The TR1000 is a versatile solid state/metal oxide (MOS) gas sensor that can be configured to measure a wide variety of gases and refrigerants (ammonia, R22 & R134a). This sensor is one of the most cost  effective gas sensing products available today that provides a 4-20 mA output. For applications where you need a relay output to activate fans or alarms consider the CT1000, or CT2100 (dual gas)

Applications

cold storage

food processing

commercial freezers

Transmitter Ammonia

Temp Range: -4 to 122°F (-20 to 50°C)

Output: 4-20 mA (non linear) user must specify high and low control/alarm points

Power: 12-30 VDC

Measures: 0-100 ppm

Calibration: 1 year recommended