Psychrometer
a current of air. When the power supply is connected and the integrated fan
starts operating, the moistened temperature sensor will, depending on air tem-
perature and humidity, cool down by a measurable amount. Based on this psy-
chrometric temperature difference the water vapor’s partial pressure e´ and
thus all the variables associated with atmospheric humidity can be calculated.
5.3 Measuring instrument
The reference measuring instrument ALMEMO
®
1036-2 belongs to the new X6
series of high precision measuring instruments featuring very high resolution
and linearity. The ALMEMO
®
1036-2 provides 2 galvanically isolated measuring
inputs for Pt100 sensors with a measuring range from -200 to 400/560°C and a
resolution of 0.001K. Since the temperature values can be calculated precisely
thanks to appropriate formulas, there will be no linearization errors concerning
the resolution. The measurement accuracy of up to 760,000 digits is signifi-
cantly higher than the usual 16bit numbers (65000) for other ALMEMO
®
V6 de-
vices. Due to this high measurement accuracy, the standard functions limit val-
ues, measured value correction, scaling or analog outputs cannot be sup-
ported. Alternatively, the possibility for multi-point adjustment of 24bit basic
value interpolation or of the modification of coefficients is offered. Thanks to
that, the ALMEMO
®
1036-2 is perfectly suited as a precision reference instru-
ment for temperatures as well as – in combination with the psychrometer – for
all humidity variables.
The Pt100 psychrometer can be used to measure very accurately both dry
temperature and humid temperature and thus calculate all the usual humidity
variables on the basis of formulae as per Dr. Sonntag and the enhancement
factor as per W. Bögel (correction factor fw(t,p) for real mixed gas systems).
These calculations must take account of atmospheric pressure; for this pur-
pose the device incorporates as standard an atmospheric pressure sensor.
The measuring range and accuracy of this device are thus much greater than
with previous systems. The atmospheric pressure measured can also be used
as an additional climate variable.
Device 1036-2 can also have two digital D6 humidity sensors connected,
namely NTC psychrometer FNAD36-3, and capacitive humidity sensor
FHAD46-RS (for up to maximum 200 °C). Both use exactly the same calcula-
tion principles and internal atmospheric pressure compensation as the Pt100
psychrometer.
To facilitate operation the device incorporates an illuminated LCD graphics dis-
play and a keypad with softkeys and cursor block. The device incorporates
three output sockets for connecting interface cables, a memory connector, or a
mains unit.
ALMEMO
®
1036
9
