Revisions: IC660BBA101A , IC660BBA101B , IC660BBA101C , IC660BBA101D , IC660BBA101E , IC660BBA101F , IC660BBA101G , IC660BBA101H , IC660BBA101I , IC660BBA101J , IC660BBA101K , IC660BBA101L , IC660BBA101M , IC660BBA101N , IC660BBA101O , IC660BBA101P , IC660BBA101Q , IC660BBA101R , IC660BBA101S , IC660BBA101T , IC660BBA101U , IC660BBA101V , IC660BBA101W , IC660BBA101X , IC660BBA101Y , IC660BBA101Z ,
|
|
RTD Input blocks monitor temperature inputs from Resistive Temperature Detectors (RTDs). Two RTD blocks are available: 115 VAC/125 VDC RTD Block(IC660BBA101) 24/48 VDC RTD Block(IC660BBA021) They are identical except for the power supply. Features An RTD Input block has six input circuits, in three groups of two circuits each. Group to group isolation is 300 volts. Each input can be used with platinum, nickel, or copper RTDs. Input data for each circuit is linearized according to the type of RTD selected. Input data is reported to the CPU in engineering units of tenths of degrees Celsius, tenths of degrees Fahrenheit, tenths of ohms, or counts. Additional configurable features include: Alarm thresholds RTD resistance Alpha type Linearization Input filter time RTD blocks are factory calibrated; there is no need for subsequent re calibration. In addition, the block s automatic diagnostics can pinpoint the cause of installation and run time errors: Input Short detection Internal Fault detection Wiring Error detection Open Wire detection Overrange and Underrange input indication High and Low input alarms Fault reporting can be enabled or disabled circuit by circuit. Compatibility These blocks are compatible with PCIM and QBIM modules. Hand held Monitor IC660HHM501D, version 3.5 (or later) is required. For a Series 90 70 PLC, the CPU may be rel. 1 (IC697CPU731 or 771) or later. The bus controller may be rel. 1 (IC697BEM731) or later. For a Series Six PLC, the CPU must be rev. 105 or later. For a Series Six Plus PLC, rev. 110 or later is required. The programming software must be Logicmaster 6 rel. 4.02 or later. For a Series Five PLC, the CPU must be rev. 3.0 or later. The Logicmaster 5 programming software must be rel. 2.01 or later. RTD Input (115V 50/60 Hz 125VDC, .1A Max) GEK-90486D-2 Chapter 14 RTD 6 Input Blocks 14-3 Block Operation For each pair of inputs, a multiplexer switches the A/D converter between the RTD inputs and internal reference resistors that are used for self calibration. The following diagram shows one pair of inputs. SIG Opto couplers isolate the control and clock signals; a small transformer isolates the circuit power. A synchronous voltage to frequency converter changes the measured signals to the proportional frequency sent via an opto coupler to the processor. The processor s frequency counter converts this synchronous frequency to a 16 bit binary number. The processor corrects each input measurement for lead resistance and for internal offset and gain drifts as it converts the input to an ohmic value. This value is either reported as is, or linearized according to the RTD type selected and converted to a value in degrees. The per channel update rate (input filter time) is preset. It may be 400, 800, or 1600 milliseconds. These selections provide 14, 15, or 16 bit resolution of the measurement. 14 14-4 Genius I/O Discrete and Analog Blocks User s Manual September 1993 GEK-90486D-2 Input Data Format Each bus scan, an RTD block broadcasts 12 bytes of input data. Each input consists of 2 bytes of data in the configured units (C, F, ohms, or counts). Appendix B shows reference usage for a Series 90, Series Six, or Series Five PLC. Byte # Except as noted on the next page, temperature data from an RTD block is never overwritten due to the presence of a fault condition. The data continues to change after a fault condition has been detected. Hand held Monitor Input Display The Hand held Monitor displays the configured unit values. The following example shows the Monitor Block screen with configured units of tenths of degrees C. REF 97 120 I I1: 150.0 C I2: 25.5 C > 14 GEK-90486D-2 Chapter 14 RTD 6 Input Blocks 14-5 Diagnostics Circuit diagnostics for RTD Input blocks are listed below. Active circuits can be configured not to send diagnostic messages to the CPU if a fault occurs. However, such circuits still respond to faults and report them to the Hand held Monitor. If the CPU requests diagnostic information from the block using a Read Diagnostic datagram, the block returns current diagnostics for all active circuits, including any with CPU fault reporting disabled. It will not return diagnostics from inactive circuits. It is necesssary to clear any fault that occurs to re-enable detection of that particular fault. For example, after a high alarm is reported the temperature may drop back to an acceptable level. The block continues to supply the actual temperature data. However, to re-enable high alarm detection, it is necessary to clear the existing High Alarm fault report. This diagnostic indicates an input circuit measurement below the minimum expected for RTD type. It may indicate a fault in the wiring or in the RTD. Instead of reporting the actual input value, the block uses the appropriate Underrange value (see below). An internal fault occurs if one or more of the internal auto calibration readings for a pair of channels is out of tolerance. When this fault occurs, the block reports a value of zero for each channel of the faulty pair. The block s Electronics Assembly should be replaced. A wiring error fault occurs if connections between the RTD and the block s Terminal Assembly are incorrect. The incorrect connections may cause faulty input data to be reported. Field wiring should be changed to match the wiring diagram indicated on the block s faceplate. The block reports an Open Wire diagnostic if there is less current than expected for the input type on that circuit. An Open Wire diagnostic may also mean that the input circuit excitation current is not present. The RTD may be missing or faulty, or the RTD is not connected to the block. The block sends an Overrange message if the Celsius or Fahrenheit input value exceeds expected maximum positive value (limits are 850C or 1562F for platinum, 250C or 482F for nickel, +3276.7C or +3276.7F otherwise). This only occurs when converting to units of temperature. The block sends an Underrange message if the Celsius or Fahrenheit value exceeds expected maximum negative value (limits are 200C or 328F for platinum, 60C or 76F for nickel, 3276.7C or 3276.7F otherwise). Individual low and high alarm thresholds can be configured for each input. If an input reaches one of its alarm thresholds, the block reports a Low Alarm or High Alarm diagnostic. The diagnostic is triggered upon reaching the limit and will not be repeated until circuit faults are cleared. Input Shorted Internal Fault Wiring Error Open Wire Overrange Underrange Low Alarm/ High Alarm 14-6 Genius I/O Discrete and Analog Blocks User s Manual September 1993 GEK-90486D-2 Field Wiring Terminals 5 through 32 are for wiring field devices. They accept AWG #22 to AWG #14 wires. Power Source Wiring For block power, connect an appropriate power source to terminals 6 and 7. For an AC block, connect the AC source to the HOT terminal and neutral to the NEUT terminal. For a DC block, connect the DC source to the DC+ terminal and the return to the DC terminal. The ground (GND) terminal (5) is for block safety. It is connected to the block chassis. Noise Suppression If noise spikes exceeding 4000 volts will be present in the system, additional noise suppression is needed to protect the block. This can be provided by physically separating and shielding the RTD input leads from any noise source. Each circuit also has a SHLD terminal for shield termination, if desired. This terminal is internally connected to the block chassis and to the input power safety ground terminal. Additional suppression can be provided by connecting three MOVs to the block; one for each pair of input points (inputs 1&2, 3&4, and 5&6 are pairs). For one point of each input pair, connect the MOV between the RTN and SHLD terminals. For example, connect: terminals 10 and 12 for input 1 terminals 18 and 20 for input 3 terminals 26 and 28 for input 5, shown below. Be sure the MOV leads do not cause shorts between any other wires. Wiring for Input Devices There are 4 terminals available for each input device: a SIG, RTN, REF, and SHLD input. Connect RTDs between the SIG and RTN terminals. The REF input is used for lead wire compensation of a 3 wire RTD. For a 3 wire RTD, connect the third wire to the REF terminal. For 2 wire RTDs, short the REF terminal to the RTN terminal. Features marked with an asterisk in the table are configured from the Program Block ID screen of the Hand held Monitor, as explained in chapter 3. The rest of the features can be configured either using a Hand held Monitor, or by sending a Write Configuration datagram to the block from the host. Before configuration begins, the block s features should be decided on and recorded on a copy of the Configuration Worksheet printed on the next page. |
|
