Det-Tronics NTMOS IP66/IP67 H2S Gas Detector - Manual (Page 9)

2.1 95-8670 7
IMPORTANT CALIBRATION NOTES
• Proper calibration requires the use of either
D et‑Tronics’ NTMOS calibration kit with
humidification tube and bottled H
2
S in air
(p/n 010272‑001), or the ampoule calibration
kit (p/n 007098‑005).
• When calibrating with bottled H
2
S in air, the
humidification tube must be utilized, or inaccurate
readings will occur.
• WARNING: Using a gas mixture other than
50% span of H
2
S in air will produce inaccurate
calibration results, possibly resulting in a
dangerous condition if the detector under‑reports
the level of H
2
S. Do not use bottled H
2
S with
nitrogen.
• Prevent all contact of any oil based material from
the humidification tube.
If background H
2
S gas is present, it may be necessary
to purge the detector with clean air to ensure that an
accurate zero or “clean air” condition is present prior to
initiating calibration.
CALIBRATION PROCEDURE
The NTMOS Detector requires zero and span
calibration, achievable with the NTMOS calibration kit
or the ampoule calibration kit. It is highly recommended
that the FlexVu UD10 Display Unit, GDTB Termination
Box, Model U9500B Transmitter, or Model R8471B
Controller be utilized with the NTMOS Detector to enable
non-intrusive field calibration. When using the UD10,
U9500B, or R8471B for calibration, refer to the related
manual for specific calibration instructions.
Calibrating a Stand-Alone NTMOS Detector
1. A dc current meter capable of measuring 4-20 mA
must be connected to the current loop output. This
can be accomplished by connecting a dc ammeter
in series with the load or by connecting a digital
dc voltmeter across a known load resistance and
calculating the current flow using the formula:
current (I) = voltage/load resistance.
2. If the detector is powered-up after a shutdown,
it must be allowed to warm-up for a period of 16
hours prior to calibration. (Before calibrating a new
detector, allow a 24 hour warm-up period after initial
power-up).
3. Initiate calibration by activating the calibration line.
4. The current output goes to 2.2 mA while the detector
automatically calibrates the zero output.
5. When the current output goes to 2.0 mA, apply 50%
span of H
2
S gas in air to the detector using the
humidification tube kit, or the ampoule calibration
kit. When using the humidification tube it must be
attached to the detector via a cal cup before applying
gas, and ensure that the flow rate is set to 0.5 liters/
min.
6. Upon successful calibration, the current output will
go to 1.8 mA. Remove the calibration gas. The
output will go to 4 mA. Reference Table 2 for the
calibration sequence.
NOTE
If the current output reads 1.6 mA, the calibration
has failed. Check the calibration gas expiration
date, verify that the calibration gas used is H
2
S
in air, or replace the detector and repeat the
calibration. Be certain that the humidification tube
is used during calibration.
Current Output Detector Action Operator Action
Actuate Cal Line
2.2 mA Zero Cal None
1.6 mA Cal Failed Repeat Calibration
2.0 mA Span Cal Apply Cal gas
1.8 mA Cal Complete Remove Gas
4.0 mA Normal Operation
Table 2—NTMOS Detector Calibration Sequence