3-42 BOP HIPWR 1113152. To return to digital or local control, from the power-up screen, press $, then highlight Ref-erence Input and press !. Highlight Internal and press $ to save. Then press % toapply the changes (without saving for power-up) and exit.NOTE: Each time the Reference Input setting is changed, the unit generates an internal *RSTreset command (see PAR. A.11) which requires the BOP output and/or protection limitsto be reprogrammed.For an external reference of ±10V, the nominal voltage gain (GNOM-V ) of a BOP 36-28MG is36/10 = 3.6. If the new full scale voltage for 10V is set to 29V, the voltage gain is changed from3.6 to 29/10 = 2.9. The gain can be changed from the front panel, but the output is controlled bythe external reference signal and can not be changed from the front panel.New Gain = New Full scale set at front panel / External reference that produces Full scale out-put. This means that the External reference voltage, from +10V to –10V, can control the fullscale output voltage from +29V to –29V. The gain range is between zero and the nominal gainof each model.Once the feature is configured, the new full scale value is entered by changing the active settingvalue of the main channel. This determines the full scale output to be produced by a 10V exter-nal reference.The gain in voltage mode is GV = VSET/10 where VSET is the desired full scale voltage (in Volts)entered at the front panel.The gain in current mode is G A = ISET/10 where I SET is the desired full scale current (inAmperes) entered at the front panel.NOTE: If the system limits have been modified (PAR. 3.3.4), the output of the power supply willnever exceed the modified system limits.3.4.4 EXTERNAL PROTECTION LIMITSWhen PROTECTION LIMIT on the Reference Menu is set to EXTERNAL, the protect limits aredetermined by four analog signals referenced to Ground (pin 12) which are applied to the Ana-log I/O Port (see PAR. 3.4.4).To be functional this feature must first be configured either from the front panel, or by sendingeither CURR:MODE:PROT EXT (see PAR. B.31) or VOLT:MODE:PROT EXT (see PAR. B.99).From the front panel power-up screen press $, and highlight Protection Limit. Press ! tomodify, then highlight External and press $ to save. Then press % to apply the changes(without saving for power-up) and exit.Only two signals are active, affecting the complementary protect channel, ±current protectlimit for voltage mode and ±voltage protect limit for current mode. A voltage between +1V and+10V at the following pins (referenced to Ground, pin 12) will control the corresponding protec-tion parameter between 10% of the nominal value (see Figure 1-3) and the corresponding posi-tive or negative nominal full scale value.• –I_LIM_EXT (pin 5) - This +1V to +10V analog signal sets the negative current protectlimit from 10% of the nominal value to –full scale current. +10V corresponds to ratedminimum (maximum negative) current (e.g., for BOP 36-28MG, +10V sets negative cur-rent limit to –28A).
