Kahn S4000 Integrale, Installation, Operation And Maintenance Manual

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KAHN INSTRUMENTS, INC.
885 Wells Road, Wethersfield, CT 06109
Tel: 860-529-8643; Fax: 860-529-1895
E-mail: info@kahn.com
www.kahn.com
4. OPERATION
4.1 General
Operation of the Series 4000
Integrale
Precision Hygrometer is very simple as long as
necessary precautions are taken to provide an accurate sample of the gas to be
measured. Statistical information indicates that the vast majority of failures are caused
either by incorrect sampling methods, sampling positions or inadequate protection
against dangerous substances.
4.2 Sampling Hints
The Series 4000 Precision Hygrometer sensor is designed to operate in a flowing gas
stream. It is provided with a sampling chamber, which enables a small sample of gas to
be passed over a Peltier cooled, plated copper mirror. The sample gas is bled off to
atmosphere through the Monitor Unit front panel coupling marked "GAS OUT".
Although the correct operation of the sensor is not flow-rate dependent it is important to
ensure that the flow velocity through the sample line, connecting the sample source to
the Monitor Unit, is high enough to avoid long time lags in response to changes in
humidity at the sample source. We therefore recommend a flow rate of between 50 and
200 cm
3
/min. (0.05 to 0.2 l/min.) be set. The ideal figure is 150 cm
3
/min (0.15 l/min). A
flowmeter is provided on the front panel of the Monitor Unit.
Flow regulation is not provided within the Monitor Unit. If gas flow must be regulated, add
a precision needle valve or similar device at a suitable location in the sample gas stream
before the "GAS IN" coupling on the unit. Take care not to introduce errors into the
system by using inferior quality valves or making poor connections. Avoid pressure
gradients in the system by excess flow restriction after the sensor. If the test gas has a
very high flow rate then a by-pass arrangement is preferable to a flow restriction after the
sensor.
The general rules to be adhered to when arranging a sampling system are as follows:
a) Ensure the sample is representative of the gas under test.
The sample point should be as close to the critical measurement point as
possible. For example, in a glove box application connect the sensor at the
exit of the glove box not at the gas entry point.
b)
Minimize dead space in sample lines.