Minco
Tel: 763. 571.3121 • Fax: 763. 571.0927 • www.minco.com
2
Description
Model AH440 is humidity / temperature assembly consisting of separate 2-wire temperature compensated
humidity and temperature transmitters, as well as a rugged sensing probe. The assembly utilizes a Honeywell
HIH series monolithic IC humidity sensor, which provides excellent stability and chemical resistivity. The
humidity transmitter converts the humidity sensor’s signal into a 4 to 20 mA DC current, which changes
proportionally from 4 mA at 0% RH to 20 mA at 100% RH. The leads that supply power also carry the current
signal. The additional temperature transmitter provides a second 4 to 20 mA DC output where the current
changes from 4 mA at the lowest temperature of the range, to 20 mA at the top of the temperature range.
The range of the temperature transmitter can be re-scaled via dip-switches. These transmitters have non-
interacting, field adjustable zero and span pots and are available in duct mount, wall mount, outside air (OSA),
and space mount configurations.
Specifications
Output(s):
Humidity: 4 to 20 mA DC = 0% to 100% RH.
Temperature: 4 to 20 mA DC over specified range.
Sensing Element:
Humidity: Capacitive monolithic IC.
Temperature: 1000 ohm platinum; 2 lead RTD.
Ambient Temperature:
Operating:
Room: -10 to 150°F (-23 to 65°C), non-condensing.
Duct/Wall/OSA: -10 to 185°F (-23 to 85°C), non-condensing.
Storage:
Room: -58 to 150°F (-50 to 65°C), non-condensing.
Duct/Wall/OSA: -58 to 185°F (-50 to 85°C), non-condensing.
Supply voltage:
9.5 to 35 VDC, non-polarized.
Voltage effect:
.001% of span/volt from 9.5 to 35 VDC.
Loop resistance:
The maximum allowable resistance of the signal-carrying loop, including
extension wires and load resistors, is given by this formula: R
loopmax
= (V
supply
-
9.5)/0.02 AMPS. For example, if supply voltage is
24 VDC, the loop resistance must be less than 725
Ω
.
Accuracy:
Includes temperature, linearity, hysteresis, repeatability, and voltage effects.
Humidity:
±1% from 10% to 80% RH @ 25 to 35°C or ±2% from 0% to 90% RH @ 25°C.
(±3% from 0% to 90% RH @ 15 to 50°C).
(±5% from 0% to 90% RH @ 0 to 82°C).
Temperature:
± 0.75% of span for 32 to 122°F ambient
± 1.5% of span for -13 to 185°F ambient
Adjustments:
Zero and Span field adjustments, non-interacting.
Time Constant:
50 seconds in slow moving air.
Connections:
Screw terminals (22-14 AWG wire).
Weight:
1.77 lb (0.81 kg).
Minimum output current:
3.5 mA.
Maximum output current:
23 mA.