Category: Industry trends

This article introduces the strategies for troubleshooting and repairing problems with the Bentley 3500 monitoring system and eddy current sensor system.

When any part of an electronic device malfunctions, the main goal is to identify and repair the fault so that the device can resume operation as soon as possible. If this device is a part of the mechanical monitoring system, this goal will become even more important.

As shown in Figure 1, this diagnostic step divides the 3500 monitoring system into three parts:

I. On-site wiring and preamplifier

Ii. Extension cables and probes

Iii. Framework

The inspection steps are as follows:

Measure the sensor supply voltage (-VT) between the PWR and COM terminals of the I/O module on the monitor, and its value should be -23.7±0.5VDC.

If -VT is outside the allowable range, the problem occurs in the monitor or I/O module. This is because the -VT voltage regulator is present in both of these components. Remove the PWR terminal signal line, replace the monitor or I/O module with a compatible component, and measure the voltage between PWR and COM to diagnose the faulty component.

If -VT is within the allowable range and the monitor or I/O module is functioning properly, proceed to the next monitoring step.

2. Measure the voltage between the terminals on the preamplifier. The power supply voltage -VT of the preamplifier should be -23.7±0.5VDC.

If -VT is outside the allowable range and there is a fault in the on-site signal line, disconnect the VT line of the eddy current sensor and measure the terminal voltage -VT. If -VT is still outside the allowable range, there is a problem with the on-site wiring. If -VT is within the allowable range, replace the eddy current sensor with a compatible spare part.

If -VT is within the allowable range, proceed to the next monitoring step.

3. Disconnect the signal line at the OUT terminal and measure the DC gap voltage between COM and OUT. This voltage value should be within the OK voltage range of the eddy current sensor.

If the OK voltage exceeds the range, check the extension cord of the sensor, then disconnect the signal line on the SIG/A terminal of the I/O module and measure the DC gap voltage between COM and SIG/A. The voltage should be within the OK range of the eddy current sensor. If the OK voltage is out of range, replace the on-site cable. If the OK voltage is within the range, reconnect the SIG/A terminal signal line and replace the monitor with a compatible device.

If the OK voltage is within the range, reconnect the signal line at the OUT terminal and proceed to the next monitoring step.

4. Test probes and extension cables

Reconnect the field signal lines on the OUT terminal of the preamplifier, remove the coaxial extension cable connector on the preamplifier, and confirm that the coaxial socket on the preamplifier and the plug on the extension cable are clean. Measure the resistance between the outer conductor and the inner conductor of the extension cable. The normal resistance value should be between 7 and 11 ohms, depending on the electrical length of the sensor system.

If the resistance exceeds the limit, disconnect the coaxial plug between the probe and the extension cable, and ensure that the coaxial socket on the extension cable and the coaxial plug on the probe are clean. Measure the resistance between the outer conductor and the inner conductor of the probe. If the resistance exceeds the limit, replace the probe with a compatible spare part. If the resistance does not exceed the limit, replace the extension cable with a compatible spare part.

If the resistance is within the normal range, there is no fault with the probe and the extension cable.

Input/output module

The input and output module, also known as the control module, can output signals or provide a switch signal when there are control requirements, causing the controlled equipment to act. At the same time, it can receive feedback signals from the equipment to report to the host. It is an important component of the fire alarm interlocking system. All input and output modules on the market can provide a pair of passive normally open/normally closed contacts. To control the controlled equipment, some manufacturers’ modules can be set to active output through parameter Settings (such as Gulf GST-LD-8301). Correspondingly, there are also dual input/output modules, multi-input/output modules, etc.

Function and role

When a fire alarm is triggered, the alarm controller activates the external control devices that need to be linked through the output module, such as smoke exhaust valves, supply air valves, fireproof rolling shutters, fans, alarm bells, etc., and can respond to the actions of the devices.
The output module is connected to the loop bus of the controller and can be installed near the controlled device or in the floor terminal module box. It adopts electronic coding and can be encoded on the spot. The output control logic of the output module can be programmed according to the engineering situation. When the controller receives the alarm signal from the detector, according to the pre-programmed program, the controller transmits the interlocking control signal to the output module through the bus, and the output module starts the fire protection equipment that needs to be interlocked. After the device operates, it will receive a signal response.

Product Description

Features
The GST-LD-8301 input/output module is a bus-based control interface that can be used to control double-action equipment such as two-step fireproof rolling shutters, water pumps, and smoke exhaust fans. It is mainly used for the position control of fireproof rolling shutter doors, capable of controlling them from the top position to the middle position, as well as from the middle position to the bottom position. At the same time, it can also confirm which position the fireproof rolling shutter door is in, top, middle or bottom. This module can also be used as two independent GST-LD-8301 input/output modules.
The GST-LD-8303 input/output module has two consecutive encoding addresses with a maximum encoding of 242. It can receive commands for two different actions from the controller and has the functions of two different control outputs and confirming two different input response signals. The input signal required for this module is a normally open switch signal. Once the switch signal is activated, GST-LD-8303 sends this switch signal to the controller through the interlocking bus. The interlocking controller generates an alarm and displays the address number of the activated device. When the module itself malfunctions, the controller will also generate an alarm and display the module number. This module features two pairs of normally open and normally closed contacts as well as two sets of active outputs. The input and output have wire detection functions.
The encoding method of the GST-LD-8303 module is electronic encoding. After one encoding address is assigned, another encoding address is automatically generated as: assigned address +1. This encoding method is simple and fast. During on-site encoding, the GST-BMQ-2 electronic encoder produced by Gulf Company is used.
Main technical indicators
(1) Working voltage
Bus voltage: 24V bus
Power supply voltage: DC24V
(2) Monitoring current:
The bus current is ≤1mA
The power supply current is ≤6mA
(3) Operating current: Bus current ≤4mA
The power supply current is ≤35mA
(4) Wire system: It is connected to the controller via a non-polar signal two-bus and to the DC24V power supply via a non-polar power supply two-bus
(5) Output capacity: DC24V/1A (The sum of the maximum capacities of the two output groups is DC24V/1A)
(6) Output control mode: Pulse, level (relay normally open/normally closed passive contact output, relay engagement time is 10 seconds when pulse starts)
(7) Factory Settings: Two normally open inspection lines
(8) Usage environment:
Temperature: -10℃ to +55℃
Relative humidity ≤95%, no condensation
(9) Enclosure protection grade: IP30
(10) Dimensions:
110mm×86mm×43mm (with bottom shell)

Wiring method

If the module input terminal is set to the “normally open test line” state input, a 4.7kΩ terminal resistor must be connected in parallel at the end of the module input line (far from the module end). If the input terminal of the module is set to the “normally closed test line” state, a 4.7kΩ terminal resistor must be connected in series at the end of the input line of the module (far from the module end). When the module is an active output, a 4.7kΩ terminal resistor should be connected in parallel at the active output terminal, and an IN4007 diode should be connected in series.