DR230/240 Hybrid Recorders In The Darwin *1 Series

KASAJIMA Yukinori² MIYAMOTO Shigenobu² MIYAHARA Kiyofumi² MORI Sadao²

We have newly developed the DR230/240 Hybrid Recorders so that they can measure up to 300 inputs of DCV, TC, RTD, AC, Strain, mA DC signals, and contact signals, at 0.5-second intervals. This paper describes the design features of these recorders.

1. DARWIN is a registered trademark of Yokogawa Electric Corporation.
2. Test & Measurement Business Division.

INTRODUCTION

Yokogawa Electric was the first Japanese company to develop high-performance and functionally advanced, microprocessor-based hybrid recorders for multipoint measurement. These recorders are now in wide use among a multitude of different users.

The DR230/240 hybrid recorders are instruments of the DARWIN data acquisition system series. These hybrid recorders come in two types: the stand-alone model that offers excellent operability and the expandable model that allows the number of I/O channels to be easily increased up to 300. The two different types enable users to build a flexible data acquisition environment, making the recorders more versatile in their applications. The DR230/240 hybrid recorders are displayed in Figure 1.

 

Figure 1 External Views of DR230/240 Hybrid Recorders

FEATURES

1. High-speed Scan
   The DR230/240 recorders can acquire data, perform computations and process alarms for a maximum of 300 channels at 500-ms intervals—quadruple that of the previous Yokogawa recorders. In addition, the expandable model has achieved a dramatic improvement in realtime monitoring.
2. A Wealth of Input Modules
   The input modules of DR230/240 recorders can deal with a wide variety of signals, including DC voltage; signals from thermocouples and resistance temperature detectors; contact signals; power signals; pulses; strain signals and DC current. These input modules may be combined in the same system. In addition, a universal module is available to enable measurement of both DC current and temperature using a single input module.
3. Increased Extendibility in Functionality
   The expandable model provides a high degree of freedom. Users can connect the model up to six sub-units using dedicated cables in order to achieve multichannel hybrid recorders according to their application needs. This flexibility also helps save on the amount of wires required. In addition, a maximum of six input modules can be connected to each sub-unit to provide a maximum of 300 inputs.
4. Compact and Lightweight
   The highly reliable mechanical sections are the result of remodelling the design of conventional models and design optimization using CAE-based analysis techniques. Wherever applicable, these sections use resin-molded components constructed using the latest molding technologies. The mechanical design has helped integrate individual parts into fewer functional parts, thereby reducing the number of components used, as well as the size and weight of the recorders.
5. Excellent Resistance in Harsh Environments
   Isolation is provided wherever necessary; between input channels, modules and units (expandable model). The range of ambient temperature is specified as -10 to 60° C (for panel mounting) for sub-units installed on the measurement site and as 0 to 50° C (DR240) for the recorder itself. These temperature ranges reflect the high reliability of the recorders and their high resistance in harsh environments.
6. Easy Operation
   The recorders are equipped with a large three-line VFD display, ensuring the visibility that monitors should provide. They can be operated interactively through the display. The various types of operations can be classified according to their frequency of use, thereby simplifying the routine operation procedure. The cassette-housed recording paper and ink ribbons, which have proved popular with users, also make handling easier.
7. Adaptability as PC-based DASs
   The DR230/240 recorders permit data to be recorded in real- time or saved to floppy disks (optional) so that they can also function as a PC-based data acquisition system (DAS). The application software available includes the basic software package that sets the defaults for measurement conditions and logs data and an enhanced data logging software package that provides the superior monitoring capability of a PC.
8. Compliance with Safety, EMI and EMC Standards
   The DR230/240 recorders comply with the following standards.
   CE certification
   EN61010-1
   EN55011 Group 1, Class A
   EN550822-2
   Other certification
   CSA1010
9. Application-specific Optimum Design
   The two models available differ in regard to the shape of their casing, their panel design and their resistance to harsh environments. The desktop model (DR230) is suited for research and testing applications and the panel-mount model (DR240) is appropriate for industrial applications.

HARDWARE CONFIGURATION AND OPERATION

Figure 2 Block Diagrams of DR Series Recorder (Expandable Model) and DS Series Sub-unit

System Configuration

Figure 2 illustrates the expandable model of the DR230/240 recorders and their sub-units.

The DR series hybrid recorder consists of a recording-and- display section, main control section, communication control section and an optional floppy-drive interface section. The recorder has one internal serial bus and two external serial buses (named Passport). Communication modules such as the GP-IB module are connected to the internal bus for handling by the main unit of the DR series hybrid recorder. The Passport interfaces are connected to the sub-units, as shown in Figure 2. A maximum of six sub-units can be connected to the recorder at distances as far as 500 m. The I/O modules are connected to the sub-units, allowing data to be sent to the recorder for recording and reading on the display. Each sub-unit consists of a main control section, a unit-to-unit interface section, and a section that interfaces with modules such as input modules. The sub-units and modules are designed for common use with the DA series of data acquisition units. The link configuration is also common in serial bus, enabling the system to be configured with flexibility.

The main unit of the DR series recorder uses ASICs printer- control to ensure the hardware copes with almost all of the processes involved in interfacing keyboard operations for recording and display. This design strategy has relieved the CPU load. Consequently, it has become possible for a single CPU to handle the entire range of recorder processes of the which more than one CPU was required for conventional recorders. This strategy has thus reduced the number of components required. In addition, the main control section of the recorder is configured so that the printer-control functions are isolated from the section internally. This design approach has enabled the DR series recorder to share most of its hardware configuration with the DA series data acquisition unit and the DS series sub-unit. This approach resulted in the improved reliability and maintainability of the DARWIN series data acquisition system as a whole.

Mechanical Sections

Figure 3 Framework, Chart Cassette and Printer Carriage

The following design objectives were adopted for the mechanical sections of the DR230/240 recorders.

1. High quality and reliability
2. Downsizing, along with weight trimming by adopting resin molding
3. Reduced number of components and shortened machining and assembly time
4. Reduced number of fastening parts, such as screws
5. Part assembly based on interlocking methods
6. Design with consideration to automated manufacturing

To achieve these design objectives, a move was made to adopt resin molding in the design of mechanical sections. Thus, this became the basic rule. The following subsections discuss the details of the major components of these mechanical sections.

Framework

The framework, which was a subassembly of many different aluminum fittings and brackets in conventional models, has been resin-molded into an integral structure. Figure 3 is an external view of the framework, chart cassette and printer carriage of the DR230/240 recorders. In order to resin-mold the framework, a CAE-based analysis was made to examine stress and deformation. Physical strains were found to arise when other mechanical parts are attached to the framework or when the framework is assembled onto the casing. The effects on recording accuracy due to deformation and other subjects were studied according to the results of the analysis. Following the study, a repeated evaluations were made on the effects of variations due to an aging operating environment, as well as on the maintainability and repeatability of the mechanical accuracy against deformation and the dimensional accuracy (30 μm maximum in part). This evaluation was done in order to select the required type of resin material. A further analysis was made of the flowability of the resin material which serves as a key factor in molding. Not until the results of all these efforts were known, was it possible to resin-mold the framework. Figure 4 shows an example of the results of stress analysis and Figure 5 an example of the results of flowability analysis.

Figure 4 Stress Analysis on Framework, Chart Cassette and Printer Carriage	Figure 5 Flowability Analysis on Resin-molded Framework

Chart Cassette

The chart cassette, which like the framework was formed using aluminum in conventional models, has also been integrated using resin molding. For resin molding, CAE-based stress and flowability analyses were also conducted. The following are the design objectives for the chart cassette.

1. For the increased inspectability of recording results, the design should allow the recording chart to be taken out of the cassette before it is all used.
2. No screws should be used for increased productivity and improved appearance.
3. The cassette should be small and rigid for increased operability.
4. The sprockets should be made movable in order to cope with the expansion/shrinkage of recording chart and ensure stable chart feed.

Printer Carriage

Figure 6 Enlarged View of Printer Carriage

In conventional models, the printer carriage was attached with a linear bearing and driven by a DC servo motor using a pulley and belt. The new models, however, use Yokogawa's own screw shaft and nut made from resin. This design change has made it possible for regular stepping motors to be used and achieve the required high levels of accuracy and reliability. In addition, this change has eliminated the need for pulleys, belts, linear bearings and belt-adjusting mechanisms, simplifying the hardware configuration. During the process of the design change, it was discovered that any existing resin material could not achieve the required dimensional accuracy and resistance to abrasion. Yokogawa therefore collaborated with materials manufacturers to develop the optimum resin material by repeatedly blending many different kinds of raw materials and evaluating the results. The screw shaft does not have the parting lines usually seen in resin molding, establishing itself as Japan's first "machining-less" screw (where, machining includes shaping). Using the optimum shaping and latest molding method, the carriage and main-axle bearing are aligned coaxial with each other to a tolerance of no greater than 0.01 mm. It is now possible to ensure the required precision (noted below) by assembling the carriage using the interlocking method only.

• 10- μm tolerance in pitch-to-pitch errors
• 0.1-mm maximum run-out accuracy per 320-mm overall stroke
• 200-mm/s carriage speed

As the printing head, the recorder uses a ten-color wire dot printing head with established reliability. Figure 6 shows how the carriage is fabricated.

Human-machine Interface

All parts of the display and operating sections have been resin-molded, adopting a screw-less construction in order to improve the appearance and the efficiency of the assembly. The human-machine interface of the DR240 recorder has been designed so that it can be opened/closed by swinging it vertically, making it easier to replace the ink ribbon. The display unit uses a large VFD consisting of one 22-character line and two 40- character lines. This easy-to-view, versatile display unit can show measured values for five channels at one time, as well as bar graphs and the statuses of alarm relays.

CONCLUDING REMARKS

This paper has discussed the features, configurations and components of the DR230/240 hybrid recorders. These recorders have superior expandability and efficiency, allowing them to cope with varying application needs. The adoption of molded components in these DR230/240 recorders has also resulted in high functionality and operability. They are the low-cost, high- performance hybrid recorders of the new generation. We expect the DR230/240 hybrid recorders will be applied in even more areas.

REFERENCES

1. Sato, T. and Takahashi, M. "Data Acquisition Units in DARWIN Series (in Japanese)," Yokogawa Technical Report, vol. 40, no. 3 (1996), p.95-98.