Best device t0 plot Relati0n of tw0 vAriaBle
X-Y recorder is the best device to plot relation of two variable.It is an instrument which gives a graphic record of the relationship between two variables. In strip chart recorder, self balancing potentiometer is used and these self balancing potentiometer is used and these self balancing potentiameter plot the emf as a function of time. In X-Y recorder, an emf is plotted as a function of another emf. This is done by having one self balancing potentiometer control the position of the roll while another self balancing potentiometer controls the position of recording pens.
The marking mechanism in X-Y plotter may be
- Marking with ink filled stylus
- Marking with heated stylus
- Chopper bar
- Electric stylus
- Optical marking method
A signal enters each of the two channels. The signals are attenuated to the inherent full scale range of the recorder. The signal then passes to a balance circuit where it is compared with an internal reference voltage. The error signal (i.e the difference between the input signal voltage and the reference voltage ) is fed to a chopper which converts dc signal to an ac signal. The signal is then amplified in order to actuate a servo meter which is used to balance the system and hold it in balance as the value of quantity being recorded changes.
The action described above takes place in both axes simultaneously. And hence, we get record of two variable in same graph.