VXI VT1538A VRS Mode Input Operation SCP Channels 0 & 1 only, E1538A Input/Output Characteristics

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is to maintain a constant-level digital output while the input varies from millivolts to several tens of volts.

For simple sensing of switches and open collector logic devices, a channel’s pull-up resistor can be connected by closing its PU switch.

Figure 6. The E1538A Input/Output Characteristics

VRS Mode

Input Operation (SCP

channels 0 & 1 only)

When the VRS configuration switch is set to on, the input signal conditioning for that channel is changed to make it compatible with a typical variable reluctance sensor. The variable reluctance sensor is commonly used to detect rotational shaft position and/or velocity. Because the voltage output of a VRS is proportional to the rate of change of a magnetic field, different rotational velocities generate different signal amplitudes. The VRS-configured channel detects the negative going zero-crossing point of the signal. To minimize the effects of input noise, the zero-crossing detector can only be triggered if the positive-going portion of the signal exceeded an "arming" threshold. The arming circuit is reset when zero-crossing detector is triggered so it can’t re-trigger until after the signal exceeds the arming threshold again. The arming threshold tracks the positive peak input level and is 80% of this peak value. By sensing the "zero-crossing" point of the input signal, the VRS mode isolates signal amplitude changes from affecting signal timing.

Note VRS enable ON is not allowed if PU enable is ON.

At high rotational speeds, variable reluctance sensors can generate voltage levels over 100VAC. The VRS inputs must be protected against signal levels over 17.5 Volts. If your VRS will generate voltages over 17.5, you must provide a resistor in series with the VRS input. The user-supplied resistor, together with the VRS input’s 5.38K input impedance form a voltage divider that attenuates the input signal at the channel’s Hi input terminal. Use the

10 Agilent E1538A Enhanced Frequency/Totalize/PWM SCP

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Contents VT1538A VXI Technology, Inc Introduction Support Resources User’s and Scpi Programming Manual Page Agilent E1538A Enhanced Frequency/Totalize/PWM SCP About this ManualIntroduction Identifying the Plug-on Important Setting Configuration Switches Switch Location and Example SettingsInstallation Connecting To The Terminal ModuleRecommended Signal Connections E1419A Option 11 Terminal Module ConnectionsInput and Output Characteristics Recommended Connections and Voltage LimitsVRS Mode Input Operation SCP Channels 0 & 1 only E1538A Input/Output CharacteristicsProgramming With Scpi Commands Shows the VRS mode input characteristicsConfiguring I/O Direction Setting the Input Threshold LevelDetermining the Input Threshold Level Inppol NormReading Static Digital State To set channels 40 through 43 to input digital statesTotalize Positive or Negative Edge State Changes Init SENSDATACVT? @44About Period Frequency Measurements SENSDATACVT? @45 SENSDATACVT? @45 Agilent E1538A Enhanced Frequency/Totalize/PWM SCP Agilent E1538A Enhanced Frequency/Totalize/PWM SCP Sense Quadrature Position Sensfuncquad 0,@148,149RPS Example of Rotational Velocity Sense Sense Rotational VelocityControlling Output Polarity Output Static Digital StateVariable Width Pulse Per Trigger Variable Width Pulse Train PWM Variable Frequency Fixed Width Pulse Train FM Variable Frequency Square-Wave Pulse Train Rotationally Positioned Pulse Output Rotational Pulse Command Usage Algupdate Init Example of variable position, preset width RST Sensfuncrvel 12,MISS,@140Variable Position, Width Preset by Time Example of variable width by angle, preset position Example of variable width by time, preset position Fixed Position, Variable Width by AngleALGSCALAR’ALG1’,’Width2’,.010 Stepper Motor Control Use the command Stepping mode valuesSensfuncvolt @100 Full Step Mode, Full and Half Speed, 4-Channel Page RST and *TST important Scpi Command Reference Command Syntax For newer Units onlyCommand Syntax For newer Units only Discussed Parameters INPutPOLarityINPutPOLarity? CommentsINPutTHResholdLEVel? Level can be set to a resolutionINPutTHResholdLEVel Send with VXIplug&play Function hpe14XXcmdReal64Q OUTPutPOLarityOUTPutPOLarity? SENSeFREQuencyAPERture SENSeFREQuencyLIMitLOWer Related Commands SensfreqaperSENSeFREQuencyAPERture? Init SENSeFUNCtionCONDition Related Commands INPutPOLaritySENSeFREQuencyLIMitLOWer? SENSeFUNCtionFREQuency SENSeFUNCtionPERiodSENSeFUNCtionPWIDth SENSeFUNCtionQUADratureSENSeFUNCtionRVELocity RPS SENSeFUNCtionTOTalize SENSePERiodAPERture SENSePERiodAPERture? SENSePERiodLIMitUPPerInit SENSePERiodLIMitUPPer? SENSePERiodMODESENSePERiodNPERiods Related Commands SENSePERiodMODESENSePERiodMODE? Send with VXIplug&play Function hpe14XXcmdInt32Q SENSePERiodNPERiods?SENSePERiodRANGeUPPer RST Condition is Send with VXIplug&play Function hpe14XXcmd SENSeTOTalizeRESetMODESENSePERiodRANGeUPPer? SENSeTOTalizeRESetMODE? SOURceFMSTATeSOURceFMSTATe? Send with VXIplug&play Function hpe14XXcmdInt16QSOURceFUNCtionRPULse SOURceFUNCtionSHAPeCONDition SOURceFUNCtionSHAPePULSeComments Send with VXIplug&play Function hpe14XXcmd SOURceFUNCtionSHAPeSQUareSOURceFUNCtionSTEPper Relationship of minvel, and maxvel SOURcePULMSTATe Usage See Stepper Motor Control onSOURcePULMSTATe? SOURcePULSePERiodSOURcePULSePERiod? SOURcePULSeWIDTh33,554,430 to 33,554,430 SOURcePULSeWIDTh?SOURceRPULsePOSitionANGLe Usage SOURceRPULsePOSitionANGLe?SOURRPULseVARType SOURRPULseVARType? SOURceRPULseWIDThANGLe00000787 to SOURceRPULseWIDThANGLe?SOURceRPULseWIDThTIME SOURceRPULseWIDThTIME? Specifications General SpecificationsFrequency Measurement Pulse Width Measure Rotational Pulse Source