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1.14 RS 485 NETWORK (MODBUS™) AND RS 232C PORT
The serial port has two functions. -
•
It can be configured to connect up to 31 analysers together on a MODBUS™ RS485 network.
Each individual analyser can be interrogated by a computer or PLC. The values of oxygen, sensor EMF, sensor
temperature, sensor impedance for both oxygen sensors (if two sensors are being used on one analyser) can be read over
the network, as well as calculated values such as water vapour %, dew point etc.
The alarm status can also be checked over the network.
For the connection details, see Section 2.15 and Appendix 3.
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It can be used to log the analyser readings by connecting the analyser to a printer, a data logger, or any
computer using an RS232-C port.
To configure the data logging capabilities of the device, use set-up step 58 to select the items to be logged. The log
period may be selected in set-up step 59, and the baud rate may be set in set-up step 60. Alarms, including the time they
occurred are transmitted to the printer and computer whenever they are first initiated, accepted and cleared. The
protocol for the serial port is eight data bits, one stop bit, no parity.
1.15 DRYER OR OVEN TEMPERATURE (AUX) THERMOCOUPLE
A type K dryer or oven thermocouple should be installed and connected only when relative humidity display is
required. This is an unlikely requirement for high temperature drying or baking processes because the relative humidity
is very low. Greater resolution is achieved with % water vapour, moisture or dewpoint measurement.
The auxiliary thermocouple input is not available when an RGS-01 is being used in direct fired systems.
1.16 MODES WITH SWITCHING CAL 2 SOLENOID
When operating the device in dryer heater type Mode 5Auto and Mode 6 Timed & Auto, terminals 45 & 46 (cal 2 sol)
serve as an output to control an external solenoid critical to these modes of operation. In Mode 5 Auto, this solenoid
relay is energised when the device is sampling from the RGS-01 sensor and could be used as an indicator/solenoid
controller to enable gas flow to the sensor.
In Mode 6 theis relay controls a solenoid which switches reference air / dry process gas to the reference input on the
sensor. The solenoid should be configured so that when it is energised the probe reference should be plumbed to the
dry process gas, and when de-energised it should be reference air.
1.17 WATCHDOG TIMER
The watchdog timer is started if the microprocessor fails to pulse it within any one second period, (i.e. fails to run its
normal program). The microprocessor will then be reset up to three times until normal operation is resumed. Reset
cycles are displayed by the RESET light on the internal keyboard. A steady 'ON' light indicates normal operation. If
the program has not resumed normal operation after three attempts to reset, the common alarm relay will be activated.
The reset function will continue repeatedly after the alarm. If a successful reset is achieved, the alarm will be cancelled
and the analyser will continue to run normally.
1.18 BACK-UP BATTERY
The analyser's RAM and real-time clock are backed up by a lithium battery in the event of power failure.
12
August 2009
1635 Water Vapour Analyser
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