RECORDING INSTRUMENT.

Recording Instrument: A  relatively small numbers of recorders are used to record only the value of the process variables, a large number of these records flow with the total amount indicated by a mechanism.The majority of the recording instrument ae used for automatic control application, for this application,254(mm) to 304.8(mm) charts are the most desirable because of greater accuracy in reading and positioning the set point and a better opportunity of observing process trends. Recorder are available with one ,two, three, and four pens, Ink of different colours could be used and by using an eccentric scale which follow the time line of the chart and pointer on the pen arm .It is possible to have a combined recording and indication instrument. The use of a printer has been in used for so long that they are recently available with literally thousands of calibrations including those for a single variable and others multiple segments for two or more variables. The standard chart speed is the 24hrs revolution ,but many other speed and the required drive mechanism available. The drive mechanism may be electric, hand wound springs drive or pneumatically operated.