1535 Relative Humidity Transmitter - Novatech Controls

!1.12 AUTO CALIBRATION CHECKING–PROBEAs stated in Section 1.3, on-line automatic gas calibration is not normally required. Where it is required however, theprobe can be checked for accuracy in-situ and on-line. Solenoid valves can admit up to two calibrated gas mixturesinto the probe via the calibration port, under microprocessor control, on a timed basis. For details on installationrefer Section 2.10. For details on setting up this facility refer to set-up steps 11 to 23 Section 4.5.During probe auto calibration checking, the transmitter output will freeze and remain frozen for a further adjustableperiod, allowing the probe time to recover and continue reading the drier oxygen level.Calibration gases may be manually admitted by pressing the ‘CAL’ buttons on the keyboard while in ‘RUN’ mode.The transmitter output is frozen during the pressing of these buttons and immediately becomes active when thebutton is released.1.13 AUTO PURGEIn oil and coal fired plants, or in dryers with high dust loadings, it is possible for the probe sensing filter to becomeblocked. An automatic purge cycle can be set up so that a blast of air, maximum 100 kPa, will automatically backflushthe probe filter on a timed basis. Refer to set-up steps 11 to 15 Section 4.5.A purge flow switch senses that there is sufficient flow to clear the filter during the purge cycle otherwise a ‘FILTERBLOCKED’ alarm will occur.The probe can be manually purged from the keyboard while in ‘RUN’ mode. The transmitter output is not frozenduring or after the pressing of this button.1.14 RS 485 –232C PORTSThe serial port is for connecting a printer, a data logger, or any computer with an RS485 –232-C port.It can be used to monitor the transmitter and process by logging the values of functions selected in step 29 of the setupmenu.The log period may be selected in step 30 for 1–2000 minutes, and the baud rate may be set up in step 31.Alarms, including the time they occurred, will be transmitted to the printer and computer whenever they are firstinitiated, accepted and cleared.NOVATECH HUMIDITY TRANSMITTER Page 15