RTD Input to Digital Conversion, Scale Units | Siemens 505-2557

1.2RTD Input to Digital Conversion

Engineering Units The following equations may be used to calculate the digital word in decimal format which will result from a particular RTD input:

RTD Mode, Digital Word (WX) = Degrees X 10

Millivolt Mode, Digital Word (WX) = Millivolts X 100

As an example, the following figure illustrates the effects of a change in input level going from 0 degrees to 102.4 degrees in the RTD Input Mode.

	Figure 1-2 Example Change Input Level
Scale Units	When data format is selected as SCALE the full temperature range of the
	RTD is scaled as an unsigned integer from 0±32000. The following formula
	may be used to calculate the scaled integer value:
	Scaled Integer = (measured temp ± min temp) ⎟(max temp ± min temp) ⋅
	32000
	For example the scaled integer offset at 0_C for a 100 Pt RTD is:
	Scaled Integer = 0 ± (±199.8) ⎟(849 ± (±199.8)) ⋅ 32000 = 6091

1-4

Description

SIMATIC 505±2557 Installation and Operation Guide

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Siemens 505-2557 installation and operation guide RTD Input to Digital Conversion, Scale Units

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 Community CE Agency ApprovalsEuropean Approval Description 100 Ohm, 10 Ohm, 120 Ohm RTDs, or Millivolt Inputs Operating Modes Word Input to the PLC from the Module RTD Input to Digital Conversion Scale Units Out-of-Range Input SignalsEffect Effect of Voltage Input 10 Ohm Copper Resolution Input Resolution Selecting 2 and 3 Wire or 4 Wire Operation Installing and Configuring the ModuleCalculating the I/O Base Power Budget Installing and Configuring the Module Configuring Millivolt Input Temperature orSelecting Fahrenheit Selecting DegreesCelsius or Selecting Data Configuration Jumper Locations Base InsertingModule Into Wiring the Input Connectors Copper Wire Table at 25 Degrees Celsius Press 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 Overview Advanced Software FunctionsIntroduction Advanced Jumper Setting the ModuleConfiguration Memory LoggingController I/O Input Registers Internal Register StructuresInput and Output Register Offsets Input Channel Data Input Flag Bits Peak/Valley Hold Input Words Output Data Registers Averaging Inputs Function Enable BitsControl Registers Discrete Handshake Inputs Outputs Data Identification Bits Loading Data into the Simatic 505±2557 Module Data Loading Process Sample 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 Considerations When UsingTiming Overhead for Functions Enabled Timing Constraints Default Function Values for Simatic 505±2557 Default ValuesDefault Function Values Additional Information about Each Function Centigrade or Alarm SetpointsDegrees Degrees Fahrenheit Digital Filtering Hold AveragingPeak and Valley Hold Reset Flag Bits Function Precedence Troubleshooting 10 Troubleshooting Flow Diagram Symptom Probable Cause Corrective Action I/O Register Quick Reference 17 I/O Register Quick Reference Or K Memory Configuration Tables Page Addressing Worksheet Items Unique to the Simatic 505±2557 Module 18 Open RTD Status Bits Troubleshooting Specifications Table B-1 Specifications Specifications subject to change without notice Jumper Settings Log Sheet Customer Response Business Reply Mail