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HA20 2-Channel Controller
2.2.6 Calibrate Input Menu
Calibration is the most important function for ensuring correct operation
of HA20s equipped with sensor inputs. The CAL MODE (flow chart
shown in
Figure
2-7) is designed to make calibration quick, easy and
error free. A successful ZERO and SPAN calibration requires only five
keystrokes. Optional 4-20mA outputs (if equipped) transmit 1.5mA
during CAL MODE and 4mA during the subsequent CAL PURGE
delay to prevent external alarms during calibration. Local HA20 alarm
relays are inhibited during CAL MODE. Unintentional calibrations
may be reset using the Set UNITY menu item. Set UNITY resets
CAL OFFSET to 0 & CAL GAIN to 1 which is useful for returning the
calibration to a known starting place. Sensor aging may be monitored
by recording zero and span readings at Unity Gain when the sensor
is new, and again later when degradation may have occurred. CAL
MODE automatically exits if no keystroke is detected after 5 minutes.
Follow these sensor calibration guidelines:
• Calibration accuracy is only as good as the calibration standard
accuracy. Honeywell Analytics recommends calibration
standards with NIST (National Institute of Standards and
Technology) traceable accuracy to increase the validity of the
calibration.
• Do not use a gas cylinder beyond its expiration date.
• Calibrate a new sensor before use.
• Allow the sensor to stabilize before starting calibration. (Consult
the appropriate sensor manual for warm-up times.)
• Calibrate on a regular schedule. (Consult the appropriate sensor
manual for calibration intervals or depending on use and sensor
exposure to poisons and contaminants.)
• Calibrate only in a clean atmosphere free of background gas.
HA20 Technical Manual
Use the following step-by-step procedure to perform ZERO and SPAN
calibrations.
1. To enter the CAL MODE from any data display, press the dual
purpose down arrow/CAL key and press the Edit key within 5
seconds then select channel.
2. Using the Cal-Cup and following the instructions on the screen,
apply a clean ZERO gas or be sure there is no background
target gas in the monitored area. After the reading is stable,
(approximately 1 minute) press the Edit key to perform a ZERO
calibration.
3. If the ZERO calibration is successful, CAL MODE automatically
proceeds to the SPAN check.
4. Apply the correct SPAN calibration standard. After the reading
is stable, press the Edit key to perform a SPAN calibration.
WARNING
The SPAN gas used must match the value specified since this is what
the HA20 will indicate after a successful SPAN calibration. The Span
Gas value may be edited if it becomes necessary to apply a different
gas concentration (see Figure 2.6 [Span Gas] in
5. If the SPAN calibration is successful, the display flashes
"REMOVE CAL GAS" and starts the CAL PURGE delay.
6. CAL MODE will be complete after the end of the CAL PURGE
delay.
2-6
Section
2.2.5).
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