Gossen Metrahit 28S

[Lunasix]

As another topic presents a Metrahit 25S, here is the 28S, for comparison.

[BravoV]

Wow ... quite surprise to see that hanging 2 Mhz crystal without any firm support, and just relying on it's two soldered pins.

Not a very convincing for long term reliability against mechanical vibration, isn't it ?

Is it new ?

[SeanB]

That really should have a tiny double sided tape hold down. Better than the usual hot snot or silicone, and just as reliable.

[BravoV]

That really should have a tiny double sided tape hold down. Better than the usual hot snot or silicone, and just as reliable.

Although unlikely with this battery/low power circuit, what if the big ic below it heated up ? 

Still a poor design imo, especially for this kind of pricey meter.

[Wytnucls]

The meter is discontinued. This particular one has a March 2002 calibration certificate.
They age quite well, as long as they are kept in their rubber holsters.
My 26S from 2006 looks brand new too.
Most of the crystals on these meters are free standing. Doesn't seem to affect reliability.

[robert_]

Sadly calibration requires some software that only GMC seems to have. As far as i know, there is no possibility for stand-alone calibration.
It is done over the bidirectional IR port.

Oh, i just saw it actually is availible for sale at just around 4.5k. (Gossen Metrawatt Z211F)
I really wonder why that piece of crusty old software has not yet been umm, liberated or reverse engineered in some way.
If there is a installation file floating around, patching out that licence file check probably isnt too hard...
Only other problem is it requires some pretty pricey Fluke calibrator (well, you do need some pretty pricey hardware to calibrate a 0.025% multimeter after all) to do anything productive.

[coromonadalix]

Holly !$!%$^^   that's not fun at all     unless finding a leaked iso     i'm in no luck

There a demo at Gossen but it wont simulate the 28S  ...

[robert_]

All that still wont help you unless you find a supported fluke 55xx calibrator to put that software to use.
You need some suitably accurate multifunction calibrator anyway. Manual calibration using a standard cell, KVD and loads of reference resistors and other things you also would need to have in the first place hasnt been a thing for many, many years.
Same thing with Fluke and all others. Everything a bit beyond really crappy 3 1/2 digit cheapies with a single trimpot has been software cal (using some all in one calibrator) only in the last 20 years.

So yes, you would need to have it calibrated at some cal lab, even though its expensive.

[coromonadalix]

the cpus are 

tmp87ps64f   otp cpu,  the one with the fw version, i have a 1.52 ??

gmcad30 under the crystal,  maybe a custom one ??

hd61602   lcd driver  as shown

[DrGEM]

There is a device after oxidation of batteries and broken wires. Can anyone at hand suggest the correct location of the charging wires and batteries. Thanks

[coromonadalix]

late to reply

The calibration SW can be bought for a hefty price,  but as written, you need cal equipment connected to it ...

have a new puppy
v1.52 ??

here's my wiring (attached pictures)



since mine has black  dial overlay   is it more recent or older  vs the green one    sn  is LAXXXX


no hanging crystal

and the charging port plug  has a nut ??