Intrinsically Safe Humidity Assembly

Operating Temperature: Transmitter:-40 to 17 6 °F (-40 to 80°C), non-condensing.-4 to 17 6 °F (-20 to 80°C), non-condensing, model AH75.Sensor:-40 to 17 6 °F (-40 to 80°C), Storage Temperature: -58 to 185°F (-50 to 85°C), non-condensing. Supply voltage: 9.5 to 28 VDC . Voltage effect: ±0.001% of span/volt from 9.5 to 28 VDC. Loop resistance: The maximum allowable resistance of the sig-nal-carrying loop, including extension wires and load resistors, is given by this formula: R

Overview

Models AH74 and AH75 are 2-wire temperature compensatedhumidity transmitters that are FM and CFM approved as intrinsically safe for use in hazardous locations. Both models are available with an optional temperature transmitter output. AH75 incorporates a digital display for remote indication of relative humidity and temperature. The transmitters utilize a thin film capacitive humidity sensorwhich provides outstanding sensitivity and chemical robust- ness. The 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 optional temperature loop produces 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 leads that supply power also carry the current signal.•Accuracy of ±2.5% RH•Temperature compensated •Temperature output option •Two-point field calibration •NIST traceable calibrations
loopmax = (V
supply - 9.5)/0.02 AMPS). Accuracy: Includes linearity, hysteresis, repeatability, and voltage effects. Humidity: ±2.5% from 10% to 80% RH @ 25°C, ±3.5% from 80% to 90% RH @ 25°C.Temperature: ±0.5°F(0.27°C) @ 77°F (25°C) or +/- 0.75% of span,whichever is greater. Adjustments: Zero and Span field adjustments, non-interacting. Time Constant: 50 seconds in slow moving air. Connections: Screw terminals (22-14 AWG wire). Weight: 6 1 lbs (27 6 g). AH740.54 lbs (245 g). AH750. Min. output current: 3.8 mA. Max. output current: 22 mA. Filter: 6 0 micron stainless-steel sintered filter(replacement P/N : AC103512) Factory Mutual Approvals:

Applications

Intrinsically safe:Suitable for the following hazardous area locations: Class I, Division 1, Groups A, B, C, D Class I, Zone 0, AEx ia IIC T4Non-Incendive:Suitable for the following hazardous area locations: Class I, Division 2, Groups A, B, C, D Building automation systems (HVAC), hospitals, foodstorage,warehouses, clean rooms, pharmaceutical, drying equipment, and emissions monitoring. Transmitter entity parameters: V

Specifications

Humidity: 4 to 20 mA DC = 0% to 100% RH. Temperature: 4 to 20 mA DC over specified range (optional). Output(s): Humidity Range: 0 – 100% RH Sensing Element: Humidity: Thin film capacitive element. Temperature: 1000 ohm platinum RTD.
max = 28 volts; I
max = 100 mA; C
i = 0.037 µ F and L
i = 0 mH.
Specifications subject to change Page 9-12

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