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Technical Note TN-151
VRAE Internal view showing location of bias switch position and
sensor positions
INTERCHANGEABILITY
Single Sensor in Different Instruments
• Sensors for the MultiRAE, QRAE, QRAE Plus, and VRAE are
interchangeable among instruments, except for the LEL/VOL
sensor. The MultiRAE and QRAE use the 4R sensor only (p/n
008-1171-002), the VRAE uses either the 4R (p/n 017-1171-
000) or 4R/TC sensor (p/n 017-1172-000), and the QRAE Plus
uses the 3R/TC sensor (p/n 016-1171-000 or 016-1172-000).
The CO
sensor can only be used in the MultiRAE IR.
2
Different Sensors in a Single Instrument
• In the MultiRAE and VRAE, all sensors including the HCN
and PH
sensors (p/n 008-1117 and 19) are interchangeable.
3
Thus, any combination of sensors is possible, except that
the MultiRAE can have only one biased sensor (NO) because
there is only one bias position. In the VRAE, sensors with
a negative current (NO
, Cl
2
position 3, and in the VRAE, sensors with a bias or negative
current cannot be placed in position 4 (see table below).
• The QRAE is limited to the four standard sensors LEL/O
RAE Systems by Honeywell 877-723-2878 raesystems.com
02/08
, and ClO
) cannot be placed in
2
2
/CO/H
2
Sensors
Gas
Bias
CO
Off
H
S
Off
2
SO
Off
2
NO
ON
NO
Off
2
Cl
Off
2
ClO
Off
2
NH
Off
3
HCN
Off
PH
Off
3
EXTENDED CALIBRATION TIMES
Slowly responding sensors listed in the table below may require pre-
exposure of the sensor to the gas immediately before initiating the
calibration sequence. Some firmware versions use a fixed 60-second
calibration time; some newer versions automatically apply the full
calibration time. After completing the zero calibration, expose the
unit to the gas for the pre-exposure time listed below if a 60-second
countdown time is programmed in the unit. In many cases when a
pre-exposure is performed, the unit gives a warning message "No
gas..." when calibration is initiated. Simply push the [Y/-] button to
bypass the warning and proceed wit the calibration.
Response Time
Sensor
HCN
CLO
, NH
,
2
3
COCl
2
CL
, PH
2
3
S.
2
CO, H
S, SO
,
2
2
NO, NO
, LEL,
2
VOL
PGM-7800
Tox1,2
Tox1,2,3
Tox3 Loc.
Loc.
Loc.
OK
OK
OK
OK
OK
OK
OK
OK
OK
OK bias
OK bias
OK
on
on
Not
OK
OK
allowed
Not
OK
OK
allowed
Not
OK
OK
allowed
OK bias
OK bias
OK bias
off
off
off
OK
OK
OK
OK
OK
OK
Total
Calibration
t
(sec)
90
Time (sec)
200
230
150
150
60
120
≤40
60
PGM-7840
Tox4 Loc.
OK
OK
OK
Not
allowed
Not
allowed
Not
allowed
Not
allowed
OK bias
off
OK
OK
Pre-exposure
Time for 1-min
Calibration
Time
170
90
60
0
3
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