Paperless Recorders

What is a Paperless Recorder

A paperless recorder is a fixed industrial instrument that acquires one or more process signals, displays them on a color screen as scrolling trends, bargraphs, and digital readouts, and stores the values in digital memory instead of drawing them with ink on a moving paper chart. The term videographic recorder is used interchangeably, because the screen renders the data graphically the way a video display would, while the underlying measurement is performed by the recorder's own input modules wired to field sensors. Procurement orders, datasheets, and standards bodies all treat paperless, videographic, and graphic recorder as the same class of device.

Functionally a recorder does three jobs at once: it measures, it shows, and it remembers. The measurement front end conditions and digitizes the input. The display lets a local operator watch the process without a SCADA terminal, which is why recorders remain common on skids, in plant rooms, and in furnaces where a control screen is not nearby. The memory and archive function is the reason recorders survived the shift to networked control: they are the on-instrument system of record, capturing a continuous, time-stamped, tamper-evident history that auditors, quality engineers, and incident investigators can trust.

The lineage runs directly from the mechanical chart recorder. Strip-chart recorders pulled a paper roll under ink pens; circular-chart recorders rotated a disc once per day or week under a single pen. Both required someone to change paper, refill pens, and archive stacks of charts, and both were limited to a handful of slow traces. Paperless recorders, which became mainstream from the late 1990s as flat-panel displays and flash memory matured, removed the consumables, multiplied the channel count, and turned the record into a searchable digital file. Many vendors still size their displays explicitly to replace a given chart format: the Honeywell Multitrend GR markets its 12.1 inch screen as a replacement for 180 mm and 250 mm (7 inch and 10 inch) strip and circular chart recorders.

The class spans a wide capability range. At the compact end, a 4 to 6 channel recorder watches a single skid or oven. In the middle, panel-mount units of 12 to 48 channels cover a process line. At the top, a Yokogawa GX20 reaches 100 channels in the base unit and up to 450 with a large-memory option, accessing as many as 500 measurement and computation channels over the network, which puts it in the territory of a small distributed acquisition system. There is no single universal recorder: the engineering task is matching channel count, scan speed, accuracy class, environment, and compliance burden to the application.

Four engineering dimensions drive the buying decision and the total cost of ownership: the number and type of inputs, the sampling and recording speed, the accuracy and stability of the measurement, and the data integrity and compliance framework around the stored records. The chapters that follow take each in turn, because a recorder that is cheap to buy but cannot prove its data is trustworthy is worthless in a regulated or quality-critical loop.

Recorder Types and Form Factors

Paperless recorders are classified first by mounting and form factor, which is usually the most constraining decision because it is fixed by where the instrument has to live. The main families are panel-mount videographic recorders, field-mountable recorders, portable recorders, and headless modular data acquisition units. The table below contrasts the four, using representative series whose specifications are published by their makers.

Panel-mount videographic recorders are the default. They drop into a standard cut-out in a control panel or enclosure door and present a touchscreen of 5.5 to 12.1 inches. This family covers the widest channel range and the richest feature set, from the 10 to 30 channel Yokogawa GX10 up to the 100 plus channel GX20, the up-to-48-channel Eurotherm 6180A, and the 16 channel Honeywell Minitrend GR or 48 channel Multitrend GR. The front bezel typically carries an IP65 or NEMA-style rating so the display tolerates washdown, while the rear and electronics sit protected inside the panel.

Field-mountable recorders move the whole instrument out to the process. The ABB SM500F is notable as the first field-mountable paperless recorder, built in a fully sealed IP66 and NEMA 4X enclosure that can be wall-, pipe-, or panel-mounted and accepts up to 7 analog inputs. This form factor matters when running long sensor cables back to a control room is impractical or noisy, or when the record must be made physically at the measurement point. The trade-off is a smaller display (the SM500F uses a 5.5 inch 320 by 240 pixel color LCD) and a lower channel ceiling than panel units.

Portable recorders such as the Yokogawa GP10/GP20 and Honeywell eZtrend GR package recorder-grade inputs in a benchtop case with a carrying handle, for commissioning, troubleshooting, and temporary surveys where a permanent install is not justified. Headless modular data acquisition units such as the Yokogawa GM10 share the same universal input modules as the recorders but omit the local display, are configured from a PC or web browser, and scale to hundreds of channels; they blur the line between a recorder and a distributed logger, and suit applications where the data is reviewed centrally rather than watched locally.

A second axis of classification is the application grade. General-purpose recorders log process variables for monitoring and trending. Compliance-grade recorders add the secure audit trail, electronic signatures, and validated software needed for FDA 21 CFR Part 11 environments. Heat-treat and aerospace recorders add AMS2750 temperature-uniformity-survey credits and NADCAP support so the instrument can run and document a furnace survey directly. Choosing the wrong grade is expensive: a non-compliance recorder cannot simply be retrofitted into a validated pharmaceutical or aerospace process after the fact.

Universal Inputs and Signal Standards

The defining feature of a modern recorder is the universal analog input, a channel that the user configures in software to accept any of the common process signal types without changing the hardware. One universal module can mix temperature, pressure, flow, and status signals across its channels. The Yokogawa GX/GP 10-channel universal module, for example, measures DC voltage, thermocouple, RTD, and contact signals on a single card. The table below summarizes what a typical universal input accepts and the standards that govern each signal type.

Thermocouples are the most common recorder input. IEC 60584-1 defines the reference functions and tolerances for the standard letter-designated types: K, J, T, E, N, R, S, B, plus types A and C added in the 2013 edition. The tungsten-rhenium high-temperature type D is widely used but standardized elsewhere, not in IEC 60584-1. Each type covers a different range and environment. Type K (roughly -40 to +600 degrees Celsius in general industrial use, and higher with suitable sheaths) is the everyday workhorse; Type S and Type B (noble-metal platinum-rhodium) reach into furnace, foundry, and glass temperatures up to around 1,600 degrees Celsius. Because a thermocouple produces only a few tens of microvolts per degree, the recorder must perform cold-junction compensation at the terminal block, and that compensation error, typically 0.5 to 1 degree Celsius, often dominates the total temperature error.

RTDs, principally the platinum Pt100, are governed by IEC 60751, which fixes the resistance-versus-temperature curve and the tolerance classes over the -200 to +850 degrees Celsius range. The familiar accuracy classes are Class A at about plus or minus 0.15 degrees Celsius and Class B at about plus or minus 0.3 degrees Celsius at 0 degrees Celsius, with tighter and looser classes also defined. Recorders accept 3-wire and 4-wire RTD connections; the extra wires let the instrument measure and subtract the lead resistance so long cable runs do not add error. Pt100 has 100 ohms at 0 degrees Celsius and Pt1000 has 1,000 ohms, both with the standard 3,850 ppm/K temperature coefficient.

DC voltage and DC current inputs connect the recorder to transmitters and analyzers that already output a conditioned signal. Voltage is taken directly across high-impedance terminals over ranges from millivolts to several volts. Current, almost always 4-20 mA, is read as the voltage across a precision shunt resistor (a 250 ohm shunt converts 4-20 mA into 1-5 V), so a 4-20 mA transmitter for pressure, level, flow, or any other variable can be trended on the same recorder as raw temperature sensors. Contact and pulse inputs capture on-off status, alarm acknowledgements, batch start and stop markers, and totalizer pulses, letting the recorder document discrete events alongside the analog trends.

Module architecture matters for maintenance and expansion. Yokogawa, Honeywell, and ABB build their recorders around plug-in input cards, so a unit can be expanded or a failed card swapped without replacing the whole instrument, and high-speed cards can be mixed with standard universal cards in the same chassis. When specifying, confirm the exact thermocouple and RTD types supported, the number of channels per card, whether channels are individually isolated (important for sensors at different ground potentials), and the isolation voltage rating.

Data Integrity, Archiving, and Compliance

The reason a paperless recorder costs more than a generic data logger is the integrity of its records. In process monitoring this is a quality nicety; in pharmaceutical, food, and aerospace work it is a legal requirement. Data integrity rests on three pillars: how data is stored, how it is archived and moved, and how it is protected against tampering and proven authentic.

Storage begins in nonvolatile internal flash so that data survives a power loss. Capacities vary widely by class: the ABB SM500F holds 64 MB of internal flash, the Honeywell Minitrend GR ships with 1 GB expandable to 4 GB, and the larger Multitrend GR carries about 3.7 GB. Internal memory is a buffer, not the final home, so it is sized to ride out network outages and to hold data between archive cycles, with the recorder typically overwriting the oldest data once full unless configured otherwise.

Archiving moves data off the instrument. Recorders write to removable media (SD card, USB memory stick, or Compact Flash on older units) either on demand or on a preset schedule, and they additionally push files over Ethernet by FTP or SFTP to a server. Archiving over the network effectively gives unlimited capacity, because the instrument is no longer the storage ceiling. The Eurotherm 6000 series, for instance, archives to removable media and/or over Ethernet and can encrypt data in transit with SFTP to prevent interception or falsification of packets. The recorded files are stored in a secure, tamper-evident binary format that vendor software, such as Honeywell TrendManager Pro or the Eurotherm review tools, reads back and validates against alteration.

The table below maps the regulatory and quality frameworks a recorder may need to satisfy, with what each one demands of the instrument.

FDA 21 CFR Part 11 sets the criteria under which the FDA accepts electronic records and electronic signatures as equivalent to paper records and handwritten signatures. For a recorder this means a secure, computer-generated, time-stamped audit trail that documents the creation, modification, and deletion of records and configuration; unique user names and passwords with no shared credentials; role-based access; and electronic signatures on records. Critically, the recorder is only Part 11 ready out of the box. Full compliance is a property of the whole validated system, achieved by following GAMP 5 and keeping records ALCOA+. ABB, Eurotherm, Honeywell, and Yokogawa all offer extended-security or advanced-security firmware options for this duty. Common audit findings, such as disabled audit trails, shared logins, and backdated results, are governance failures, not hardware faults, which is why validation discipline matters as much as the instrument.

AMS2750, the aerospace material specification for pyrometry, governs the temperature uniformity surveys (TUS) required to qualify heat-treat furnaces for NADCAP-accredited aerospace production. Recorders such as the Honeywell Multitrend GR and the Eurotherm 6000 series carry AMS2750 TUS mode credits that let the instrument run the survey and produce the data file from which a report-generation tool builds the uniformity report. If your process touches aerospace heat treatment, this capability is not optional.

Key Specification Parameters

A recorder datasheet can list dozens of lines, but eight parameters drive the selection decision: channel count, input types, sample rate, recording interval, measurement accuracy, A/D resolution, display size, and communications. The table below compares four mainstream series on the headline numbers, drawn from each maker's published specifications, before the parameters are decoded one by one.

Channel count is set by display size and module slots, and ranges from a handful on a field unit to hundreds on a large panel recorder. The ABB SM500F field unit takes up to 7 analog inputs; the Eurotherm 6180A and Honeywell Multitrend GR each reach 48; the Yokogawa GX20 reaches 100 in the main unit and up to 450 with the large-memory option, plus up to 500 math and communication channels accessed over EtherNet/IP. Size for today's points plus realistic growth, but note that a live screen showing more than about a dozen traces becomes hard to read, so heavily loaded sites often split duties across multiple recorders.

Sample rate versus recording interval is the most misunderstood pair of numbers. Sample (scan) rate is how often the input is actually measured: 100 ms per channel on the ABB SM500F, a 125 ms total scan across up to 48 channels on the Eurotherm 6180A, and as fast as 1 ms with the Yokogawa high-speed module. Recording (storage) interval is how often a value, often a representative point or a min/max pair, is written to memory, and it is frequently set slower, from 100 ms to several minutes, to control file size. If you must capture transients such as inrush, water hammer, or fast alarms, specify the scan rate, because a slow recording interval will average the event away even when the front end samples fast enough to see it.

Measurement accuracy is stated as a percentage of reading or of span plus a fixed digit or microvolt term, separately for voltage, thermocouple, and RTD inputs, and is valid only inside a stated reference temperature band such as 23 degrees Celsius plus or minus a few degrees. Field-grade videographic recorders quote around 0.1 percent of span (the ABB SM500F is plus or minus 0.1 percent of full scale), while precision recorders reach into the 0.04 to 0.1 percent of reading region with low microvolt floors. For thermocouples, add the cold-junction compensation error, which often dominates. Always read the temperature coefficient and the cold-junction term, not just the headline figure, because ambient swings in a real panel can double the quoted error. A/D resolution, commonly 16-bit on universal modules such as the Yokogawa GX/GX20, sets the finest division the converter can resolve and underpins the accuracy spec.

Display ranges from 5.5 inch quarter-VGA panels on field and compact units up to 12.1 inch multi-touch screens on large recorders, and is often sized explicitly to replace a given chart format. Communications are the modern recorder's link to plant systems. Typical interfaces include:

• Ethernet with web server: remote monitoring from a browser, plus FTP/SFTP archiving, available across the GX/GX20, SM500F, 6000 series, and Trendview families.
• Modbus TCP and Modbus RTU: master or slave, for exchanging values with PLCs, DCS, and SCADA. Honeywell GR recorders support Modbus TCP/RTU master/slave.
• EtherNet/IP and OPC-UA: for tighter integration into automation networks; the Yokogawa GX/GX20 offers EtherNet/IP and an OPC-UA server option.
• Serial RS-232 / RS-422 / RS-485: legacy and point-to-point links still common on installed bases.
• Email and FTP on alarm: the recorder pushes notifications and data files automatically when an alarm or event occurs.

Two further lines deserve attention on any datasheet: the enclosure / ingress rating (an IP65 front bezel is typical for panel units, while the ABB SM500F is fully IP66 and NEMA 4X), and the cited safety and EMC standards. Recorders are designed to the IEC 61010 / UL / CSA electrical safety standard and the EN 61326 family for electromagnetic compatibility; the Yokogawa GX/GX20, for example, is CSA/UL certified to IEC 61010.

Selection Decision Factors

Translate the preceding chapters into a model by working through the decision sequence below. Most recorder selection mistakes come not from one wrong line item but from deciding form factor or accuracy before the compliance and signal requirements are fully understood. The eight steps below double as an RFQ template.

1. Compliance grade first: Decide whether this is general monitoring, FDA 21 CFR Part 11 / EU Annex 11 regulated, or AMS2750 / NADCAP heat-treat duty. This is step one because it constrains the eligible models and cannot be retrofitted into a validated process later. Specify the extended or advanced security option up front if the duty is regulated.
2. Form factor and environment: Panel-mount, field-mountable, or portable. Match the ingress rating to the location: an IP65 front bezel suffices behind a panel door, but a wet, dusty, or outdoor point needs a fully sealed IP66 / NEMA 4X field unit such as the ABB SM500F.
3. Channel count and input mix: Count the analog points (with realistic growth), plus digital, pulse, and math channels. Confirm the exact thermocouple types (IEC 60584-1) and RTD types (IEC 60751) you need, channels per module, and whether channels must be individually isolated for sensors at different ground potentials.
4. Sample rate and recording interval: Set the scan rate by the fastest event you must capture (specify a high-speed module if you need sub-100 ms), and set the recording interval by the resolution and retention your records require. Do not confuse the two.
5. Accuracy class: Match accuracy to the use. Process trending tolerates around 0.1 percent of span; metrology, custody, and survey work needs precision-grade reading-based accuracy and a low cold-junction error. Each accuracy tier raises price and may change the module choice.
6. Memory and archiving: Verify internal flash size for the worst-case network outage, the removable media type (SD / USB), and the network archive path (FTP / SFTP / server), plus whether transit encryption is required. Confirm the review software (for example Honeywell TrendManager) and its file-validation capability.
7. Communications and integration: List the protocols the plant needs: Modbus TCP/RTU for PLC and SCADA exchange, EtherNet/IP or OPC-UA for automation networks, web server for remote viewing, and email/FTP-on-alarm for notifications. Confirm master/slave roles and channel limits.
8. Total cost of ownership: Add purchase price, configuration and validation effort (significant for regulated units), spare input cards, media, software licenses, and the cost of an audit failure. A recorder that saves money up front but cannot prove its data integrity can fail an inspection or void a heat-treat qualification, dwarfing the purchase difference.

One last dimension is serviceability and lifecycle: plug-in input modules that can be swapped without replacing the chassis, firmware upgradability, local spare-card stock, and long-term software support for reading archived files. A recorder is a system of record that may run for 10 to 15 years, so the ability to still open and validate its files a decade later is part of the specification. The established lines, Yokogawa GX10/GX20 and GP/GM, ABB SM500F and ScreenMaster, Eurotherm 6100A/6180A, and the Honeywell Trendview family (eZtrend GR, Minitrend GR, Multitrend GR), all maintain documented modules, validation kits, and review software, which is why they remain the safe default for projects where the record must outlive the hardware.