Despite the observed deviations of the LGI operating characteristic from linearity with a pulsed supply, the pulsed supply mode can be used with pulses having long durations in the order of 1 to 10 msec where the departure from linearity is negligible, and with pulses having short durations in the order of 100 μsec which are more convenient from the viewpoint of the balancing circuit design. In this case it is recommended that the pulse duration should be stabilized to an error of about 1% and that a nonlinear scale be used.
A pratical investigation was carried out on the supply conditions of an LGI with current pulses of 1 msec duration. At a frequency of 50 Hz the average power consumption was reduced by a factor of ten. It proved possible to adjust the LGI brightness by varying the pulse supply frequency from 30 or 40 up to 250 Hz.
An investigation was also made of the temperature drift for the LGI's characteristic with a pulsed supply and a dc supply. The average temperature coefficient of the drift t.c.dav was found from the formula
For T2=−40°C and T1=+20°C and with dc,the t.c.dav=0.91·10−3K−1, and with the pulsed mode wheref=50 Hz and τp msec the t.c.dav=0.115·10−3K−1. It should be noted that besides a departure of the operating characteristic from linearity there exists among the drawbacks of the pulsed supply mode for an LGI some extra blurring of the column's boundaries on account of the short passage time for the discharge to remote portions of the cathode. As a result the total error for an LGI under normal conditions with a pulsed supply may be increased to 5% (with a dc supply it is 2%). Nevertheless, the use of the pulsed supply mode turns out to be sound practice in a number of instances (such as, for example, when there are substantial variations in the ambient temperature).
Current Pulse Temperature Coefficient Passage Time Total Error Pulse Mode
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