There were times when recorders and dataloggers were used primarily for generating permanent records of low-frequency signals or a series of events. But today, advancements in data acquisition and storage technologies make it possible for us to capture perpetually faster signals and record them in denser memory devices.
As a result, drastic changes are taking place in the conceptual roles of datalogging and recording as well as in the implementation of these functions. The differentiation between them also is becoming blurred.
Originally, dataloggers were defined as equipment for numerical recording of selected quantities, and recorders were identified as analog devices making permanent graphic records. Today, most numerical data is not used in its raw form but is converted to graphical presentations. And many recorders convert input signals into digital form for printing or electronic storage.
“Recorders are becoming much more data-acquisition oriented as you not only want to record real-time signals on paper, but also to save the data for later use,” said David Kortick, product specialist at Astro-Med. “In addition, you want to see the signals in real time without running the paper. Many of today’s recorders make this possible with built-in waveform monitors.”
Frequently, it is desirable to display or print only a section of a waveform. Selective viewing or searching for particular waveform segments requires electronic data storage and processing capabilities provided by paperless recorders which now are available in a variety of forms. When needed, a PC printer can become a selective secondary recorder, taking the place of the conventional paper recorder.
“Paper recorders now represent approximately $600 million/year in sales worldwide but are beginning to lose market share to paperless recorders,” stated Paul Coughlin, product manager at Monarch Instrument. “Increased productivity is the primary reason since data files acquired by paperless recorders are readily transferable to PCs for post-processing, file searches, report preparation, and selective hard-copy printing.”
However, not everyone is endorsing a pure paperless recording trend. “There still is an addiction to recording devices that provide chart-paper or paper-tape hard copy of recorded events,” said Tobin Zech of the Technical Support Group at Soltec. “These paper records are proof that the event was monitored and provide a convenient method of viewing trends, albeit cumbersome, when long records are involved.”
The decision to select a paper or paperless recorder obviously cannot be based just on security-blanket considerations. A range of recording choices exists, and the marriage of data acquisition, datalogging, recording, and PC technologies has led to a variety of intriguing possibilities.
Recording Choices
Three classes of storage media have been used widely for datalogging and recording: paper to produce an immediate hard-copy display, magnetic media for long-record or long-term storage, and solid state for providing quick data access.
Common paper-recording methods include pens driven by galvanometers or servos and linear thermal arrays. Galvanometric systems cover frequencies from DC to 150 Hz and thermal array recorders up to 25 kHz.
Paper and colored ink pens are popular due to simplicity of use and color-trace differentiation. Thermal paper facilitates dot-matrix printing and high-speed paper movement but does not offer color opportunities. Pressure-sensitive paper is great for low-cost recorder designs and guarantees marking where unattended operation is a must. But again, no color differentiation is possible, and the paper is easily scratched during handling, commented Jorg Mahr of the Technical Support Group at Soltec.
Magnetic media is used in the form of tapes and disks. “Early data-acquisition systems relied on magnetic tape because it was a removable, transportable medium that stored high data volumes at high speeds at an economical cost per bit,” said Richard Bond of Racal-Heim Recorders. “Tape technology has advanced so much that, despite the emergence of other removable media and solid-state technologies, the tape’s desirable qualities keep it a preferred media for many applications.”
Current implementations include purpose-designed drives such as Inter-Range Instrumentation Group (IRIG) drives, adaptations of commercial drives like VHS and S-VHS and computer drives such as digital audio tape (DAT) and 8-mm. DAT recorders are reliable and often used as a backup to other methods of recording,” said Bill Harrison, applications engineer at Nicolet Technologies. “They tend to be small and quite portable, which also makes them well suited for field use.”
“The shortening life cycle of media formats can present a major hazard to anyone preserving and accessing data over many years,” commented Racal’s Mr. Bond. “For instance, although the IRIG instrumentation format that originated in the early ‘50s still is alive today, other well-known computer tape or disk formats have come and gone within the last decade.”
The decreasing cost and increasing storage capacity of hard disk drives make them a serious competitor, and potential successor, to tapes—for all but high data-content or permanent-record storage applications. For medium data-content storage, floppy disks and PCMCIA cards offer convenient low-cost media. The declining cost of solid-state storage (battery-backed SRAM or DRAM) has made them an ideal choice for high-speed or intermediate-term data storage.
Configuration Choices
With the superb performance/price ratio offered by today’s PCs, it is only natural that they are in the forefront of all data processing, display, and storage-related applications, including datalogging and recording. A variety of embodiments exists, and new ones are constantly emerging.
For instance, integrated systems containing a built-in PC, printer, and monitor feature fast sampling rates, good display functions, and easy analysis. “These systems accommodate long record lengths and perform signal-conditioning, acquisition, real-time and post-run analysis, and custom reporting all out of one box,” said Nicolet’s Mr. Harrison. “Being fully integrated, they are somewhat large and generally not thought of as portable, but they often are used in the field.”
A widely used configuration inspired by data-acquisition professionals uses a PC plug-in card for signal conditioning, filtering, and multiplexing as the datalogger front end, the hard drive as the paperless recorder, and the monitor as the display. Permanent records of raw or processed data may be printed or stored on floppy disks, PCMCIA cards, removable cartridges, or tape.
Another common implementation uses an external box containing a degree of intelligence to suit a selected set of targeted applications. Data is transferred to a PC card or a PC port via a proprietary or a standard communication scheme such as RS-232, the Universal Serial Bus, or Ethernet.
Datalogger front ends containing little or no intelligence also are popular and cost-effective for many applications. These units primarily are scanners providing signal conditioning, thermocouple cold-junction compensation or strain-gage transducer excitation, and multiplexing circuitry. A laptop may be used for channel setup and control of the data-collection sequence, or setup and data-download may be accomplished via PCMCIA cards.
“Hand-held, multimeter look-alike dataloggers also have deluged the market to provide convenient in-field data-taking, either attended or unattended,” commented Soltec’s Mr. Zech. “In addition to uploading data to a PC, some of these dataloggers provide remote transmission via modem or LAN similar to their larger counterparts.
Many of these are application-specific and may not include any controls. In these cases, a temporary PC connection is required to load the setup information or to upload collected data.”
Naturally, there is a continuing need for conventional dataloggers and strip-chart recorders. To satisfy these demands and simultaneously provide PC links, several companies offer analog pen-and-ink recorders equipped with A/D converters and digital media storage. Conversely, many integrated digital dataloggers/recorders contain built-in mechanical or thermal strip-chart printers.
While the classic chart-paper amplitude-vs-time format is all that is needed for many applications, digitally recorded information can be easily processed to generate alternative, sometimes more meaningful, displays. Also, as more data is being generated, it becomes necessary to search for, separate, process, and display only a significant portion of the collected data.
All these search, processing, display, and recording capabilities are readily provided by today’s PCs. So, it is not surprising that, while hard-copy records of raw data or processed results always will be required, many of these will be produced via initial paperless digital recording aided by PCs.
Recorders/Dataloggers
Scope/Recorder Features
Built-in Signal Conditioning
The Integra 20 Four-Channel Digital Oscilloscope/Transient Recorder combines 12-bit digitizers with a color display and high-resolution analysis capabilities. It provides direct-to-hard-disk recording speeds of up to 100 kS/s for up to 40 min of continuous acquisition. True dual-time bases offer slow-fast-slow acquisition and independent sampled data sets with time correlation. Built-in signal conditioning allows the most common sensors to be connected directly to the unit. Data can be written to an integrated thermal writer. $11,500. Nicolet Instrument Technologies, (608) 276-5600.
Paperless Recorder Supports
One to Six Analog Channels
Data-Chart® 3000, a paperless recorder, supports up to six analog inputs and displays up to 12 channels of information on a 5″ LCD. It accepts a variety of inputs including DC voltages and currents, thermocouples, RTDs, and pulse signals. Touch-screen control facilitates selection of signal scale factors and record and analysis functions. Data is stored on an internal buffer and simultaneously on a PCMCIA card or a floppy disk. The recorder computes multiple math functions and provides 48 alarms. Starts at $1,325. Monarch Instrument, (603) 883-3390.
Data Recorder Stores
To PCMCIA Card
The T-Corder Model 510 Solid-State Data Recorder accepts analog and digital inputs and stores information on a removable PCMCIA memory card. The recorder measures and processes variables relative to the built-in real-time clock. It recognizes and handles signals such as voltage, temperature, pressure, strain, rotational speed, pulse counts, and switch positions. The T-Corder may be operated in a stand-alone mode or while connected to a host PC. From $1,745. Vulcan Enterprises, (602) 759-1600.
Eight-Channel Field Recorder
Has DSP-Based Filtering
The Dash 8 is an eight-channel field recorder featuring a 10.4″ active color LCD, an internal 1-GB hard drive, DSP-based filtering, and a built-in 100-MB removable Zip drive for data transfer and archiving. An input range extends from 50 mV to 500 V peak, and it records voltage, current, temperature, strain, and pressure gage signals. It displays and records eight channels of real-time data at frequencies up to 2 kHz. $9,950. Astro-Med, (800) 343-4039.
Light-Weight Recorder Suited
For Long-Record Applications
The OR100 “Handy OR” Oscillographic Recorder has two or four isolated inputs with ranges extending from 100 mV to 1,000 V and eight logic inputs. The internal memory capacity is 128 k/ch (512 k/ch interleaved) plus 40-MB mass storage. Data is sampled at 400 kS/s with a bandwidth of 100 kHz and stored to memory or printed. A PCMCIA slot can accept a mass storage card. With a fax/modem, the recorder can send waveforms-on-trigger and transfer files or receive settings from a PC. Starting at $2,100. Yokogawa Corp. of America, 800-258-2552, ext. 577.
Data Acquisition Recorders
Offered in Three Versions
Available in four-, six-, or eight-channel versions, the BD 300 Data Acquisition Recorders can be programmed to measure voltage, current, temperature, and frequency. Logging rates extend up to 100 Hz/channel. Data can be recorded in real time on the 250-mm width recorder chart, logged to the optional MS-DOS compatible disk drive, or transferred via RS-232 to a PC for post-processing analysis and playback. Inputs are connected via the detachable input backpack. Call company for price. Kipp & Zonen, Division of SCI-TEC Instruments (USA), (800) 645-1025.
Datalogger With Laptop/PC
Controls 10 To 230 Channels
The Model UCAM-20PC is a datalogger without data keys or displays. The dedicated 10- to 30-channel scanner base unit connects to a laptop/PC for interactive setup and control of measurements. All operations are controlled via the PC, including setting measurement conditions, collecting measured data, and filing and graphing stored data. To expand beyond the 30-channel measurement capability, additional scanner units can be attached for up to 230 channels of data collection. 10-channel: $9,995. Soltec, (800) 423-2344, ext. 421.
Datalogging System Features
Icon-Based Windows Software
The MiniLogger™ Portable Data Logging System has four analog input channels, a digital input channel, and four alarm outputs. It can be configured for six types of thermocouples, 11 DC voltage ranges, and five DC current ranges. The Hyperware™ for Windows icon-based communication and graphing software package implements logging and alarming strategies, real-time trending of monitored data, and multiple logging capabilities. The combined hardware/software datalogging system monitors flow, temperature, pressure, and process data. $995. Logic Beach, (619) 698-3300.
Recorder Stores Data
On 3½” Disk, PCMCIA Card
The new RD850/840 Series Paperless Recorders provide 14-bit resolution and offer up to 12 channels of analog inputs such as DC voltage, DC current, and thermocouple, RTD and pulse signals. Information is displayed on a bright, high- resolution, backlighted LCD, and data is recorded on removable 3½” disks or PCMCIA memory cards. Direct data transfer to IBM-compatible PCs also can take place via an addressable RS-485 or RS-232 communications port. $1,824. Omega Engineering, (800) TC-OMEGA.
Shock Recorder
Weighs Only 7 Oz
The SnapShock-PLUS Series Data Recorders measure and record peak shock levels, velocity change, duration, and date/time of transient acceleration events. The recorders feature a built-in single- or tri-axial piezoresistive accelerometer; signal conditioning with user-selectable filtering; 12-bit, 1,200-Hz digitization; nonvolatile on-board storage for up to 5,900 readings, and a real-time clock. Data is recovered via an RS-232 interface to a PC. It comes with Windows 95-based software for turnkey setup, data recovery, and analysis. Call company for price. Instrumented Sensor Technology, (517) 349-8487.
Six-Channel Recorder
Stores Data on Digital Tape
The Racal-Heim DATaRec A60 is an entry-level, dedicated, six-channel DAT/DDS-2 (digital audio tape and high-density tape) recorder designed for portable or stand-alone use. It accepts analog and digital inputs, has a 125-kHz system bandwidth, and provides two or more hours of continuous recording with >90-dB S/N ratio and better than 1° phase accuracy between channels. Each channel is compatible with conventional voltage and common sensor inputs and has user-selectable bandwidth. A built-in display allows record- and replay-monitoring. $11,300. Racal Recorders, (800) 847-1226.
System Streams Data at a
5-MS/s
Rate to SCSI Hard Disk
The GageStream 512 Data Acquisition/Recording System consists of a CompuScope 1012/PCI 12-bit A/D card, a PCI-based industrial-grade computer powered by a Pentium 133 CPU, a high-speed SCSI controller, and a 2-GB SCSI disk drive. The system features an oscilloscope-like analog front end and has internal or external trigger capability. An on-board, high-speed FIFO streams data to the SCSI card, even during bus latencies. GageStream software sets operating parameters. $14,995. Gage Applied Sciences, (800) 567-4243.
Recorders Provide a Range
Of Features and Flexibility
The DL250 Data Recorder integrates the functions of a datalogger, a multipoint recorder, an alarm annunciator, and a digital indicator. With a few keystrokes, operational parameters such as input types, alarm setpoints, chart speeds, and math calculations can be changed. Any combination of thermocouples, RTDs, current, and voltage may be monitored simultaneously. The DL250 is available in 16-, 32-, or 64-channel input-capacity configurations, each providing up to 10 programmable color traces and scales. Available interfaces include a standard RS-232-C and an optional RS-485. From $5,830. Gould Instrument Systems, (216) 328-7000.
Stand-Alone Dataloggers
Work With Most Sensors
The stand-alone, solid-state Datataker Data Loggers operate independently of a computer and offer up to 30 inputs. Collected data can be downloaded to a computer via RS-232, modem, radio link, or memory card. Data is stored in battery-backed RAM (13,650 readings) and Type 2 PCMCIA memory cards which store an additional 34,000 readings. Windows-based software is included. Digital outputs control equipment or raise alarms in response to input conditions. All data is in engineering units. From $2,975. Keithley Instruments, (888) KEITHLEY.
The DataMAX Instrumentation Recorder collects data on up to 64 channels. It features 90 kHz of analog bandwidth, a 90-dB dynamic range, and 1-GB to 100-GB storage capacity. The acquisition platform includes a Pentium 133-MHz processor, 16 MB of RAM, a color LCD monitor, a 3½” floppy drive, a 1-GB program disk, and an 8-GB tape backup. The recorder performs high-speed continuous acquisition, offers Windows NT control, and is network ready. From $25,000. R.C. Electronics, (805) 685-7770.
Data Acquisition Terminal
Includes Micro-Computer
The ASC Hand-Held Data Acquisition Terminal offers micro-computer communications and processing capabilities for portable data entry, instrumentation monitoring, and remote datalogging in industrial, laboratory, or mobile data-collection applications. It features multiple analog/digital transducer inputs and manual keyboard entry functions with an integral alphanumeric data display. Up to eight analog and eight digital input signals can be applied. Optional accessories include a portable printer, a tape recorder, a bar-code reader and a magnetic card reader. From $999. ASC Systems, (313) 882-1133.
Transient/Static Recorder
Is Rugged and Portable
The rugged, portable MEGADAC Digital Transient and Static DAS Recorder contains an on-board signal-conditioning system for transient and static digital recording. It features up to 300 input and 128 output channels, 16-bit A/D converters, and 4 MB of battery-backed memory (256 MB optional) and has a throughput rate of up to 25,000 S/s (250,000 S/s optional). MEGADAC I/O modules are field changeable and available for almost any transducer. The TCS software runs on Windows 95 and Windows NT. From $12,995. Optim Electronics, (301) 428-7200.
Acquisition/Switch Instrument
Has Datalogger Functionality
The HP 34970A offers 11 built-in measurements with internal signal conditioning. Per-channel configurability allows you to set scale factors, alarm limits, and measurement functions independently. The stand-alone instrument features 50,000 readings of nonvolatile memory. It includes Benchlink Data Logger software (Microsoft Windows 3.1, 95 and NT compatible) to configure, display, analyze, and archive data on a PC. Three slots accept any of eight add-in switch and control modules. From $1,190. Hewlett-Packard, (800) 452-4844, ext. 5089.
PC-Based Instrument Offers
Paperless Chart Recording
Expandable to 128 channels, the ChartScan/1400 Paperless Chart Recorder scans up to 147 channels/s in DC and thermocouple applications and performs AC true-rms measurements at a 20-kHz rate. Interchangeable 16-channel scanning modules are offered with BNC or sub-mini plug connectors, safety jacks, or terminal blocks. Data is streamed to a PC’s hard disk in real time via an RS-232 interface or modem (IEEE 488 or RS-422/485 optional). It comes with the Out-of-the-Box ChartView software package. IOtech, (216) 439-4091.
Hand-Held Datalogger Accepts
Multiple Input Modules
The MMS 3000 Multi Measurement System is a hand-held datalogger that accepts a variety of inputs via a range of plug-and-play modules. Data is stored in 128 kB of nonvolatile memory and displayed on a 240 × 128 pixel graphical display screen. Standard modules are available for measuring temperature (six channels), vibration, power, humidity, flow, pressure, displacement, and voltage. The datalogger may be programmed by connecting it to the PC’s serial port. Commtest Instruments USA, (805) 273-6597.
Copyright 1997 Nelson Publishing Inc.
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Instrumentation Recorder
Features Windows NT Control
October 1997