Calibration Procedure - Honeywell 705 Operating Instructions Manual

MAN0364.P65 Issue 03, Mar 01
00705M5003

5.4 CALIBRATION PROCEDURE

Notes: 1. Ensure that the sensor is not pressurised during
(1)
(2)
(3)
(4)
(5)
(6)
5. CALIBRATION
calibration by blockage of the exhaust (outlet of
the Flow Housing).
2. This procedure will produce an upscale output
signal which may activate alarms if fitted. Refer to
the Warnings in Section 2 Installation before
proceeding.
Allow a minimum warm-up period of 1 hour after
applying power before carrying out this procedure.
Insert the Digital Multimeter (DMM), set to read current,
in series with the 4 - 20mA line.
Ensure that the sensor is in a gas-free atmosphere
then, if necessary, adjust the ZERO control for 4mA
on the DMM.
Gas the sensor as instructed in Section 6 'Gassing the
Sensor'. After 3 minutes, set the SPAN control to
obtain a 20mA indication on the DMM for 50ppm CO.
If procedures (3) and (4) cannot be achieved, adjust
the OFFSET control as follows:
a. Connect the DMM (set to read mV) between
TP2 and TP3 on pcb. (see Figure 7).
b. Adjust the ZERO control to obtain a reading of
0.000V ± 1mV on the DMM.
c. Disconnect the DMM.
d. Adjust the OFFSET control to obtain an output
(at the terminals) of 4mA.
e. Repeat steps (3) and (4). Remove the gas
adaptor and allow sufficient time for the test gas
to escape.
Turn off the test gas and check the DMM indicates
4mA. If not, adjust the ZERO control for a DMM reading
of 4mA.
20
705 Sensor CO