BOP HIPWR 111315 3-411. From the power-up screen, press $, highlight Reference Input and press !. HighlightExternal and press $ to save. Then press % to apply the changes (without saving forpower-up) and exit. NOTE: This setting can be saved for power-up only by using the pass-word-protected Power-up Settings menu (see {PAR. 3.3.7), otherwise internal referencesare used for both main and protection channels upon power-up.2. To return to digital or local control, from the power-up screen press $, then highlight Refer-ence Input and press !. Highlight Internal and press $ to save. Then press % to applythe change 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.When the external reference is used, the BOP functions as a power amplifier, amplifying theexternal reference at pin 11 to produce the output.The nominal (inherent) voltage gain of each model is calculated by (G NOM-V ) = E Onom / E REF.and nominal (inherent) current gain is (G NOM-I) = IOnom / E REF. Thus the nominal gain is the ratiobetween the nominal (rated) voltage or current (E Onom or IOnom ), and the external reference(E REF) used to produce that output.So for an external reference of ±10V, the nominal voltage gain (G NOM-V ) = E NOM-V /10, e.g., thevoltage gain of a BOP 36-28MG is 36/10 = 3.6. The nominal current gain (GNOM-I ) is INOM-V /10,e.g., the current gain of a BOP 36-28MG is 28/10 = 2.8.The external reference voltage may be d-c, a-c, or a combination of a-c plus d-c. The maximumfrequency of an a-c signal should be below the inherent frequency response of the BOP (2KHzfor voltage, 800Hz for current (see Table 1-2). For parallel or series combinations, the frequencyresponse is reduced as specified in the instruction manual included with the cable kit. A fre-quency that exceeds the bandwidth of the BOP will cause the output to be distorted.For linear response (input vs. output) the software limit (see 3.3.4.1) should be set to nominaland the maximum peak value (d-c plus a-c) of the reference signal must not exceed ±10V. If theinput signal exceeds the limit value (either ±10V if the software limit is set to nominal, or a lesservoltage for a user-determined software limit) clipping of the output voltage or current to the limitwill occur.NOTE: If the system limits have been modified (PAR. 3.3.4), the output of the power supply willnever exceed the modified system limits. E.g, for a BOP 36-28MG, if the system volt-age limit is modified to ±18V, applying a positive analog voltage to pin 11 that starts atzero and rises to +10V causes the output to rise from zero and reach +18V when theexternal reference reaches +5V. The output stays at +18V while the referenceincreases from +5V to +10V since the system voltage limits for this example are ±18V.3.4.3.2 VARIABLE GAIN USING EXTERNAL REFERENCE LEVELThe BOP can function as a variable gain power amplifier similar to the fixed (inherent or nomi-nal) gain amplifier as described in PAR. 3.4.3.1. The user can determine a new (lower) full scaleoutput value for the ±10V reference level (applied at pin 11, referenced to pin 10, of the AnalogI/O port) by configuring the Reference input as follows:1. From the power-up screen press $ and highlight Reference Input. Press !, highlightExtlRefLvl and press $. Then press % to apply the changes (without saving for power-up)and exit.
