Normal Mode
The sensor will begin reading the CO
2
level (and temperature if it is installed), output the correct analog signal and display the values
on the LCD. If the relay is installed, the measurements will be compared to the setpoint and appropriate action taken. The keypad is
monitored and if the <MENU> key is pressed the device will enter the Setup Menu. The Setup Menu can be accessed to configure
the device for required operation.
Relay Mode
The optional relay can be used as an alarm signal to indicate that a setpoint has been exceeded. For the basic CO
2
product, the relay
may be configured via the Setup Menu as a high or low alarm and the setpoint value, hysteresis and on-delay time may be set. The
relay will activate and close the contacts if the CO
2
measurement goes above the setpoint (for a high alarm) or below the setpoint (for
a low alarm). If required, this action can be delayed by a time period (relay delay time) to prevent false alarms. After the relay is
activated, the measurement must fall below the setpoint - hysteresis value (for a high alarm) or go above the setpoint + hysteresis
value (for a low alarm) to deactivate the relay and open the contacts. The high/low assignment, setpoint, delay time and hysteresis
values may all be programmed via the Setup Menu as required.
If the optional temperature sensor is installed, the relay operation may be assigned to operate as a temperature high or low alarm
instead of a CO
2
alarm. All the same relay parameters may be configured to set up the alarm as required.
User Menu
The device has several parameters that can be configured locally via the Setup menu using the keypad and LCD. Any changes made
are saved in non-volatile memory and are restored in case of a power loss. The menu can be accessed at any time after the start-up
mode and if there is 5 minutes of inactivity the menu will close and normal operation will continue.
To enter the menu, press and release the <MENU> key. This will enter the Setup Menu step 1, pressing the <MENU> key a second
time saves the setting and advances to step 2. Each press of the <MENU> key saves the current setting and advances the menu
item. The <UP> and <DOWN> keys are used to make changes to program variables by scrolling through the available options. The
first column below shows what will be displayed on the LCD, including the default value.
Press and release to enter the SETUP menu
2000 ppm
2
Span value controls the analog output scaling. CO
2
span can be changed from 1000 to
10,000 ppm in 500 ppm increments using <UP> or <DOWN>. If CO
2
Span = 2000 ppm, then the
output signal is scaled 0-2000 ppm = 4-20 mA. Factory default is 2000 ppm.
Press to advance to next menu item.
ON
The Self-Cal feature <MENU> when enabled requires the sensor to be exposed to fresh air for at
least one hour every twenty-four hours. When first installed the sensor requires a minimum of seven
days of operation with fresh air exposer daily to allow the algorithm to adjust for self-calibration.
Default for device is having this feature disabled enabled “ON". If disabling this feature a manual
calibration should be performed to ensure accuracy of the device.
Press to advance to next menu item.
0 m
The Altitude value allows CO
2
compensation for local atmospheric pressure and altitude and ensures
the highest CO
2
accuracy. Altitude can be changed from 0 to 2550 meters in 50 meter steps using
<UP> or <DOWN>. It will take a few moments to change the setting, then the menu will advance to
the next step. Factory default is 0 m (sea level).
Press to advance to next menu item.
0-5 Vdc
The V Output value controls the analog output voltage span if the PCB switch is set to VOLT. V Output
can be set to either 0-5 Vdc or 0-10 Vdc using <UP> or <DOWN>. This setting has no effect if the
PCB switch is set to mA. Factory default is 0-5 Vdc.
Press to advance to next menu item.
Direct
The Output value controls the analog output signal direction. Use <UP> or<DOWN> to change the
setting from Direct (4-20 mA, 0-5 Vdc or 0-10 Vdc) to Reverse (20-4 mA, 5-0 Vdc or 10-0 Vdc) if
reverse action is required. Factory default is Direct.
Press to advance to next menu item.
Test OFF
The Output Test value controls the analog output signal for testing purposes. Use <UP> or <DOWN>
to toggle the output signal to OFF (normal operation), MIN (minimum output) or MAX (maximum
output). The actual output signal will depend on the PCB switch position (mA or VOLT) and the V
Output setting (for voltage operation). Press <MENU> to set it back to OFF and advance. Factory
default is OFF.
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