3 ms·

I think the author's argument stands: except for novelty products, there are very few applications where the misinterpretation risk is worth less than $1. Certa

by yholio 6y ago

I think the author's argument stands: except for novelty products, there are very few applications where the misinterpretation risk is worth less than $1. Certainly nothing that has to do with safety, medical equipment, professional and industrial tooling, food processing, automotive (pressures, temperatures etc.). An one segment error leading to a 30 PSI reading when the pump is set at 90 could mean instant death when the tire blows up.

bsder 6y ago
> there are very few applications where the misinterpretation risk is worth less than $1 Any product required to run on a battery 5+ years can only be met by seven segment LCDs. That's includes safety equipment. Now what? In addition, that seven segment display has well characterized failure modes and you can make very solid statistical predictions. When was the last time you actually remember a burnt out LCD segment (I can't remember one) vs. the last time you had nasty lines running through a dot matrix LCD (happens to flat panels all the time)? On a matrix, display RAM failure is a display failure. Seven segment LCDs don't need RAM backing. Are you willing to have your medical device offline because you lost an LCD matrix row and now you are required by process to wait for a replacement? How much time and money did that cost you? These are the exceptions. LCDs are normally about cheap. And if the device isn't cheap enough, you won't have that safety/medical device at all because nobody will buy it. Engineering is tradeoffs, not absolutes.
- yholio 6y ago
  The main takeaway here is exactly this huge risk of gradual deterioration leading to invalid output that appears valid. That a thermometer fails in the hospital or runs out of battery is not a major problem - another one is close by and procedures are in place to deal with it. Meanwhile, a wrong temperature read can lead to life critical decisions by the medical staff (ex. 39 vs 33). While I agree with your engineering tradeoffs perspective, failing safe is also a major recurring theme in engineering. When errors or loss of functionality happen they should be obvious and stop the system (machine + human operators) from spiraling out of control. A compiler won't silently write integers to a byte* pointer, because that might kill your patient where the parameter goes over 255. A failed display is preferable to a working display that outputs wrong data. By the way, 14 and 16 segment displays are widely available in passive LCD formats and draw the same power, while the upgrade to dot matrix LCD is not that prohibitive, I had it on my MP3 player 15 years ago.
  - bsder 6y ago
    People make far more errors like not checking at all--and you can't even get them to use checklists which are close to free. LCD segment failure causing a misinterpretation is so far down the list of things to go wrong that it might as well be zero. 14/16 segment displays require more microcontroller pins (twice as many, in fact). That goes back to cost. Your MP3 has a very expensive, high-capacity rechargeable battery which will not hold a charge 5 years even if you connect it to nothing.

by yholio 6y ago

bsder 6y ago

> there are very few applications where the misinterpretation risk is worth less than $1 Any product required to run on a battery 5+ years can only be met by seven segment LCDs. That's includes safety equipment. Now what? In addition, that seven segment display has well characterized failure modes and you can make very solid statistical predictions. When was the last time you actually remember a burnt out LCD segment (I can't remember one) vs. the last time you had nasty lines running through a dot matrix LCD (happens to flat panels all the time)? On a matrix, display RAM failure is a display failure. Seven segment LCDs don't need RAM backing. Are you willing to have your medical device offline because you lost an LCD matrix row and now you are required by process to wait for a replacement? How much time and money did that cost you? These are the exceptions. LCDs are normally about cheap. And if the device isn't cheap enough, you won't have that safety/medical device at all because nobody will buy it. Engineering is tradeoffs, not absolutes.

yholio 6y ago
The main takeaway here is exactly this huge risk of gradual deterioration leading to invalid output that appears valid. That a thermometer fails in the hospital or runs out of battery is not a major problem - another one is close by and procedures are in place to deal with it. Meanwhile, a wrong temperature read can lead to life critical decisions by the medical staff (ex. 39 vs 33). While I agree with your engineering tradeoffs perspective, failing safe is also a major recurring theme in engineering. When errors or loss of functionality happen they should be obvious and stop the system (machine + human operators) from spiraling out of control. A compiler won't silently write integers to a byte* pointer, because that might kill your patient where the parameter goes over 255. A failed display is preferable to a working display that outputs wrong data. By the way, 14 and 16 segment displays are widely available in passive LCD formats and draw the same power, while the upgrade to dot matrix LCD is not that prohibitive, I had it on my MP3 player 15 years ago.
- bsder 6y ago
  People make far more errors like not checking at all--and you can't even get them to use checklists which are close to free. LCD segment failure causing a misinterpretation is so far down the list of things to go wrong that it might as well be zero. 14/16 segment displays require more microcontroller pins (twice as many, in fact). That goes back to cost. Your MP3 has a very expensive, high-capacity rechargeable battery which will not hold a charge 5 years even if you connect it to nothing.