On this page we talk about the features common to most handheld computers, and begin to explain some of the trade-offs to be considered when chosing a model for a specific application.
The handheld computer - Overview
At first glance, a handheld computer may appear to be a smaller version of your desktop computer, or, more appropriately a smaller version of your laptop. In a very general sense that may be true, but there are a number of significant differences, which taken together, might suggest that a handheld computer is a very different beast from the desktops and laptops that we are familiar with.
Items that differ include: the screen size; the keyboard size; battery; requirement to survive rough treatment; touch sensitivity of screen; operating temperature range; ability to survive condensation; ability to read barcodes; ability to interface with different accessories; wireless connectivity; ergonomics; and weight.
We will address each of these in the following sections.
Screens at the time of writing are generally 1/4 VGA. This is a good bit smaller than 1/4 the size of most laptops and desktop computers. And these machines are often used in places where there is poor lighting, and sometimes movement. They are, after all, handheld devices. So care must be taken in screen design and layout to ensure that the user interface is effective. The most obvious trade off is between a small font, which gives lots of information, and a larger font, which is easier to read. Perhaps the ultimate handheld computer would automatically detect the users age, and adjust the font size accordingly!
One point to be aware of - small variations of screen size are of limited use. One machine offers an extra 30 pixels of screen down one side. The amount of engineering required to use that extra 30px is considerable, the benefit small, and the software from that point on in constant need of special maintenance, extra work with every upgrade. So unless you are deploying some hundreds of units, those extra few pixels may be of limited benefit.
A "key" issue (no pun intended). Much will depend on the way the machine is to be used. If most input is by scanning of barcodes, as in a mature asset management system, then keyboard function is less critical. But if there is significant mobile data entry, they a good keyboard is critical.
There are two considerations - the number of keys, and the size of the keys. There is little standardisatin in keyboard design. THe number of keys varies. And so does the layout - some opting for QWERTY, others for alphabetic. The size of the keys can vary from small sub-tic-tac size, to close to that of the a regular keyboard.
The trade-off always, is between ease of use and size. Again, the best option for you will depend on the way the machine is to be used. If the user must always have the machine with him, and the use of the unit is incidental to other tasks, then portability and small size are important. If the handheld computer is the prime tool of the user, if there is significant data entry, and some of that is alpha (as distinct from numeric only) - then a good keyboard is a mandatory requirement.
A personal view - don't be too concerned about keyboard layout. If this is going to be a key tool for the user, then any initial difficulty with the keyboard will disappear after a few days use. One of our clients, when first introduced to his handheld computer, almost refused to use it when he realised it had an alpha keyboard. Grudgingly he agreed to try it. When we returned two weeks later, they had fallen in love, and the user's fingers were a blur on the keyboard as he excitedly showed us some of the features he particularly liked. The initial difficulty was long forgotten. But again, managing that initial introduction is key.
Battery life is critical. If the battery does not last the shift, the machine, and perhaps the system, is useless. In a properly designed system, data will not be lost if the battery dies. But beware, we have heard too many horror stories of lost days and lost data (but only when our clients talk about their previous systems.)
Most units permit the battery to be swapped, and often provide charging arrangements for a second battery in the charging station. Battery life is affected by many factors, including screen brightness, scanning functions, and the use of accessories, particularly RFID. In olden days (c1990) even the use of add-on memory would reduce battery life, though that is not the case today. Another old myth is that of battery "memory". That was definitely true in olden days (1990), but seems to be not an issue today.
Many models of hand held computer offer an alternative high capacity battery. This can result in a "power bulge" on the back of the unit, that can be very macho, or very inconvenient, according to your personal taste.
Configuration of the system can be key. If accessories, such as radio and RFID readers, are not required, they should be switched off by the software application. We have seen systems where failure to do this results in u unneccessary problems with dead batteries.
Again, the trade off is weight, portability, and time between charges. But generally, with a properly designed system, battery life should not be an issue.
Requirement to survive rough treatment
The very nature of handheld computers is that they will be carried around, and therefore, inevitably, occasionally dropped. This is a forseeable circumstance and appropriate hardware should be chosen. The degree of ruggedness varies significantly, between models and manufacturers. One vendor assured us (and we have reason to believe them) that their product is good for a nine foot drop to concrete. We are less sure of their assertion that the competitors' product was good only for a drop of three inches to carpet. But you get the point, a big range in robustness. The issue to consider here is the consequence of failure. Once "almost" client selected a system (not from us) that used a consumer grade product to collect essential data from the work done by four men in a truck. If the unit fails towards the end of the day (which, in fact, it often does) the day's work must be repeated. We don't count that to be a good economy.
Touch sensitivity of screen
Another difference. An important feature of the handheld computer, as this is another tool to work around the small keyboard and lack of mouse. The touch screen and stylus go part way to replacing the mouse, but beware, the stylus can be too easy to lose. And tip: don't use a rusty nail when the stylus is lost. (Yes, it has happened). The screen is tough, but will eventually be damaged. And tip two - the screen can offer a "soft" keyboard, but in our experience it won't be practical for serious data entry. Likewise the miniature keyboard that appears waiting for your stylus. So touch screen good, but only for a few keys, along the lines of [yes] [no] [back] [exit].
Operating temperature range
Your desktop computer probably spends most of its life in a comfy office. Your laptop might spend the night in the trunk of your car, but will probably be in a cosy environment when it is being used. But the poor handheld computer may be left on the dashboard of your car (or truck) in the hottest part of the summer, or the coldest part of winter. Or in the freezer. And it will be expected to work as soon as it is turned on. Different models have different operating ranges. The most extreme can, with a very little care, cope with the full range of Canada's weather.
Ability to survive condensation
The flip side of temperature range, is change of temperature. Taking a unit from a cold freezer to a warm, humid summer office, can cause water to condense on the outside, and through any opening. Particularly a problem for units with a barcode reader or imager.
Ability to read barcodes
A natural partner for the mobile handheld computer is the barcode reader. This can be laser or imager. Each have their advantages, see more in the "Reader" section of this site. There are many different barcode symbologies, but most readers can cope with all the common ones, though some setting may be required. The setting of the readers can be arcane, a black art. We have a great deal of expertise in this field (and the scars to prove it).
Ability to interface with different accessories
The trade-off here is usually between sealing and flexibility. Consumer units do not have much in the way of interface. Mid level units often have significant capabilities. The top end units are often closed and factory sealed, to achieve the high standards required for resistance to dust and water penetration.
Can be many flavours: bluetooth; 802.11x; Cellular (CDMA, GPRS etc). The cellular connectivity will need local approvals, so be cautious of what you read on the web. Available in the US does not mean available in Canada.
Often a significant issue. Easy to see and understand. A unit which is light and easy to hold has great appeal, which is a serious issue when considering acceptance by the users. Should the unit have a pistol grip (some can be added or removed in the field). Does it have a holster?
Closely related to the above. Consider the weight with the extra battery and the bar code reader and whatever other extra accessories are to he added.
Carrying case or Holster.
In our view, not a trivial matter. This can make or break an implementation.
So that is our generic overview of handheld computers generally. We hope you find it useful. Contact us for more information.
© SageData 2006 Ottawa