Analytical Industries GPR-28 Oxygen Analyzer - Manual (Page 19)

Advanced Instruments Inc.
19
Alarms
The analyzer is equipped with two user adjustable alarms located on the interior panel attached to the front door. When
activated the alarms trigger SPDT Form C, normally closed, non-latching relays @ 5A, 30VDC or 240VAC resistive. The alarms
are fully adjustable by the two potentiometers accessible from the auxiliary panel on the inside of the door with a small bladed
screwdriver. Optionally, alarm control actuators can be mounted externally as illustrated in the Mounting the Analyzer section
above.
Note: Fail safe alarm configuration - connect positive lead to NO and negative to the C, common or neutral. To connect to an
active relay, connect the live cable to the common terminal C and the secondary cable to the normally open NO terminal. To
break the connection upon relay activation, connect the secondary cable to the normally closed NC terminal.
Power Fail Alarm
A dry contact rated at 30VDC @ 1A is provided as a power failure alarm. The contact is normally closed but opens when the
power to the analyzer is switched off or interrupted. Connect the lead wires from the external recording device to the male
phone plug supplied with analyzer.
Sensor Fail Alarm
A 5V output with negative ground is provided when the sensor is operational. The output is 0V when the sensor fails and its
output goes to zero. Note: Adjusting the ZERO OFFSET to .000 activates the Sensor Failure Alarm characterized by a
momentary spike in the trend analysis. To avoid the spike set the ZERO OFFSET to .001
Caution: The sensor failure alarm becomes active when the display indicates ‘000’ on any range of the analyzer. To verify the
‘sensor failure’ condition, advance the range switch to the lowest (most sensitive) range available. If the display continues to
indicate ‘000’ or a negative number, replace the sensor.
Range ID Output
A voltage output corresponding to each range is provided. The output of the highest range (normally CAL) is 5V and the
remaining three ranges 4V, 3V and 2V for the low range.
Signal Outputs
The analyzer provides an isolated 4-20mA signal output and a 0-1V full scale signal output for external recording devices. The
integral IC on the main PCB converts the 0-1V signal with negative ground to a 4-20mA fully isolated signal. A finer adjustment
of the zero offset of the 4-20mA converter can be provided by a potentiometer, R99, mounted on the main PCB Assembly.
Consult factory for instructions. Caution:
The integral 4-20mA converter is internally powered and does not require external
power. DO NOT supply any voltage to either of the two terminals of the 4-20mA converter.
Temperature Controller
If the optional the temperature controlled heater system is installed, access it by opening the front door. This unit is a PID
controller that operates between 0-99
°F. The controller is programmed to maintain the temperature at 75-85°F. Caution: Do
not change this setting. A higher temperature setting may drastically reduce sensor life and possibly cause damage to the
electronic circuitry of both the controller and the analyzer.
When power is applied to the temperature controller, the controller tunes itself to eliminate and/or minimize the over/under
shoot of temperature from the setpoint. It is recommended that at initial start-up, when replacing the oxygen sensor or when
trouble shooting; turn the power to the heater off or set the temperature set point at 60
°F to turn the heater off to prevent
overheating the analyzer. Caution: Keep the analyzer front door closed and securely fastened when the temperature controller
is ON.
Heater Runaway Protection
As part of the optional temperature controlled heater system, the analyzer is protected in the event the temperature controller
should fail and thereby allowing the heater to runaway damaging the interior of the analysis unit. The runaway protection is
provided by a J2 type device positioned between the temperature controller and the heater. This device cuts of power to the
heater if the temperature inside the analysis unit exceeds 70
°C. Correct the problem and reset the runaway protector device by
exposing it to 0 °C for a few minutes (a refrigerator freezer will do).
Additional electrical diagrams are provided for reference purposes in Appendix I.