Strip chart recorder

Friday, 05 January 2007

A chart recorder is commonly used to provide a graphic record of transient phenomena. Chart recorders are used in various applications where it is necessary or desirable to make a permanent visual record of variable data. Process chart recorders are used wherever to some extent comprehensively controlled processes, for example in the chemical industry, have to be monitored on line. A strip chart recorder is often employed to provide a printed record, particularly for medical electronic devices. As data is output, a continuous stream of paper output is produced. Low cost strip chart recorders are often used to record the temperature of perishable cargo during its transportation. Although chart recorders of various types and sizes exist, the typical chart recorder moves an elongated web or strip of recording medium relative to a device which marks the recording medium in response to the variable data being recorded. Strip chart recorders are used to record variations in a sensed predetermined variable condition over a period of time. Graphic recorders for strip charts have been used in lie detectors and in the medical field to record the time variation of the human heartbeat and other physical parameters. Various kinds of recording media are known, including plain paper marked with a pen stylus and various coated recording papers marked by a thermal or electric spark stylus. Continuous-line chart recorders record the process data continuously using appropriately controlled recording pens. In the case of multiple line recorders, a number of process data are recorded simultaneously on one chart recorder. Process chart recorders, which record the measurement data as a function of time or as a function of other parameters, are arranged either at the location of the central control point or where it is possible to make a controlled intervention in the process.

A typical strip chart recorder includes a housing having a swing-out door hinged to the housing, a chart dispenser, a platen, means for advancing a chart from the chart dispenser across the platen, a transducer, and marking means coupled to the transducer, with the marking means being disposed for marking that portion of the chart that is being advanced across the platen. A stylus or pen driven by a galvanometer or torque motor is mounted in the housing with the stylus engaging a bearing surface on the housing. The door can be opened to permit a roll of paper to be inserted into the housing. The paper is drawn from the roll and trained around the bearing surface under the pen and thence leads out of the housing by way of driven rollers. The rollers are driven at a constant rate, while at the same time the torque motor responds to the signal to be recorded and drives the pen back and forth over the paper thereby imprinting a data trace on the paper. The motor typically is either a synchronous motor or a stepper motor actuated in response to a signal from an oscillator. A stepper motor advances the recording medium by a predetermined distance upon each step of the motor, and thereby is preferred for moving the recording medium at a fixed rate of speed in a portable strip chart recorder which is battery-powered. Strip chart recorders are used to record various time varying signals. For example, a strip chart recorder may be used to record atmospheric temperature, or it may be used with medical monitoring devices to record physiological data, such as the results of an electrocardiagram. Strip chart recorders provide a means of producing a permanent record of data for numerous uses. Moving pen strip chart type recorders have been extensively used in industry to produce representations of measured dependent variables as a function of an independent variable, usually time. In electric power generating plants moving pen recorders continuously monitor many of the parameters of power generation.

Strip chart recorders commonly use a paper supply that consists of a continuous web of paper that may be stored on a roll or stacked as connected sheets or pages. Individual pages may be conveniently separated by the use of perforations or tear lines. Chart recorders such as circular chart recorders have evolved from the use of purely mechanical configurations to low-voltage electronic versions. Recently, microprocessor based digital technology has been incorporated into chart recorders, thereby enabling the chart recorders to handle a large amount and variety of information in addition to the recorded signals. In a strip chart recorder a recording medium is advanced from a roll by a motor while a stylus produces a record on the recording medium of some variable that is being monitored. The recording paper typically is supplied in roll form to the chart recorder, which feeds paper from the roll at a selected linear speed past the marking stylus. The marked paper may then move past a display window or region for immediate viewing, and may thereafter wind onto a suitable takeup spindle for storage. Some chart recorders, such as EKG and other medical data recorders, dispense the marked paper for tearoff and immediate separation from the chart recorder. There are also chart recording systems in which paper having a dielectric coating is passed over a stationary recording head which includes etched styluses. The styluses are pulsed selectively by digital circuitry forming a series of dots on the coded paper. Such systems often require further processing of the paper after the action of the styluses thereon. Thermal chart recorders which utilize stationary thermal print heads for applying images to thermally sensitive paper charts have generally been found to be highly effective for recording many types of data. Thermal chart recorders are generally capable of generating high resolution wave form images and that because they include a minimum of moving parts they are generally less prone to mechanical failures than other types of chart recorders, such as those which utilize moving styli for applying markings to charts. As a result, thermal chart recorders have replaced moving stylus type recorders in some applications.

Related Information about Strip chart recorder