In this topic, you study the definition and theory of Recording instruments.
These instruments maintain a written record of the quantity under measurement. For this purpose, they have a pen (replacing the needle) and a paper (replacing the scale), the pen moves on the paper and draws a curve or graph. For example we have an instrument (load curve plotter) which can draw a load carve (load Vs time) of an installation. The paper may be removed and kept for record and another paper may be fixed on the instrument for another curve. Similarly a potentiometric type of recorder is used for monitoring temperature. Yet another example is ECG (Electrocardiographs) used by doctors to record heart beat. The graph can be put into the record file of the patient for later use. The Fig. 1.7. (a) shows an ECG machine and (b) its drive mechanism.
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(b)
Fig. 1.7. ECG Machine (Recording Instrument).