess you're new to high precision meters. That's not a zero ohm offset in 2 wire mode. That's the resistance of the cables and banana jack/plug interfaces that you're measuring. That's the entire reason you need a 4 wire resistance mode to get a fully accurate reading: to cancel the resistance of the leads.
+solidliqs You are correct and that is what I believe I was explaining, I have been using precision equipment like this for 40 years or more, many of which was in a calibration lab. I am very aware of the effect of the cables, connectors, thermal EMF (Most felt at low voltage ranges) etc. If I did not explain in the video then I should have, either way, thanks for clarifying for the other viewers. Most DMMs etc have a null function to attempt to compensate for some of this and in the video, that's what I was looking for (Without Success) and hense switched to 4 wire mode to eliminate and prove it was the cables, connectors etc.
Be careful what you wish for -- The HP bench DMMs of this era have a hybrid IC for the input section that can fail, making repairs expensive and/or requiring the sacrifice of a parts donor DMM.
+ollopa1 very true, but from what I have seen sofar with these meters, there pretty darn reliable even considering the age, I will be doing a calibration on some of the ranges soon as I now have a 7.5 Digit Truevolt DMM from Keysight
i've found that most of those multimeters listed as broken really are broken in one way or another. usually ends up being one of the extreme measurement ranges is non functional or way out of spec like 1khz AC current. or external triggers or GPIB or RS232 are not working.
That may be true, I was expecting mine to be broken but when it arrived it was not, I think the seller did not know what was wrong, his description described it saying overload when on resistance... well that's normal and when I checked the rest of the ranges they were ok too. I have not performed a precision calibration but on comparison with other meters I have, it looks to be pretty good, certainly good enough for my purposes.
I would strongly suggest changing the lithium battery. The calibration values are held in RAM and this battery maintains the data. You need to parallel a reliable power supply, probably dry cells while removing the lithium one. See link: mrmodemhead.com/blog/hp-3468a-battery-replacement/
Wow, has that been 5 years already... I have not needed to replace the battery, it is still working and reads the right voltage, no leaks and is still accurate, not sure when I will do the follow up video at this time, I will have to re-watch my video to see where I left it.
@@TheBreadboardca if you ever replace the battery, do so while the meter is powered from mains (be careful of course) and use a gas or battery powered soldering iron to prevent short or you will lose the calibration data. I did this procedure with mine and worked like a charm.
Try not to make it too easy for the comedians. Back to the serious stuff of parting with money, retired now, and have to buy my own kit. Would the meter be still usable although out of calibration, if the battery either failed or was removed? Watching Dave Jones last night and he seemed to think it might not. Like you my own feeling is that all the basic defaults would be held in non volatile Rom. Those were the days when you needed to avoid being zapped by the HT and static problems were in the distant future.
+klystron44 Well thats an easy answer... YES The one I got stacked up as accurate as my 4.5 Digit Keysight Handhelds but of course only 1/5th the price or less and it has the HPIB interface if you want to play with remote controll and data collection. But as Jonathan Kay stated, it may be a good idea to replace the lithium cell (CAREFULLY) in order to ensure the longevitity of the settings. on my unit though the cell was still reading the full rated voltage so I was in no rush, also I now also have a 7.5 Digit Truevolt Keysight DMM so I will be doing a calibration video in the not too distant future
8 лет назад
+Peter Oakes (TheBreadboard) Hi. Be careful, as it appears that these batteries die pretty rapidly. Until then, they show full voltage. You can buy a replacement battery from Digikey, for example.
+klystron44 Thats what I thought you meant but I was going to make a funny reply :) anyway, yes, as far as I am aware the battery is used to hold the calibration data, there may be some defaults held in the main roms but any deviations would need to be in the Battery backed up RAM... Ah those where the days before flash Ram and EEPROMS
Yes, and you need to be careful when doing for instance replacement of electrolytical caps, not to short the battery with grounded soldering iron tip. I just got my calibrated in local certified calibration facility. They actually recommend to replace Elkos which I neglected to do, but before next calibration it would be done. This is one excellent instrument, battery in my 3478 is cca 30 years old and still holding.
A belated thank you for this comprehensive video. I obtained the little brother to your unit - an HP 3468A - and the interface is very similar. Appreciate your effort!
Replace Elkos, they might be old. I took my 3478 to local calibration facility and they told me to replace Elkos before next calibration because that might cause noise and fluctuation. This is maybe reason for this signal twitching. When replacing Elkos be extremely careful not to short the battery.
Nice buy :)
Anyway I'm waiting for the continuation of the power supply project sir. I hope you will make another update for that :).
Hi'gak Iya I second that!
it's funny that you say the seller isn't going to clean it up. I sell on eBay and pride myself in cleaning each and every thing I sell before it goes out and I think everyone should do the same. it only takes a few minutes
I am happy to read that, I have to say I was generalizing so sorry for that. Leave a link to your store if you like and the viewers can go over a and have a look.
I just picked one of these up for $60 on eBay. I was looking at 6.5 digit meters to get calibrated for testing and calibrating other meters but the i saw the specs on this one and realized that the accuracy is as good or better than most 6.5 ones. decided not to waste money on digits that aren't accurate. I've got a local place that will NIST cal it for $40. So for around $100 I'll have a super accurate meter. love it!
Nice buy, I hope you enjoy the meter. I have been using HP/Agilent/KeySight for over 40 years now and am still happy with the company
Peter Oakes so far very happy. I found an intact cal sticker on it and found out it was last calibrated november 2015 which is pretty awesome. I'm taking it to get recalibrated next week so I have a known good meter to gauge everything else from.
Peter Oakes actually maybe you can help me. I've noticed while testing that when in autorange mode in resistance the meter shows -2.something volts with the leads shorted and seems to keep that offset but when I use manual range it seems to read just fine. I'm a complete noob on this and don't even know where to begin. Any help is greatly appreciated!
I guess you're new to high precision meters. That's not a zero ohm offset in 2 wire mode. That's the resistance of the cables and banana jack/plug interfaces that you're measuring. That's the entire reason you need a 4 wire resistance mode to get a fully accurate reading: to cancel the resistance of the leads.
+solidliqs You are correct and that is what I believe I was explaining, I have been using precision equipment like this for 40 years or more, many of which was in a calibration lab. I am very aware of the effect of the cables, connectors, thermal EMF (Most felt at low voltage ranges) etc. If I did not explain in the video then I should have, either way, thanks for clarifying for the other viewers. Most DMMs etc have a null function to attempt to compensate for some of this and in the video, that's what I was looking for (Without Success) and hense switched to 4 wire mode to eliminate and prove it was the cables, connectors etc.
Hi, The Mostek it is not a flash Rom., she is a Rom
Be careful what you wish for -- The HP bench DMMs of this era have a hybrid IC for the input section that can fail, making repairs expensive and/or requiring the sacrifice of a parts donor DMM.
+ollopa1 very true, but from what I have seen sofar with these meters, there pretty darn reliable even considering the age, I will be doing a calibration on some of the ranges soon as I now have a 7.5 Digit Truevolt DMM from Keysight
So where is the second part with the circuit etc?
i've found that most of those multimeters listed as broken really are broken in one way or another. usually ends up being one of the extreme measurement ranges is non functional or way out of spec like 1khz AC current. or external triggers or GPIB or RS232 are not working.
That may be true, I was expecting mine to be broken but when it arrived it was not, I think the seller did not know what was wrong, his description described it saying overload when on resistance... well that's normal and when I checked the rest of the ranges they were ok too. I have not performed a precision calibration but on comparison with other meters I have, it looks to be pretty good, certainly good enough for my purposes.
I would strongly suggest changing the lithium battery. The calibration values are held in RAM and this battery maintains the data. You need to parallel a reliable power supply, probably dry cells while removing the lithium one. See link:
mrmodemhead.com/blog/hp-3468a-battery-replacement/
Did you ever replace the battery ? You also said you will have a fallow up video ?
73 N8AUM
Wow, has that been 5 years already... I have not needed to replace the battery, it is still working and reads the right voltage, no leaks and is still accurate, not sure when I will do the follow up video at this time, I will have to re-watch my video to see where I left it.
@@TheBreadboardca if you ever replace the battery, do so while the meter is powered from mains (be careful of course) and use a gas or battery powered soldering iron to prevent short or you will lose the calibration data.
I did this procedure with mine and worked like a charm.
@@ssalient thanks for the info, been good upto now, and yes, using an isolated tip iron is a good idea
Try not to make it too easy for the comedians. Back to the serious stuff of parting with money, retired now, and have to buy my own kit. Would the meter be still usable although out of calibration, if the battery either failed or was removed? Watching Dave Jones last night and he seemed to think it might not. Like you my own feeling is that all the basic defaults would be held in non volatile Rom. Those were the days when you needed to avoid being zapped by the HT and static problems were in the distant future.
+klystron44 Well thats an easy answer... YES
The one I got stacked up as accurate as my 4.5 Digit Keysight Handhelds but of course only 1/5th the price or less and it has the HPIB interface if you want to play with remote controll and data collection. But as Jonathan Kay stated, it may be a good idea to replace the lithium cell (CAREFULLY) in order to ensure the longevitity of the settings. on my unit though the cell was still reading the full rated voltage so I was in no rush, also I now also have a 7.5 Digit Truevolt Keysight DMM so I will be doing a calibration video in the not too distant future
+Peter Oakes (TheBreadboard) Hi. Be careful, as it appears that these batteries die pretty rapidly. Until then, they show full voltage. You can buy a replacement battery from Digikey, for example.
Perhaps I should rephrase that, does it need the battery to power the calibration memory?
+klystron44 Thats what I thought you meant but I was going to make a funny reply :)
anyway, yes, as far as I am aware the battery is used to hold the calibration data, there may be some defaults held in the main roms but any deviations would need to be in the Battery backed up RAM... Ah those where the days before flash Ram and EEPROMS
Yes, and you need to be careful when doing for instance replacement of electrolytical caps, not to short the battery with grounded soldering iron tip. I just got my calibrated in local certified calibration facility. They actually recommend to replace Elkos which I neglected to do, but before next calibration it would be done. This is one excellent instrument, battery in my 3478 is cca 30 years old and still holding.
Does the battery hold all the calibration data?
Should not have turned off auto zero more accurate when on
yes i discovered that soon after video was made, thanks for the input though