Vogt P18FXT, Service Manual

Page: 107 / 124

10TA Service Manual
10-3
OPTIONS AND ACCESSORIES
Notes
If you press SELECT and do not change a parameter by pressing the up or down arrow keys, the
DTP-3 automatically returns to displaying the line voltage in a few seconds.
The new settings are saved in permanent memory when the display returns to displaying the
line voltage. The new settings may be verified by pressing the select button to sequence
through the various parameters.
To prevent tripping on a 1 volt change, the DTP-3 automatically calculates cut-in voltages for the
return from undervoltage conditions. The cut-out voltage is always based on user voltage and
tolerance settings, while the cut-in voltage is 3% closer to the nominal voltage setting. This
quality is sometimes referred to as hysterisis. This is to help reduce oscillation that may occur
on weak power distribution system. When the load is switched off due to undervoltage, the line
voltage will increase. Without the hystersis, the monitor would switch the load back on, the line
voltage would again drop, and cause a continuous on-off-on cycling.