Industrial design and ergonomics - HP 1050 Series Liquid Chromatography System - technical

Hewlett-Packard Journal, April, 1990 by Raoul Dinter

"Those who want to be successful in international markets need well-designed products. However, design is more than just that, it is part of the product's quality, it communicates the company's basic values, and therefore it may be an important criterion in the purchasing decision for high-tech products."' One effect of changing social values is that users are increasingly more selective in their demands on the human interfaces of products. They require much more than just good styling. The challenge for the industrial design of the HP 1050 Series Liquid Chromatography System was to keep pace with this trend.

Customer visits played a major part in the industrial design investigation. By observing and interviewing users, we were able to determine our own instruments' weak points as well as those of competitive machines: the instruments were loud, maintenance was complicated, access to the inside of the instrument was difficult, the instrument required large amounts of bench space, compatibility with other instruments was low, the user interface was easily misunderstood. Combining this list of customer needs with the technical requirements of other engineers in the team, the industrial designers were able to develop several alternatives for the user interface.

We chose the HP guidelines for computer products as the basis for the industrial design of the HP 1050. This makes the HP 1050 stackable like HP desktop computer products. Stackability, however, required that the internal components be reorganized, since usually instruments of this sort are repaired or modified from the top, by removing the top of the case. The solution was to split the internal components into two separate areas: the electronics in the back in a card cage, accessible from the rear, and the mechanical components at the front, accessible by opening the front door.

To design a simple and common user interface, we aimed to standardize as much as possible, which of course required considerable effort in coordinating our activities. A cardboard model showed external dimensions and aided in estimating the amount of space required on the lab bench.

The realization of the concept had to meet not just the functional demands of the instruments. Many improvements to the front panel had to be made, since they were not covered by the guidelines. A few examples are given here.

The front panel consists of seven plastic moldings, six of which are common to all modules. The door is the only piece that differs from module to module. The keyboard is the only piece fixed by screws-two in all. All the others snap together. The door can be swung open to obtain access to the parts requiring maintenance or modification during operation. The keyboard assemblies for all the 205-mm-tall modules are differentiated by individual silkscreens bearing the module-specitic key functions only. The base of the keyboard is intended to act as a handle during transport and as a guide for the capillaries-the liquid connections from one module to the next. A similar treatment in the metal work at the rear means that the instrument can be lifted by one person, unaided.

A difficult problem was posed by leaks that may occur in any liquid chromatograph. Most instruments leave the solution of this problem to the customer. The HP 1050, on the other hand, offers a contribution to the safety and the organization of the instrument by enabling the operator to install capillaries in gutter-like channels, which collect any leaks and direct them to a waste pipe. The drainage system (Fig. 1) consists of a leak basin, a leak sensor, and vertical channels running inside the front panel of each module. A channel in one module directs liquid to the channel in the next lower module without the need for special adaptors, so that only the lowest module in the stack needs to be connected to an external waste pipe. Any of the modules can be placed at the bottom of the stack. These leak interfaces are easy to remove for cleaning, which may need to be done more frequently when using liquids with high concentrations of salts, which may crystallize out.

Ergonomics

A user interface can only be considered well-designed when it can be operated without error, quickly, and without personal danger. Two examples are worthy of mention with respect to the HP 1050. The opening in the side of the autoinjector module allows the injector to be loaded via robotics, for example the autosampler, but primarily this opening is for loading the autoinjector with the sample tray by hand. The tray is designed such that it always fits right the first time. It is keyed such that there is automatically only one way to lower it onto the spindle-in the zero starting point for subsequent rotation during sampling. This avoids incorrect mounting and prevents injuries. The wide opening in the autosampler and the tray's grip-fast handle avoid handling errors such as slippage or impacts while placing the tray in such a confined space.

The second example is the keyboard. We had to find the best compromise among several parameters. Every module can be installed at the top or at the bottom of the stack, can be installed on a high or a low bench, and might be operated by a tall (95%) or a short (5%) person, both of whom should be able to read the display. Different mounting angles were simulated in several tests of the keyboard and display (Fig. 2), as were different types of displays. The best combination was found to be a vertical vacuum fluorescence display with a blue/green filter and a touchsensitive membrane switch keyboard inclined at 1 0 degrees from the vertical. We decided to avoid using grey areas around the keys since we wished to give the impression that the keyboard would be simple to use (there are 35 keys in the confined space of each keyboard) and to reduce the likelihood of erroneous input. Conclusion