Chart Recorders and Strip-Chart Recorders

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Chart Recorders are data acquisition instruments used to generate a chart or graph of data versus time.

Features that chart recorders and strip charts offer include:

  • auxiliary outputs
  • user interfaces
  • communications with computers
  • application software
  • memory and storage functions
  • built-in transducers

Note: Simple (inexpensive) ink-chart plotters may offer none of the above features.

Common signal inputs for chart recorders and strip charts include:

  • DC voltage
  • DC current
  • AC voltage
  • AC current
  • frequency
  • charge

Common sensor inputs for chart recorders and strip charts include:

  • accelerometers
  • thermocouples
  • thermistors
  • RTDs
  • strain gauges or bridges
  • LVDTs
  • RVDTs

Specialized inputs may include:

  • encoders
  • counters or tachometers
  • timers or clocks
  • relays or switches

Common applications include:

  • temperature measurements
  • humidity measurements
  • chromatography
  • spectroscopy graphs
  • misc. plots generated from data acquired from lab/test equipment outputs

Common formats of chart-recorder output data include:

  • circular x-y plotter: rotate at constant velocity -- rotation time may span from minutes to days -- while variable(s) is (are) plotted radially (see image below). In an X-Y plotter two selectable variables are plotted against each other in rectilinear coordinates. Plotted variables may include mathematical functions of data input. Circular plotters are inexpensive (initially), compact-sized, and simple to operate. They require a continuous supply of ink pens and chart paper.
  • strip-chart: variables are plotted with respect to time, as the paper strip advances uniformly through the plotter. Strip often comes off a roll for space conservation. Require a continuous supply of ink cartridges and chart paper. The last two images show two strip-chart recorders from Yokogawa and ABB.
  • paperless: plots and trending recorded on to hard-disk or external computer. Graphs visible on video monitor.
  • video graphing: don't require paper or ink. Graphs visible on video monitor.
  • hybrid: combines features of strip-chart and paperless recorders. Yokogawa is an example of a manufacturer of hybrid recorders. The Yokogawa DR130 is an example of a hybrid recorder (see image below).

A recorder's performance is determined by the readability of the information on its printed chart. The DR130 from Yokogawa can record clearly, in 10 colors, data from all measurement points, at 2-second intervals. It has a variety of recording functions including analog trend recording over an effective recording width of 150 mm, recording of digital measured values, recording of various messages, zone recording, and partially compressed and expanded recording, thus enabling data to be read off speedily.

above: DR130 Portable Hybrid Recorder from Yokogawa.

Temperature Chart Recorder, -20 to +120 degrees F, 7 Day, 8-inch chart

above: Battery-powered Temperature Chart Recorder, -20 to +120°F, 7 Day, 8" Chart from Dickson.

The μR1800 is a small recorder with effective recording width of 180 mm. The recorder come in 1-, 2-, 3- and 4-pen models as well as 6-, 12-, 18- and 24-dot models. With our contact-free technology, these recorders have attained high reliability, and have a small case only 220 mm deep. Universal inputs such as DC voltage, thermocouple inputs, RTDs, and contacts can be accepted. Besides analog recording, measurements and scales can also be printed. With 5 × 7 dot matrix displays, these recorders offer you easy-to-view data. Data setting is interactive and can be easily done. The μR1800 can be used as monitoring devices or as quality control equipment in many applications such as process temperature monitoring, pollution control, construction, furnaces, and the fields of medical diagnosis and refrigeration.

above: The μR1800 is a small recorder from Yokogawa with effective recording width of 180 mm.

ABB Commander 250-mm Strip Chart Recorders: The Commander MR250 records from 3 to 12 process signals on a 250-mm wide chart. Recorder is designed for panel mounting and can be configured for a wide range of input types and chart speeds. The Commander PR250 records from 3 to 24 process signals on a 250-mm wide chart. The PR250 provides many advanced processing capabilities such as flow totalization, math blocks, logic equations, configurable displays, and full message printing. Recorder can be panel mounted or used as a portable recording device for field or industrial applications.

above: ABB Commander 250-mm Strip Chart Recorders

Specifications for strip charts and chart recorders include:

  • differential analog input channels: use the difference between two signals as an input; common mode is filtered out. Some systems offer differential inputs which are combinations of two single-ended inputs; here, twice the number of differential channels are available as compared to single-ended inputs.
  • digital I/O channels: Digital or discrete channels are used for low-level (on-off) signals used in applications such as communication, user interface, or control.
  • sampling frequency: frequency of the analog signal sampling and conversion to a digital value
  • resolution: "granularity" of the digital word representing the analog value. A ten-bit number contains 210, or 1024, increments. A 0-10V signal could therefore be resolved into approximately 0.01V increments. A 12-bit representation would be in 212 (4096) increments, or divisions of 0.0024V for the same signal. Each additional bit doubles the resolution, and one bit is required for the polarity (sign) of a number.
  • accuracy: depends on the signal conditioning linearity, hysteresis, temperature considerations, etc. Often noted as the percent full-scale of measurement range.

Links:

Wikipedia definition of Chart Recorder

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Updated: Thursday, January 18, 2024 11:10 PST