LOW TEMP LCD

[deCompression]

Hey guys,

what's the difference between a LOW TEMP LCD and a normal LCD?


For example the GLS-6900 is equipped with an LOW TEMP LCD.




What other technology would be installed here?

[d2mac]

The idea is, that some special liquid crystals are more fluid in the cold then other.

So under an specific tempertature every liquid will get lazy.
The LCD will then not show anything.

You can try that in a freezer (-20°C or below) with a low temp G and a generic G.

Post pics here if you do!

[Seriously]

That ^^

LCD displays on any products start to get sluggish in colder temps , so they've made one that goes down to colder temps.......... do they specify any particular temp?

[d2mac]

That ^^

LCD displays on any products start to get sluggish in colder temps , so they've made one that goes down to colder temps.......... do they specify any particular temp?

Yes, they do (from G-9000):
Specifications

• 
  
  • Case / bezel material: Resin / Stainless steel
  • Resin Band
  • Shock Resistant
  • Mineral Glass
  • Mud Resistant
  • 200-meter water resistance
  
  
  
  • Electro-luminescent backlight
    Auto light switch, dual illuminator, selectable illumination duration, afterglow
  • Flash alert
    Flashes with buzzer that sounds for alarms, hourly time signal, countdown timer time up alarm, countdown timer progress beeper, and stopwatch auto start
  • Low temperature resistant (-20°C)
  • World time
    29 time zones (48 cities), city code display, daylight saving on/off
  • 1/100-second stopwatch (ST1)
    Measuring capacity: 999:59'59.99''
    Measuring modes: Elapsed time, split time, 1st-2nd place times
    Other: Auto start
  • 1/100-second stopwatch (ST2)
    Measuring capacity: 999:59'59.99''
    Measuring modes: Elapsed time, split time, 1st-2nd place times
  • Countdown timer
    Measuring unit: 1 second
    Countdown range: 24 hours
    Countdown start time setting range: 1 minute to 24 hours (1-minute increments and 1-hour increments)
    Others: Auto-repeat, progress beeper
  • Multi-function alarms
    5 independent multi-function alarms (4 one-time alarms and 1 snooze alarm)
  • Hourly time signal
  • Full auto-calendar (to year 2099)
  • 12/24-hour format
  • Button operation tone on/off
  • Regular timekeeping: Hour, minute, second, pm, month, date, day
  • Accuracy: ±15 seconds per month
  • Approx. battery life: 3 years on CR2025
  
  
  

[deCompression]

The idea is, that some special liquid crystals are more fluid in the cold then other.

So under an specific tempertature every liquid will get lazy.
The LCD will then not show anything.

You can try that in a freezer (-20°C or below) with a low temp G and a generic G.

Post pics here if you do!

That means that in various G's the LCD liquid is more fluid than in other G's ?

[d2mac]

Yes, different types of liquid crystal!

That means that in various G's the LCD liquid is more fluid than in other G's ?

[Seriously]

Found this informative page on the problem.

Liquid Crystal Display Temperature Range

There are two main design considerations that determine the operating temperature range of a given liquid crystal display. They are: The liquid crystal fluid used in the display, and The mux rate of the display. Luckily, both of these things are well within our control, and an understanding of these two characteristics should guarantee an acceptable design. We will make a leap of faith here and assume that there is enough voltage available to properly drive the display, so it should not be an issue. If you need a refresher on driving voltage, go to our Optimum Drive Voltage page for a quick recap. How Mux Rate Effects the Operating Temperature Range When considering the multiplex rate of a liquid crystal display, the best advice I can give can be summed up in a single word, don't. Nothing good happens when a display is multiplexed, and it should be avoided at all costs. The display contrast, viewing angle, and temperature range all suffer, and knowing this, the design goal is to minimize the damage by keeping the mux rate as low as possible. The reason for this degradation is simple. When a display is multiplexed, it is essentially driven a time-division manner. That is, a segment, or a set of segments, are activated for a short time slice. These segments are then allowed to turn themselves off while a second set of segments is turned on. This back and forth time slicing means that each segment set is not really turned on all the way, and they never really turn off all the way. They operate in a region that is a compromise of drive on and off voltages. The higher the mux rate, the less time a given group of segments is being addressed , and the worse the display will look. If you refer to our "Basic Operation of an LCD " page, it is easy to see that this is not a good situation. As a practical matter, a mux rate of 2:1, 3:1 or maybe even 4:1(?) for a normal TN display will not really damage the contrast and viewing angle very much. For mux rates above 4:1, serious degradation sets in. At that point, a switch of drivers or a move to STN technology are the options. How the Liquid Crystal Fluid affects the Operating Temperature Range The liquid crystal fluid in the display is of prime importance. Different fluids have much different temperature characteristics, and it is up to the designer to select a fluid that fulfills the necessary requirement. Below is a graph of the response of a hypothetical LCD fluid in a direct drive circuit over temperature range, and is typical of an average TN fluid: As can be seen, the voltage threshold of this fluid is not linear across its entire temperature range, however, it is relatively constant for a range of "about" -20oC to 85oC. The threshold graph does however go up rather steeply when the temperature range gets down to about -25oC. The "about" point on the graph is in the eye of the designer, and it must be understood that this is not a number that is cast in stone, but rather an interpretation of the data. It may be stated that a display built using the above hypothetical fluid, will have an operating temperature range of -40oc to +105oc when used in a direct drive mode. However, it can be seen that at -40oc the drive voltage goes to an impractical level. The result of this non-linearity is that you need to increase the drive voltage at low temperatures for an acceptable looking display, and lower the drive voltage at higher temperatures to prevent "ghosting". In most applications, a temperature range of -40oc to +85oc is sufficient, however for unusual applications, fluids are available with operational temperature ranges as low as -55oC and as high as +125oC. Fluids that have relatively flat response curves from -40oC to +85oC are readily available. The temperature specifications for all LCD fluids are shown in the manufacturers data sheet. If these parameters are important, please request this data from your supplier,(hopefully Liquid Crystal Technologies.)

For a couple more informative pages see: http://www.liquidcrystaltechnologies...port/basop.htm

and the chemistry involved…...

Several different families of liquid crystals are used in liquid crystals. The molecules used have to be anisotropic, and to exhibit mutual attraction. Polarizable rod-shaped molecules (biphenyls, terphenyls, etc.) are common.
A common form is a pair of aromatic benzene rings, with a nonpolar moiety (pentyl, heptyl, octyl, or alkyl oxy group) on one end and polar (nitrile, halogen) on the other. Sometimes the benzene rings are separated with an acetylene group, ethylene, CH=N, CH=NO, N=N, N=NO, or ester group. In practice, eutectic mixtures of several chemicals are used, to achieve wider temperature operating range (-10..+60 °C for low-end and -20..+100 °C for high-performance displays).
For example, the E7 mixture is composed of three biphenyls and one terphenyl: 39 wt.% of 4'-pentyl[1,1'-biphenyl]-4-carbonitrile (nematic range 24..35 °C), 36 wt.% of 4'-heptyl[1,1'-biphenyl]-4-carbonitrile (nematic range 30..43 °C), 16 wt.% of 4'-octoxy[1,1'-biphenyl]-4-carbonitrile (nematic range 54..80 °C), and 9 wt.% of 4-pentyl[1,1':4',1-terphenyl]-4-carbonitrile (nematic range 131..240 °C).

[deCompression]

Which G's are equipped with an LOW TEMP LCD ?

The GLS-6900 also -20°C

[is that my watch]

think the GLS100-3 does minus 20 if I remember right



think there was a thread on wus about this way back when think there was all most a complete list of models at the time

[is that my watch]

the low temp 3031 module. is the thing so ...

GLS-5600
G-7900
G-800BD
G-9000