Author Topic: EEVblog #427 - HP 3478A Multimeter Teardown (Read 28870 times)

EEVblog · « **Reply #25 on:** February 26, 2013, 02:02:36 am »

Quote from: Smokey on February 26, 2013, 12:46:48 am

Wow. The ebay auction ended and the thing sold for AU $355.00.

Yep, more than double what I paid for it.
That's ebay Australia for you, most likely not a fan, they'd have no idea who I am.
I've seen this time and time again with stuff I've sold on ebay, people will pay silly prices to buy it from someone local in Oz instead of from overseas.
Almost every bit of test gear I've bought and sold on ebay, I've sold it higher than what I paid for it (inc postage).

Dave.

triac · « **Reply #26 on:** February 26, 2013, 01:44:03 pm »

they're not even wound in a complete single turn, looks like only half turn ?

What you see is classified as one turn.

belba · « **Reply #27 on:** March 01, 2013, 09:54:01 am »

Hello,

at http://matthieu.benoit.free.fr/cross/competitive/agilent/hp-part.htm you can find a cross-reference list of many HP marked ICs. I think it could be useful.

Guido

Buga · « **Reply #28 on:** March 02, 2013, 02:02:32 am »

Why do these high end bench meters wander around in the millivolt range where as the fluke handhelds seem to hold a zero when turned on? Is it really that sensitive to noise

c4757p · « **Reply #29 on:** March 02, 2013, 02:09:38 am »

This meter, like many other bench meters, has an input impedance specified to be "greater than 10 G" (yes, gigohms) on the low ranges. That's not enough to dissipate charge that it picks up. (If you manually switch it to a higher range, it will settle to zero.) Most of the handheld meters are 10M on all ranges.

IvoS · « **Reply #30 on:** March 04, 2013, 11:19:28 pm »

Does anyone know where I can buy a new battery for this meter? $:-\$

Dave · « **Reply #31 on:** March 07, 2013, 03:09:11 pm »

Farnell, Digikey, Mouser, anywhere really.

reagle · « **Reply #32 on:** March 12, 2013, 03:36:27 am »

Just got one for work, and did not realize that it will not take standard shrouded DMM leads. Is there a special "HP" type of leads or do I need to go down the path of chopping the shrouds off?

c4757p · « **Reply #33 on:** March 12, 2013, 03:48:14 am »

I just chop off all the shrouds. I'm not an electrician, the times when I use any voltage above 40 or 50 or so are very rare, and I would never yank an energized plug anyway. Any time I do use dangerous voltages, I prepare an entire test setup with the power completely disconnected, power it up, and all I allow myself to do without shutting down the power is push buttons. I've got too much older stuff that won't take shrouded plugs to mess around with them.

reagle · « **Reply #34 on:** March 12, 2013, 04:02:54 am »

It's just a shame to cut brand new Pomona probes, but oh well

Oddly enough, my 884x flukes of the same vintage take shrouded probes just fine. Probably due to higher voltage rating on the inputs or maybe just a bit newer

c4757p · « **Reply #35 on:** March 12, 2013, 04:06:29 am »

I think it's probably due to Fluke. They had experience making handheld stuff for use by electricians, so I imagine they'd upgrade safety sooner. HP's been mostly lab equipment with few exceptions.

SeanB · « **Reply #36 on:** March 12, 2013, 05:01:05 am »

Frankie ( Iloveelectronics) has the adaptors in his Ebay store cheap. Then you can leave the leads intact and place the adaptors in the unit permanently.

bingo600 · « **Reply #37 on:** March 21, 2013, 01:51:29 pm »

Quote from: BravoV on February 23, 2013, 12:46:23 pm

Dave mentioned the measured voltage was at 3.49 volt which is a big possibility it is a lithium thionyl chloride type (LTC) with typical at 3.6 volt instead of lithium sulfur dioxide type at typical 3 volt.

It sems to be a Panasonic 3v Lithium Cell , whatever that means. LiIon , LTC or

I just changed mine , pict here.
https://www.eevblog.com/forum/beginners/changing-battery-in-a-hp-3478a-can-i-use-a-3v-lithium/msg205742/#msg205742

/Bingo

Wim13 · « **Reply #38 on:** March 30, 2013, 08:08:10 pm »

Quote from: bingo600 on March 21, 2013, 01:51:29 pm

Quote from: BravoV on February 23, 2013, 12:46:23 pm
Dave mentioned the measured voltage was at 3.49 volt which is a big possibility it is a lithium thionyl chloride type (LTC) with typical at 3.6 volt instead of lithium sulfur dioxide type at typical 3 volt.

It sems to be a Panasonic 3v Lithium Cell , whatever that means. LiIon , LTC or
I just changed mine , pict here.
https://www.eevblog.com/forum/beginners/changing-battery-in-a-hp-3478a-can-i-use-a-3v-lithium/msg205742/#msg205742

/Bingo

No it is a: Panasonic Poly CarbonmonoFluoride Lithium batt. 3.0 Volts to the datasheet.

I replaced the batt in mine 3478, and there was also the same panasonic 3 V, see datasheet attached..

But why is the voltage 3.4 Volts.., same as above. The datasheet says 3.0 Volts..

??
does the battery charges itself with zero point energy ?

The unit i have is from 1992, so he batt is 20 years.

Just repalces it by a HQ 910a, also 1200 mAH

Rutger · « **Reply #39 on:** April 01, 2013, 02:33:56 am »

Quote from: IvoS on March 04, 2013, 11:19:28 pm

Does anyone know where I can buy a new battery for this meter? $:-\$

I got mine at Battery Plus here in the US for about $ 5.00, local pickup so no shipping cost.

madshaman · « **Reply #40 on:** April 01, 2013, 05:33:42 am »

Quote from: reagle on March 12, 2013, 04:02:54 am

It's just a shame to cut brand new Pomona probes, but oh well
Oddly enough, my 884x flukes of the same vintage take shrouded probes just fine. Probably due to higher voltage rating on the inputs or maybe just a bit newer

Pomona makes leads that have retractable shrouds for this purpose.

george graves · « **Reply #41 on:** April 13, 2013, 10:35:59 am »

Quote from: c4757p on March 02, 2013, 02:09:38 am

This meter, like many other bench meters, has an input impedance specified to be "greater than 10 G" (yes, gigohms) on the low ranges. That's not enough to dissipate charge that it picks up. (If you manually switch it to a higher range, it will settle to zero.) Most of the handheld meters are 10M on all ranges.

That's crazy. I had no idea. I too was taken back a bit when I first turned it on. "why the heck is it floating like that?!?!?" Anyways - I just picked one up on ebay for about $130 USD. Calibrated last in 2006 - tested it a bit today - calibration seems spot on. That's fine for my needs. Thanks Dave/EEVblog for turing me on to this meter. Seems like the best bang for the buck out there in the 5 1/5 digit meters.

Two things I've been thinking of...

1.) I do wish it had a back light display. I'm tempted to pull it out and see if I can't shoot some leds into the side of the glass. But at $60 for a replacement - eeek - not sure I'm brave enough to try.

2.) For 4 wire resistance measurements - I know I can use any leads I want - but why are Kelvin leads better? And is there a poor-man's alternative?

EEVblog · « **Reply #42 on:** April 13, 2013, 12:42:49 pm »

Quote from: george graves on April 13, 2013, 10:35:59 am

2.) For 4 wire resistance measurements - I know I can use any leads I want - but why are Kelvin leads better? And is there a poor-man's alternative?

Nothing special about "kelvin leads", it's the "kelvin connection" that is important. i.e. those two sense wires, they have to be connected directly to the exact point you are trying to measure. How you do that depends on what you are trying to measure.
Simply having 4 wires connected to normal crocodile clips, or say some sharp probe pins is a good enough poors mans version for general use.

alm · « **Reply #43 on:** April 13, 2013, 01:59:26 pm »

Kelvin leads are nothing special, I guess the most important reason why they're expensive is the limited market. The main thing they offer is convenience: clipping four alligator clips to each resistor gets old real fast. It's also hard to get four clips on a tiny 0805 resistor.


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Author Topic: EEVblog #427 - HP 3478A Multimeter Teardown (Read 28870 times)

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