Ambient Air quality Monitoring Guidlines. - Maharashtra Pollution ...

No. of Poles
(See Circuit
Diagram)
Cross Section of Core Total Diameter
5 0.25…0.38 mm 2 5.2…5.7 mm
10 0.25…0.38 mm 2 7.7…8.2 mm
(v) Maintenance - In the interest of measuring accuracy, it is advisable to check out
the display and to regenerate the hairs in saturated moist air from time to time.
However, if there are only minor changes in humidity, it is sufficient to re-set the
hairs, regeneration isn't necessary. Hygro-transmitters used in moist air with
over 80% relative humidity do not require regeneration. Transmitters which are
exposed to dry air frequently or over long periods of time must be regenerated
more frequently. Hygro-transmitters which have not been regenerated will, in the
course of time, start to indicate values which are about 5-8% too high. This
degeneration can be reserved by exposing the hygro-transmitter to saturated
moist air.
The easiest way to do this is to wrap the immersion stem of the hygro-transmitter
for about 60 minutes in a damp cloth which has been dipped in lukewarm water.
Make sure that the stem is completely enclosed in the cloth and that no air can
get at it.
Normally, the indicator will settle at 94-96% relative humidity. If, there are
significant deviations from this value, then correct this by means of the setting
screw marked in red at the lower end of the stem. The hygro-transmitter which is
correct at 95% relative humidity will also be correct and in accordance with the
adjustment at all other humidities, provided that the characteristic hygrometric
features of the hair have not changed as a result of damaging influences (heat,
aggressive vapors, mechanical tearing etc.).
If, the hygro-transmitter is used with a wind protector, then it will be necessary to
check this regularly. If, it is dirty, remove it from the instrument and clean it.
3.1.2 Temperature
(i) Hygro-thermo-transmitter - Hygro-thermo-transmitters resemble the hygrotransmitters
just described. They are equipped with an additional hard-glass
resistor Pt 100 in the immersion stem. This resistor is suitable for use when
long-range measurements of temperature with high resolutions are required.
The change in resistance in the platinum coiling as a result of changes in
temperature is a measure of temperature. The relationship between resistance
and temperature has been set down in DIN 43760. The term Pt 100 is the basic
value of 100 ohm at 0 o C.
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