Triguard SC300E MHB44IND Pulse Input and Analogue Output Module (MHB44IND) Issue 2 October 2005 INTRODUCTION PURPOSE The MHB44IND module (Figure 1-1) supports four pulsed voltage inputs for interfacing with field detectors, and supplies 0 - 22mA analogue outputs for process control. The module is a rack mounted, 9U high unit that provides the output control interface between the SC300E processing environment and the user field environment. It has four current loop output channels.
Triguard SC300E 2 MHB44IND October 2005 – Issue 2
Triguard SC300E MHB44IND Pulse Input and Analogue Output Module Mechanical coding block (Upper) Links JP1 to JP4 Links LK1 to LK3 Connector J1 CommonInterface (CI) Module Connector J2 Connector J3 Mechanical coding block (Lower) Figure 1-1 General view and front panel detail (safety covers removed) MHB44IND October 2005 – Issue 2 3
Triguard SC300E SPECIFICATION Model MHB44IND Channels 4 x pulse inputs 4 x analogue outputs Architecture TMR Indicators Health, 3 x On Line Test Point 4 x signal, 1 x common Output range 0 to 22mA Maximum resistive field load 400ohm Resolution 6.25 µA steps Accuracy @ @ 25°C +0.
Triguard SC300E MHB44IND Pulse Input and Analogue Output Module ENVIRONMENTAL SPECIFICATIONS The maximum ambient temperature measured at the hottest point within the Triguard system shall not be greater than 60 degrees centigrade.
Triguard SC300E TECHNICAL DESCRIPTION PHYSICAL The MHB44IND is a 9U high PCB with integral front panel and rear connectors. A plug-in daughterboard carries the common interface circuits. Figure 1-1 shows the general layout, including the location of the connectors, covers and configuration links.
Triguard SC300E MHB44IND Pulse Input and Analogue Output Module MHB44IND October 2005 – Issue 2 7
Triguard SC300E EXTERNAL CONNECTIONS All connections to the MHB44IND are made via DIN 41612 connectors. The upper connector is the system triple I/O bus connector. The middle connector is for the field inputs and outputs. The lower connector is electrically in parallel with the middle connector.
Triguard SC300E MHB44IND Pulse Input and Analogue Output Module THEORY OF OPERATION The module has four isolated 1Hz to 35kHz pulse-input frequency measuring channels, and four 0-22mA current output channels using a common 24V supply via termination card TPH44AIC. The circuits are triplicated except for the final combining of the analogue output stages into a single voted output.
Triguard SC300E Voting operates so that the LFD deviations do not appear on the combined output. If a fault causes health to fail, no further LFD testing is performed.
Triguard SC300E MHB44IND Pulse Input and Analogue Output Module Pulse Inputs The overall period of one or more cycles of the input is measured. Frequency is calculated by dividing the number of cycles by the overall period. The pulse input voltage on each independent path passes via an isolating transformer to an amplifier, which compensates for the frequency characteristics of the transformer and performs automatic level control to cater for the wide range of input amplitude (see Figure 2-2).
Triguard SC300E Analogue outputs Five test-sockets are provided for monitoring the output lines: one common terminal via 2.2k ohm to the +24V field supply, and the other four via 10k ohm to the current-determining resistors on the termination card. These resistors are 250 ohm, so 20mA of loop-current corresponds to 5V across them. The four analogue voltage outputs use 12-bit DACs to produce +0.4V to –6V with respect to field +24V common, applied across resistors on the termination card.
Triguard SC300E MHB44IND Pulse Input and Analogue Output Module Common interface The three discrete control circuits in the Common Interface (A, B, and C) are each responsible for the control of the corresponding one third of the I/O module circuits. Each control circuit comprises a microcontroller with a dedicated watchdog, data buffers and shared RAM. The circuit is powered via the module and permits live insertion of replacement modules.
Triguard SC300E SUPPLEMENTARY INFORMATION Connector J1 is the I/O bus. Field output connectors J2 and J3 are in parallel. The Channel connections are shown in Table 2-1 and Table 2-2. Table 2-1. Pulse input connections to Connector J2 Channel DIN41612 Connector J2 Pulse input Line A Pulse input Line B 1 J2-26a J2-26c 2 J2-28a J2-28c 3 J2-30a J2-30c 4 J2-32a J2-32c Table 2-2.
Triguard SC300E MHB44IND Pulse Input and Analogue Output Module The connectors on J2 that are reserved for future use are shown in Table 2-3. Table 2-3.
Triguard SC300E SERVICING SCOPE System repair is by module replacement. Faulty modules are not repairable in the field. They should be replaced by new modules and returned for repair. CAUTION 1 Before fitting a new module ensure that all the link setting are the same as that on the old module. CAUTION 2 The module contains components that may be electrostatically sensitive, it should be transported and stored in its original packaging material.
Triguard SC300E MHB44IND Pulse Input and Analogue Output Module REMOVAL AND REPLACEMENT CAUTION 4 Failure to take the faulty module off-line before removing it from the chassis could trigger a fault alarm. CAUTION 5 When inserting a module ensure that it is aligned with the markings on the chassis rails, and that it engages with the top and bottom chassis guides. Improper insertion may cause damage to the module and/or chassis connectors.
Triguard SC300E the module into position. Some resistance will be felt as the rear connector pins engage. The module should be fixed in position with the securing screws.
Triguard SC300E MHB44IND Pulse Input and Analogue Output Module 2. Operate the On/Off Line Request switch on the new module. Ascertain that the three On Line LEDs on the new module illuminate for one second, extinguish for one second and then illuminate permanently as the indicators on the old module extinguish. This sequence indicates that the new module has been put on-line and the old module taken off-line.
Triguard SC300E SPARE PARTS Spare parts and technical advice can be obtained from your local area offices.
