Recorders

Recorders gives graphical record of history of measurements of some physical events

Basic elements :

Paper chart to record informationStylus- writing instrument interfacing apparatus

RecordersInstrument records one or more parameters that change with respect to time. Self balancing or galvanometerOne or more parameters with respect to some other- XY recorder

FeaturesLimited freq. response dc 125 HzMech. Writing instrumentSome strip chart types- uses photo graphic plate few thousand Hz

Self balancing system

Self balancing system

Recorders- typeStrip chart XY plotter

strip chart recorder- self balancing

Strip Chart typeSignal conditioning to drive chart at desired ratedrives reversible motorEvent marker to mark edges of chart

Strip chart type

Galvanometer typeGalvanometer recorder are uses dArsonvals movementBut not sensitveCost and size advantages

Galvanometer type

Strip chartUsed to indicate, record & controlUsed in refineries, steel plants paper mills etc

XY recorderRelationship bw two variables pen moves in two axesPen clamped or by creating diff. Pressure to hold penExpensiveGives time base generator

XY recorder

applicationsPlotting Chara curvesSpeed torque curves of motorsResistancevs temp graph mechanical measurements

XY recorder

XY recorder

Sampling OscilloscopeGain band width relationship of vertical ampr limits freq range in conventional scopesHigh speed signal reduces image intensity for higher freq.

Sampling oscilloscopeSo e beam has to be accelerated to high velocity KE increases, to maintain normal image Increase in electron beam velocity easily achieved by raising the Voltage of accelerating anode e beam with high velocity- needs greater potential for deflection high demand on Vert. ampr.

Can be done by sampling- as in sampling oscilloscope

Sampling OscopeSampling pulse of short intervalWaveform point by pointUses a sample freq. 1/1000 of i/p

Block diagram

Sampling delays i/pAvalanche blocking oscillatorRamp & o/p of staircase generator compared send a pulse if both V are equalTime base adjustment on ramp generator & mag. On attenr

Sampling Oscilloscope

DSO Digital storage OsciloscopeConventional types uses storgae CRT2 guns writing and flood gunFlood gun supplies low energy electrons to store

Disadvantages of conventional type

Can store only for finite timeTrace not fine as ordinary CRtWriting rate is lessExpensive CRTOnly one image can be stored

A solution

DSO

DSOWave form , digitalized stored in digital memoryContinously displayedCan store as long as power applied to memory

DSO- Block diagram

Resolution 0f ADC 8 bit divides i/p to 256Uses flash typeInstead of 8 bit two 4 bit flash used

Very fast type Dso Uses analog type storageSingle pole double trow Fet switch

Option for pre trigger- helps to find failure

Alpha numeric display

Alpha nimeral displayKey board generates code- ASCIICodes given to i/p buffer drives chartacteristics5X7 LED displayRom 64X 5X7 = 2240 bits

5 X 7 LED display

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