Lake Shore Model 620/622/623/647 Magnet Power Supply User’s ManualOperation 3-93.6.3.2 DELAY SETUP SCREEN WITH DITHERINGTo access the dithering feature, turn ON (upposition) switch 5 of the rear panel CAL AND ID DIPswitches. Select DELAY/DITHER from FunctionMenu 3 to display the AUTOMATIC MODE DELAYscreen to the right.DITHER : XX SThe dwell in seconds for each of five dithering excursions from the desired Magnet End Current. Default = 60seconds.DITHER : + X.XX%The maximum dither excursion from the Magnet End Current in percent. Default = 0.5%.DITHER : To enable dithering, this must read . Move the cursor to the last line using the Up/Down cursor keys.Press either the Data Entry up or down key to toggle the Dither Feature on and off. Default is off.3.7 MANUAL PERSISTENCE CONTROL EXAMPLEAssume the magnet is in persistence with a current of 20 amperes. It is desired to change the magnet currentto 30 amperes and return to persistence mode.Connect the MPS to the magnet and the PSH heater terminals to the persistence switch. Turn on the MPSand set the PSH heater current to the desired current. See Paragraph 6.3.2 to set heater current. The Normalmanual screen displays (see Paragraph 3.3).First, ramp the MPS to the value of current in the magnet. Actually, MPS current flows in the persistenceswitch, not the magnet. As MPS current increases, the persistence switch current decreases eventually tozero. Select a suitable ramp rate for current in the persistence switch, enable the ramp if not enabled, andenter 20 amperes into the setpoint setting. The MPS ramps to 20 amperes. After settling, the MPS currentequals the magnet current, with zero current in the persistence switch.Using the cursor keys, move to the last line PERSISTENCE: and press a Data Entry up or down arrow.The heater turns on, and the changes to . If it does not change, check the heater wiring and/orheater current specified. If an error message **OUT OF CMPL** appears, then the heater power supply is atits voltage limit. If so, check the wiring, and/or change the heater current.At this point, the MPS and magnet currents are 20 amperes. Select a suitable ramp rate for current in themagnet and enter the desired current (30 amperes) into the setpoint setting. The MPS and magnet currentramp to 30 amperes.Using the cursor keys, move to the last line PERSISTENCE: and press a Data Entry up or down arrow.The heater turns off, and the changes to .Now ramp the MPS to zero current. The magnet is in persistence at 30 amperes. Figure 3-2 illustrates theprocess just described. The same process can be done automatically. See Paragraphs 3.5, 3.8.3.8 AUTOMATIC PERSISTENCE CONTROL EXAMPLE1. Enter the Instrument Setup screen and set theCompliance voltage limit which the MPScannot exceed. See magnet manufacturerinformation to determine this value. Once set,the MPS retains the value in non-volatilememory as the default value. Return to theAutomatic Mode display. 3 3 3 ( ( ( ( ( 2 8 - . / 0 1 , - . / 0 1 % & # 2 !
