Recorders

Recorders Definitation -: It gives graphical record of history of measurements of some physical events.

Necessity of RecordersTo have a permanent record for investigation.Recorder record electrical and non-electrical quantities as a function of time.Electrical quantities such as voltage, current can be recorded directlyNon-electrical quantities recorded indirectly using transducers.

Classification of RecordersRecorders

Analog Recorders It is used when whole system is analog type.

Digital Recorders It is used when system has a digital output

Analog RecorderGraphic Recorder : It display & store a pen and ink record of the history of some physical event.Oscillographic Recorder (UV Recorder) -: This recorder uses UV light as a source & paper sensitive to UV light is used for recordingMagnetic Tape Recorder : In this electrical input signal is stored in magnetic memory & this signal can be reproduced whenever desired

Graphic RecorderStrip Chart Recorder -: It records one or more variable with respect to time. It is an X-t recorder.X-Y Recorder -: It records one or more dependent variable with respect to an independent variable

Strip Chart RecorderGalvanometer Type Recorder -: It operate on galvanometer deflection principle. Null Type Recorder -: It operates on comparison principle.

Null Type RecorderPotentiometric Type Recorder

Bridge Recorder

LVDT Recorder

Types of Recorder (according to Points)Single Point Recorder -: It record only one measured variable, it draw single continuous curve.

Multipoint Recorder -: It record more than one variable upto six variable. It has maximum four pens, it has maximum 24 inputs, it has max. 6 colors

X-Y Recorder(Plotter)Definition X-Y recorder is an inst. Which gives a graphic record of relationship b/w two variables

First Method First variable control the position of the roll(paper)in Y-direction while second variable control the position of the recording pen(stylus) in X-directionSecond Method First variable moves the stylus in X-direction while another variable moves stylus in Y-direction at right to X-direction, here paper remain stationaryMethod of operation of XY-Plotter

X-Y Recorder

X-Y Recorder FeaturesIt have sensitivity of 10v/mmSlewing speed of 1.5m/sec.Frequency response about 6Hz for both axisChart size is 250*180mmAccuracy is about 0.3%

ApplicationsPlotting the curves of vaccum tube, zener diode, rectifiers etcSpeed torque curves of motorsResistance vs temp graphMechanical measurementsRegulation curves of power supply

XY recorder

XY recorder

Galvanometer type

Magnetic RecorderA magnetic Recorder is used to record data from electrical to magnetic form and retrieved or reproduced the same data in electrical form again and again

Magnetic Recorders

Type of magnetic RecordersThere are two types of magnetic recordersMagnetic tape recordersMagnetic disk recorders

FeaturesIt have a wide frequency range from DC to several MHzIt have wide magnitude upto 50 dbIt have low distortionIt stores electrical i/p signals in magnetic formIt reproduce signal from magnetic form to electrical signal

Features cntd.Magnetic tape/disk can be used to erase old data and reused to record new set of dataIt permits multi channel recordingData may be recorded as fast as speed of (1.5 to 3.05 m/sec)Data can be retrieved as low as speed of (4.76 to 2.38 cm/sec)Both analog as well as digital signals can be record.

Basic Components of magnetic Tape/disk RecorderRecording Head- The construction of magnetic head is similar to that of a transformer having a toroidal core with a coil. A fine air gap of length 5-15 micro meter is shunted by passing a magnetic tape/disk

Component cntd.Magnetic Tape/disk Magnetic tape/disk is composed of a coating of fine magnetic iron oxide particles (Fe2O3)on a plastic ribbon/disk. A typical tape is 12.7 mm wide and 25.micro meter thick. The magnetic particles conform to magnetic pattern induced in them and retain it.

Component cntd.Reproducing Head- The reproducing head detects the magnetic pattern stored on the tape/disk and converts it back to original electrical signal. The reproducing head is similar in appearance to that of a recording head.

Component cntd.Tape/disk Transport Mechanism- This mechanism moves the tape along the recording or the reproducing heads at a constant speed. The tape mechanism must be capable of handling the tape/disk during various modes of operation without straining, distorting or wearing the tape. This requires that the mechanism must use arrangements to guide the tape/disk to magnetic heads with great precision, maintaining proper tension and obtain sufficient tape/disk to magnetic head contact. Arrangement for fast winding and reversing are also provided.

Tape transport mechanism

Component cntd.Signal Conditioning Devices- These devices consist of amplifiers and filters required for modifying the signal to a format that can be recorded on a tape/disk, reproduced data from the tape/disk

Working of magnetic recordersWhen Magnetic Tape/disk is passed through a recording head, A recording current in the coil causes a flux of the same shape to bridge air gap and hence to pass through magnetic tape/disk, there by magnetizing the iron oxide particles as the pass the gap. The state of magnetization of the oxide as it leaves the air gap is retained, thus the actual recording takes place at the trailing edge of the gap. The same tape/disk when passed through a reproduce or playback head produce variations in reluctance of the winding there by inducing a voltage in the winding dependent upon the direction of magnetization and its magnitude on the magnetic tape/disk.

Methods of recordingDirect recordingFrequency modulated recording (FM Recording)Pulse duration modulation (PDM) Recording)

Direct recording It is simplest method of recording, usually required one tape/disk track for each channel. The signal to be recorded is amplified and mixed with a high frequency bias and fed directly to the recording head as a varying electric current.

Frequency modulated recording (FM Recording) Frequency modulation (FM) as the name implies uses the variation of frequency of carrier signal to carry the desired information instead of varying amplitude

Pulse duration modulation (PDM) Recording)Pulse duration modulation method of recording is allow simultaneous recording of large no. of slowly changing signals by using time division multiplexing (TDM)

ApplicationsIn Instrumentation systemsIn Banking sectorIn Music Industries etc.

Ultraviolet RecorderUltraviolet Recorders are basically electromechanical oscillographic recorderThis is a modified version of Duddels multichannel oscillographs

Ultraviolet Recorder

Ultraviolet RecorderThis recorder consist of no. of galvanometer (moving coil) elements mounted in a single magnet block which reduce the size and costIn place of white light UV light is used as a sourceA paper sensitive to UV light is used for producing a trace for recordingThe UV light is projected on paper with the help of mirror attached to the moving coil

ApplicationsUsed for signal dc & ac signal having fundamental frequency upto 400 to 500 HzRecording of high frequency i/p is possible if recorder with high paper speed of about 10 m/sec are availableIt is widely used as recorder for research and industry

Strip Chart RecorderIt records one or more variable with respect to time.

It is an X variable with respect to time recorder

Strip Chart Recorder

Strip Chart RecorderIt consist of a long role of graph paper moving verticallyThe speed selector of paper driving system is available with 1 to 100 mm/sec select manuallyStylus for marking is moving on graph paper, horizontally proportional to quantity being recorded

Components of Strip Chart RecorderPaper Drive SystemMarking Mechanism (a) Marking with ink filled stylus (b) Marking with heated stylusTracing Mechanism (a)Curvilinear System (b)Rectilinear System

Drawback of Strip Chart RecorderInk related problem in stylus i.e. viscosity, discontinuity, spottingAppearance of graph is depend on paper qualityIt unable to provide relationship b/w two variables

Strip chart type

Digital Data LoggerStrip chart recorder is replaced by digital dataloggerIt is an electronic device that records data over time with a built in instrument or sensor or via external instruments and sensorsThey generally are small, battery powered, portable, and equipped with a microprocessor, internal memory for data storage, and sensors

Digital Data Logger

Digital Data Logger

Significancedata loggers interface with a personal computer and utilize software to activate the data logger and view and analyze the collected dataOne of the primary benefits of using data loggers is the ability to automatically collect data on a 24-hour basis

SignificanceUpon activation, data loggers are typically deployed and left unattended to measure and record information for the duration of the monitoring period

ApplicationIt is used as a data acquisition systema comprehensive, accurate picture of the environmental conditions being monitored, such as air temperature and relative humidityUsed in ISRO, DRDO for data processing application

ApplicationsUnattended weather station recordingUnattended soil moisture level recording. Unattended gas pressure recording. Road traffic counting. Tank level monitoring. Water level monitoring for groundwater studies.

Referenceswww.google.comwww.wikiepedia.comElectrical & Electronics Measurement & Instrumentation By A.K.SawhneyMeasurement Systems, Applications & Design By E.O.Doeblin

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