Siemens 505-2557 installation and operation guide Digital Filtering

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Digital Filtering	Digital filtering time is the settling time to within 1 LSB of the
	analog-to-digital converter on the module. (Often digital filtering is specified
	as a time constant in milliseconds. With a time constant specification, it will
	take the input 4 to 5 time constants to reach 99% of the final value.)
	The value entered is the actual settling time.

	NOTE: In the SIMATIC 505±2557 module, the value used in digital filtering
	is not a time constant but is the settling time for the system to reach the full
	resolution of the analog-to-digital converter (ADC).

	When filtering is enabled, the actual resolution of the module is a full 16
	bits. The filtering function performs a dithering operation for the least
	significant bits.
	Default Filter Settling Time If the digital filtering bits are enabled via
	the WY register and the Y32 output and no settling time values are written
	to the module, then the default digital filter settling time of 250 msec is
	automatically used.
	Filtering and Alarms If filtering is enabled, then the filtered data will
	be used for alarm comparisons; that is, the data will first pass through the
	digital filter and its associated settling time and then be compared to any
	low or high alarm setpoint. This prevents alarm conditions that are
	attributable to noise.
	Changing the Settling Time When new filter data is written to the
	module, the microcomputer must recompute the filter time constants. This
	operation takes 25 msec and no new data is written to the controller during
	this time.
	Numerical Range Values loaded into the module for digital filtering are
	expressed as 16-bit unsigned integers 0 to 65535 in units of milliseconds.

	NOTE: Signed integers will be interpreted as unsigned values.

SIMATIC 505±2557 Installation and Operation Guide

Advanced Function Programming 3-21

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Contents Simatic Copyright 1998 by Siemens Energy & Automation, Inc Manual Publication History List of Effective Pages Contents Iv Contents List of Figures List of Tables Preface Approval Agency ApprovalsEuropean Community CE100 Ohm, 10 Ohm, 120 Ohm RTDs, or Millivolt Inputs DescriptionOperating Modes Word Input to the PLC from the Module Scale Units RTD Input to Digital ConversionSignals EffectOut-of-Range Input Effect of Voltage Input 10 Ohm Copper Input Resolution ResolutionInstalling and Configuring the Module Calculating the I/O Base Power BudgetSelecting 2 and 3 Wire or 4 Wire Operation Installing and Configuring the Module Configuring Temperature or SelectingMillivolt Input Selecting Data Selecting DegreesCelsius or FahrenheitConfiguration Jumper Locations Inserting Module IntoBase Copper Wire Table at 25 Degrees Celsius Wiring the Input ConnectorsPress In Wiring Connector Wiring Diagram for 2, 3, or 4 Wire RTD Wiring Diagram for Millivolt Measurements Cable Grounding Example I/O Configuration Chart Advanced Function Programming Advanced Advanced Software FunctionsIntroduction OverviewSetting the Module ConfigurationJumper Logging Controller I/OMemory Input Channel Data Internal Register StructuresInput and Output Register Offsets Input RegistersPeak/Valley Hold Input Words Input Flag BitsAveraging Output Data RegistersFunction Enable Bits Control RegistersInputs Discrete Handshake Inputs Data Identification Bits OutputsData Loading Process Loading Data into the Simatic 505±2557 ModuleSample Low and High Alarm Setpoints Identifying the Data Being Transferred 11 Enabling the Functions Loaded Loading Programs into the I/O Module 13 Startup Relay Ladder Logic Page Timing Constraints When UsingTiming Overhead for Functions Enabled Timing ConsiderationsAdditional Information about Each Function Default ValuesDefault Function Values Default Function Values for Simatic 505±2557Degrees Fahrenheit Alarm SetpointsDegrees Centigrade orDigital Filtering Averaging Peak and ValleyHold Flag Bits Hold ResetPrecedence FunctionTroubleshooting Symptom Probable Cause Corrective Action 10 Troubleshooting Flow Diagram17 I/O Register Quick Reference I/O Register Quick ReferenceOr K Memory Configuration Tables Page Addressing Worksheet 18 Open RTD Status Bits Items Unique to the Simatic 505±2557 ModuleTroubleshooting Table B-1 Specifications SpecificationsSpecifications subject to change without notice Jumper Settings Log Sheet Customer Response Business Reply Mail