TI's "fake weight"


I was at a flea market yesterday, and saw a calculator that looked interesting. It was a TI BAII Plus Professional, "advanced business analyst". I'm not a finance type, I know nothing about business, so I have no practical use for it; but it was in good condition, it felt solid and well-built, and at 5 euro it was cheap, so I bought it.

I took it home and immediately disassembled it, to see how it is built. It does seem well-built enough - and the keyboard has a decent feedback, really usable - but I was amused to see that they screwed two heavy metal plates to the back shell, just to give it a more substantial feel. I mean, the weight doesn't come from solid casing and high-quality materials: but from something added just with the purpose of making you think it's solid! :)
Personally I think it's a bit like cheating... like gold-plating a watch, or like putting a wing on a otherwise standard car, so that it just looks faster...
But I do agree that it feels good to hold it! :)



I don't think TI is the only one who does this. The pictures I have seen of the 15C LE show a black metal plate in the back housing. I can't think of any reason it would be there except to add weight. Of course for the LE the goal was to make it look, feel, and get the same results as the original, so I guess it is a special situation.


Usually thin metal is put inside for RFI protection. You don't need a thick metal plate, but a lot of HPs, including the 48, have a thin metal sheet/plate covering the board to meet FCC requirements.




The 15C LE metal has a bunch of holes and does not cover even half of the pcb.


Eric; I was once told that weight for weight or mass to mass, a mesh is better for rfi protection than a sheet. Is that true?


The point is you don't want the holes so big that the RFI can get out at the wavelengths you are trying to block. You're basically building a Faraday cage. More holes = less material = cheaper. It's reached the point where the simplest materials (like plain metal) are a big factor in the cost of electronic devices, because the electronics have gotten so cheap and commodities have gotten so expensive.

I think calculators these days probably emit so little RFI that there isn't a need for shielding anymore.



Early calculators that used inverter circuits to obtain the higher voltages needed for early MOS chips emitted a huge amount of RFI. I don't think that there were any RF emission standards for low power devices back then. For laughs take a broadcast band AM radio and put in next to an HP-35 then tune between stations. You can hear the 35 calculate!


When i was in high school i remember being able to hear my TI-30 on my am/fm cassette player.


For laughs take a broadcast band AM radio and put in next to an HP-35 then tune between stations. You can hear the 35 calculate!

At one time someone proposed that the way to tell that a lengthy TI-59 calculation had finished without watching the display was to listen to a nearby radio.

I read somewhere that TI did this with their recent calculators like the TI36X. It's not cheating, but rather paying attention to customer feedback. I doubt most people would not want to buy a calculator with a bunch of keys and light weight (just like keyboards). I just wish Casio had done it with non-HP16C alternative, the CM-100.


I didn't know this was common practice, but after all it makes sense. I can see why people like to have something that feels "heavy" in their hands. It's just that I would prefer if the weight came from a more substantial structure rather than an iron bar screwed to the shell! :)



Lightweight calculators are shirt pocket friendly. It is, after all, a *pocket* calculator, not one to fill a lead belt.


Geoffrey and Cristian are spot on. It's not just calculators. Back when Bell Telephone went to electronic sets, users felt that the phones were "cheap" feeling, so Bell added metal plates to give it the "quality" feel. We have a paradigm that associates weight with quality. Much like the humorous problem with the HP-12C revision, where accountants were uncomfortable with the increased computation speed, afraid that the calculator was rushing through the calculation. They liked to see it "doing something".


This is not unusual.

QA testing may have found that without added weight it scooted
over the desk when in use, perhaps.

Weight also sometimes gives the perception of 'substance' and

When I was at Motorola, one person told me that Moto - who for decades has made durable police radios, walkie-talkies, etc. -
in the late 80s was able to reduce the weight of their police
walkie talkies simply due to integration and materials changes.

In no way was durability or lifespan affected. But reports of 'issues' and quality drops kept coming in - after investigation, there was no substantiation but somehow "lightweight" kept coming up. Moto put some weights inside the radios without anything else
changing, and the complaints stopped.

Perception is a nasty beast.

Bill Wiese
San Jose CA


...and don't get me started on 1970's audio gear (slate end plates, pot metal ballast inside turntables, etc.) :-)



There's another more practical reason for putting weights in things. The weights make it less likely that the object will move when said movement is undesirable (for instance one would not want their calculator to go sliding around the desk when they push a button, or have a rotary dial phone spin when they try to turn the dial).

For that matter, my dishwasher has a large concrete block (I kid you not) zip-tied to the bottom part of the metal frame. The block does nothing for cleaning dishes, nothing for appearance, and I doubt anyone ever says "these darn lightweight dishwashers are junk."


There is a school of audio enthusiasts that claim that adding weight to audio components improve sound, by lowering their resonance frequency to below audio band. Hence, you see weights in turntable platters, lead shot in hollow tubes in audio racks, 150lbs loudspeakers, and so on.

There is another school that aims to low mass - and trying to have the q of that mass as low as possible (light woods, composites), trying to get a low resonance peak, but avoiding energy storage and therefore delayed release.

Another world altogether!


I suppose that's the reason I'm heavier than I used to be--- to give the impression of increased quality!


IIRC, back on the old USENET ham radio group, someone told the story of repairing an old handheld Motorola that a cop frequently used as a "billy club". It would arrive in the repair shop with bits of hair or skin stuck to knobs.

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